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OUTLINE Structure and characteristics of water as a component of plant cells Functions and properties of water in plants Movement and role of water in the plant body Water potential and its measurement methodology COLLEGE OF ARTS & SCIENCES...

OUTLINE Structure and characteristics of water as a component of plant cells Functions and properties of water in plants Movement and role of water in the plant body Water potential and its measurement methodology COLLEGE OF ARTS & SCIENCES Department of Languages & Literature INTRODUCTION Did you know? Plants are primarily made up of water, often constituting 80-95% of their total mass Water is essential for plant survival and growth Water is vital for photosynthesis, respiration, absorption of minerals and nutrients, metabolism and maintain soil temperature STRUCTURE AND CHARACTERISTICS OF WATER AS A COMPONENT OF PLANT CELL Chemical Composition Water is a compound composed of two hydrogen atoms and one oxygen atom Polar nature of water molecules ○ ability to form hydrogen bonds ○ act as a solvent STRUCTURE AND CHARACTERISTICS OF WATER AS A COMPONENT OF PLANT CELL *Molecular Structure *Water (H2O) has a bent molecular geometry. ○ Three atoms (two hydrogen and one oxygen) are not arranged in a straight line, but rather form an angle of approximately 104.5 degrees. *Why is it bent? Primarily due to the repulsion between electron pairs around the central oxygen atom. This repulsion is explained by VSEPR (Valence Shell Electron Pair Repulsion) theory STRUCTURE AND CHARACTERISTICS OF WATER AS A COMPONENT OF PLANT CELL Hydrogen Bonding in Water Molecule ○ The arrangement of hydrogen atoms around the oxygen atom in water creates a polar molecule, with one side having a negative charge and the other having a positive charge. ○ This polarity causes water molecules to be attracted to each other, forming strong hydrogen bonds. STRUCTURE AND CHARACTERISTICS OF WATER AS A COMPONENT OF PLANT CELL Effects of Hydrogen Bonding in Water Molecules ○ Solvent properties: Makes water an excellent solvent. ○ Cohesion: Hydrogen bonding causes water molecules to stay close to each other which makes water a highly cohesive substance. ○ Surface Tension: property that allows a substance to resist tension and prevent rupture. ○ Adhesion ○ Capillarity: tendency of water to climb up a surface against the force of gravity due to its adhesive property. FUNCTIONS AND PROPERTIES OF WATER IN PLANTS Thermal Properties of Water High Specific Heat Capacity - The amount of heat required to raise the temperature of one gram of a substance by one degree Celsius. Significance for Plants: ○ Temperature Regulation: Water's high specific heat capacity helps plants maintain a relatively stable internal temperature, even in fluctuating external conditions. ○ Protection from Extreme Temperatures: This property acts as a buffer against sudden temperature changes, preventing damage to plant tissues. FUNCTIONS AND PROPERTIES OF WATER IN PLANTS High Latent Heat of Vaporization -The amount of heat required to vaporize one gram of a substance at its boiling point. Significance for Plants: ○ Transpiration: Water's high latent heat of vaporization is crucial for transpiration, the process by which plants lose water through their leaves. This process helps cool the plant and transports water and minerals throughout its tissues. ○ Evaporation Cooling: As water evaporates from a plant's leaves, it absorbs a significant amount of heat, cooling the plant. FUNCTIONS AND PROPERTIES OF WATER IN PLANTS High Latent Heat of Fusion -The amount of heat required to melt one gram of a substance at its freezing point. Significance for Plants: Ice Formation: Although less common in most plant environments, water's high latent heat of fusion can be important in regions where temperatures drop below freezing. It requires a significant amount of heat to convert ice back into liquid water, which can protect plant tissues from frost damage. PHYSICAL PROPERTIES OF WATER Cohesion ○ attraction between water molecules due to hydrogen bonding. ○ allows water molecules to stick together, creating a continuous column of water within plant xylem vessels. PHYSICAL PROPERTIES OF WATER Adhesion o attraction between water molecules and other substances, such as the walls of xylem vessels. ○ allows water to "stick" to the hydrophilic surfaces of plant tissues, facilitating upward movement against gravity. ○ works in conjunction with cohesion to support capillary action, which is vital for transporting water and nutrients throughout the plant. PHYSICAL PROPERTIES OF WATER Surface Tension ○ elastic tendency of liquid surfaces to minimize their surface area ○ behaving as if covered by a stretched elastic membrane. ○ causes water to form droplets on leaves ○ enables small insects, like water striders, to walk on the surface without sinking PHYSICAL PROPERTIES OF WATER High Tensile Strength ○ maximum amount of tension or pulling force that a continuous column of liquid can withstand without breaking MOVEMENT AND ROLE OF WATER IN PLANT BODY Processes involved when water moves through the plant Diffusion- movement of a substance from an area of high concentration to an area of low concentration ○ Water Diffusion: In the root water will diffuse from the soil water through the cell walls of the root hairs and across the cell walls of the cortex MOVEMENT AND ROLE OF WATER IN PLANT BODY Osmosis movement of water from an area of high concentration to an area of low concentration across a semi- permeable membrane. In the root, water will travel across the cell membrane (which is semi permeable) as long as there is a favourable concentration gradient into the cytoplasm of the cell. MOVEMENT AND ROLE OF WATER IN PLANT BODY Transpiration The loss of water vapour from the plant into the atmosphere by evaporation, through the stomata of the leaves and across the leaf surface. THE PATHWAY OF WATER ○Root absorption and movement Water is absorbed from the soil by root hairs through osmosis (symplast pathway) and diffusion (apoplast pathway). Water travels through the root cortex and endodermis, encountering the Casparian strip, which forces it to enter the symplast pathway. Water builds up in cells near the endodermis due to the impermeable Casparian strip, creating root pressure that can push water upwards. THE PATHWAY OF WATER ○ Xylem Transport Water forms unbroken columns in the xylem tissue, pulled upwards by transpiration. Cohesion-tension theory, capillarity, and adhesion forces help the water rise. THE PATHWAY OF WATER ○ Leaf Movement and Transpiration Water moves from xylem vessels into leaf cells through osmosis and diffusion. Water evaporates into the air spaces of the leaf. If stomata are open, water vapor diffuses from the leaf into the atmosphere, creating a transpiration pull. ROLE OF WATER IN THE PLANT BODY ○ ‘Plump’ cells which is called turgor pressure hold the plant erect by inflating cells. ○ Water is an ingredient for photosynthesis. ○ Water is a solvent for nutrients and products of photosynthesis ○ Water transports hormones and regulates growth ○ In fleshy fruits water assists seed dispersal ○ Water cools the leaves as it evaporates ○ Water allows storage of waste products in the vacuole in solution WATER POTENTIAL AND ITS MEASUREMENT METHODOLOGY What is Water Potential? · The force responsible for movement of water in a system · Represented by the Greek letter psi (Ψ) · Is measured in bars or megapascals · Useful measurement to determine water-deficit stress in plants · Water will move from areas of high water potential to areas of low water potential · Determined by solute concentration and pressure WATER POTENTIAL FORMULA · Ѱ=Ѱs + Ѱp · Ѱ= water potential · Ѱs= solute potential · Ѱp= pressure potential COMPONENTS OF WATER POTENTIAL · Solute potential (also called osmotic potential) Ѱs · Pressure Potential Ѱp Solute Potential · Solute Concentration · Pure water has a solute potential of zero · As solute is added the water potential of a solution drops, and water will tend to move into the solution Pressure Potential · Pressure can come from the plant’s cell wall and roots · An increase in pressure raises water potential · When water enters a plant cell, its volume increases, and the living part of the cell presses on the cell wall · The cell wall gives very little and so pressure starts to build up inside the cell · This has tendency to stop more water entering the cell and also stops the cell from bursting · When a plant cell is fully inflated with water, it is called turgid · Pressure potential is called turgor pressure in plants  MEASUREMENT METHODOLOGIES OF WATER POTENTIAL PRESSURE CHAMBER 1. Pressure Chamber (Scholander Pressure Bomb) -used to measure water potential in plants, especially in leaves and stems -A plant sample (leaf or stem) is enclosed in a chamber, and pressure is applied to push water out of the xylem. The pressure required to bring water to the surface corresponds to the water potential of the tissue. -Advantages: simple and direct for measuring plant water potential OSMOMETER 2. Osmometer - measures the osmotic potential of a solution, which is a component of water potential. - -often used to measure the water potential of solutions or cell extracts. PSYCHOMETERS Psychrometers - measures water potential based on the relative humidity of the air in equilibrium with a sample (e.g., leaf, soil). Two main types *Chilled-mirror psychrometer: Measures dew point depression *Thermocouple psychrometer: Measures the cooling effect of evaporation to determine water potential. Advantages: Can be used on variety of samples (leaves, soil, seeds Disadvantages: Requires carefule calibration and precise temperature control PLASMOLYTIC METHOD Cellosmotic potential can be measured by this technique Method involves observing the behavior of plant cells in solutions of varying concentrations. By measuring the concentration of a solution that causes the protoplasm of a plant cell to shrink away from the cell wall (plasmolysis), we can indirectly estimate the osmotic potential of the cell's cytoplasm. VAPOR PRESSURE OSMOMETER Device used to measure the osmotic potential of a solution. It works on the principle that the vapor pressure of a solution is lower than that of pure water due to the presence of solutes.  ADINA, FRITZIE CHINA BUNGCAYAO, KIRKE MICKEAL P. GAPUSAN, JUSTINE RIZEL D. GROUP 5 COLLEGE OF ARTS & SCIENCES Department of Languages & Literature Get in Touch With Us Send us a message or visit us City of Batac, Ilocos Norte, Philippines (63) 77-600-0459 [email protected] Follow us for updates facebook.com/MMSUofficial www.mmsu.edu.ph LESSON 4: MINERAL NUTRIENTS AND THEIR ABSORPTION MECHANISMS IN THE PLANT BODY PRESENTATION 2024 TOPICS Essential macro and micro 01 nutrients in the plant body Determining the essentiality of 02 a nutrient Function of macro and micro 03 nutrients in the plant body Mobility of nutrients in plant 04 tissue 01 Essential macro and micro nutrients in the plant body MACRONUTRIENTS utilized by plants in LARGE amounts. present in plant tissue in the range of 0.2 - 4.0 % (dry matter weight basis). PRIMARY MACRONUTRIENTS SECONDARY MACRONUTRIENTS PRIMARY MACRONUTRIENTS required in largest amounts SECONDARY MACRONUTRIENTS required in moderate amount MICRONUTRIENTS required by plants in much lesser quantities (less than 0.02% by dry weight). also called trace minerals essential for plant growth. MICRONUTRIENTS required in tiny amounts 02 Determining the essentiality of a nutrient  CRITERIA FOR THE ESSENTIALITY OF NUTRIENTS IN PLANTS 1. Necessary for Life Cycle Completion The absence of essential elements hinders the plant from completing its life cycle and leads to visible deficiency symptoms. 2. Non-Substitutable These elements cannot be replaced by other elements, even if they have similar properties. 3. Key Role in Metabolism Essential elements are directly involved in vital metabolic processes within the plant. 4. Seed Viability Without essential elements, plants are unable to produce viable seeds. 5. Component of Important Molecules Essential elements form part of critical plant compounds, like Mg²⁺ in chlorophyll. Bhatla, S. C., & Lal, M. A. (2023). Plant physiology, development and metabolism (2nd ed.). Springer Singapore. https://doi.org/10.1007/978-981-99-5736-1  EXPERIMENTAL APPROACHES TO DETERMINE ESSENTIALITY Hydroponics and Nutrient Deficiency Trials Nutrient Reintroduction Studies Radioisotope Tracing Genetic Studies Bhatla, S. C., & Lal, M. A. (2023). Plant physiology, development and metabolism (2nd ed.). Springer Singapore. https://doi.org/10.1007/978-981-99-5736-1 03 Function of macro and micro nutrients in the plant body  PRIMARY MACRONUTRIENTS CARBON On average, the dry weight (excluding water) of a cell is comprised of 50 percent Carbon. Serves as the backbone of many biomolecules such as starch and cellulose (the main structural component of plant cell wall). Cellulose Structure It is fixed as photo-assimilate through photosynthesis usign carbon dioxide drawn from the atmosphere. Source: Bhatla, S.C. & Lal, M.A. (2023). Plant Physiology, Development, and Metabolism 2nd Edition.  PRIMARY MACRONUTRIENTS HYDROGEN Plays central role in plant metabolism and is necessary for the synthesis of sugars. In its oxidized form (combines with Oxygen), it creates proton gradient which in turn regulates electron transport chain in photosynthesis and respiration. OXYGEN Present in all organic compounds of living organisms. Free oxygen is primarily involved as an electron acceptor in cellular respiration. Source: Bhatla, S.C. & Lal, M.A. (2023). Plant Physiology, Development, and Metabolism 2nd Edition.  PRIMARY MACRONUTRIENTS NITROGEN The next most abundant element in plant cells. A major component of proteins, enzymes, hormones, chlorophyll, amino acids, and nitrogenous bases. Functions in enhancing seed and fruit production, and improves leaf and forage crop production. PHOSPHORUS It is a structural component of ATP which is synthesized during light reaction in photosynthesis. Required as phosphate in sugar; as ester in DNA, RNA, and as phospholipids in membrane. Functions for the rapid growth of plants, encourages blooming and root growth. Source: Bhatla, S.C. & Lal, M.A. (2023). Plant Physiology, Development, and Metabolism 2nd Edition.  PRIMARY MACRONUTRIENTS POTASSIUM Activator of enzymes used in photosynthesis and respiration. Regulates the opening and closing of stomata. Reduces water loss from the leaves, increases drought tolerance, and maintains turgidity of the cell. Helps in the build-up of proteins and fruit quality and disease resistance. Source: Bhatla, S.C. & Lal, M.A. (2023). Plant Physiology, Development, and Metabolism 2nd Edition.  SECONDARY MACRONUTRIENTS SULFUR Constituent of amino acids (cysteine and methionine); vitamins (thiamine and biotin); and coenzyme A (required in respiration) Biogenesis of chloroplasts. Functions in improving root growth and seed production. Helps with vigorous plant growth and resistance to cold. CALCIUM Essential constituent of plant cell wall. Maintenance of membrane structure and permeability. Regulates fruit quality and protects the plant against heat stress and disease. Source: Bhatla, S.C. & Lal, M.A. (2023). Plant Physiology, Development, and Metabolism 2nd Edition.  SECONDARY MACRONUTRIENTS MAGNESIUM Constituent of chlorophyll molecules. Activator of the enzymes Ribulose Biphosphate Carboxylase (RuBisCo) and Phosphoenolpyruvate Carboxylase (PEP carboxylase) that are involved in dark reaction in photosynthesis. Fucntions in the nutrient uptake control and root formation in plants. Source: Bhatla, S.C. & Lal, M.A. (2023). Plant Physiology, Development, and Metabolism 2nd Edition.  MICRONUTRIENTS IRON Required in the synthesis of chlorophyll. Required in the synthesis of ferredoxin and cytochromes - proteins that carry electrons during photosynthesis and respiration. Serves as an enzyme cofactor and activates catalase and peroxidase. Functions in providing resistance against plant pathogens. MOLYBDENUM Serves as a cofactor of enzymes invovled in nitrogen metabolism. A constituent of nitrate reductase enzyme which reduces nitrate ions to nitrite ions. Functions in optimizing plant growth, aids in nodule formation in leguminous crops. Source: Bhatla, S.C. & Lal, M.A. (2023). Plant Physiology, Development, and Metabolism 2nd Edition.  MICRONUTRIENTS BORON Required in maintaining structural stability of cell wall. Involved in sugar translocation. Essential element in seed and fruit development. Functions in promoting maturity, essential for pollen grain formation and pollen tube elongation. COPPER Important component of the electron transport chain in photposynthesis. Involved in the production of lignin - an organic polymer abundant in cell walls that privides structure and support. A component of oxidase enzymes and plastocyanin. Aids in root metabolism and provides resistance against plant pathogens. Source: Bhatla, S.C. & Lal, M.A. (2023). Plant Physiology, Development, and Metabolism 2nd Edition.  MICRONUTRIENTS MANGANESE Required in chloroplast development. Activates enzymes of photosynthesis, respiration, and nitrogen metabolism. Accelerates seed germination and amturity. Increases the availability of phosphate and calcium. ZINC Required in chlorophyll formation and prevents its desctruction. Regulates the transformation of carbohydrates and consumption of sugars. Maintains the structure and function ofDNA transcription factors. Provides resistance against plant pathogens. Source: Bhatla, S.C. & Lal, M.A. (2023). Plant Physiology, Development, and Metabolism 2nd Edition.  MICRONUTRIENTS CHLORINE Essential for the photolysis of water leading ot oxygen evolution during photosynthesis. Essential for roots, cell division, and maintains ionic balance in cells. Reguilates stomatal movement. NICKEL Essential for the activation or urease - an enzyme involved in nitrogen metabolism. Functions in increasing crop yield. Source: Bhatla, S.C. & Lal, M.A. (2023). Plant Physiology, Development, and Metabolism 2nd Edition. 04 Mobility of nutrients in plant tissue  MOBILITY OF NUTRIENTS IN PLANT TISSUE Why is nutrient mobility important? It allows plants to efficiently distribute essential elements to different parts of their bodies, ensuring proper growth, development, and function This includes processes like photosynthesis, respiration, cell division, and fruit production Source: Bhatla, S.C. & Lal, M.A. (2023). Plant Physiology, Development, and Metabolism 2nd Edition.  MOBILITY OF NUTRIENTS IN PLANT TISSUE Factors Affecting Nutrient Mobility Nutrient Form: The chemical form of a nutrient can significantly influence its mobility. For example, nitrate (NO3-) is more mobile in soil and plants than ammonium (NH4+). Plant Species: Different plant species have varying abilities to absorb and translocate nutrients. Some plants are more efficient at mobilizing certain nutrients than others. Environmental Factors: Environmental conditions like temperature, pH, and water availability can impact nutrient mobility. For instance, low soil temperatures can hinder nutrient uptake, while high pH levels can reduce the availability of certain nutrients. Source: Bhatla, S.C. & Lal, M.A. (2023). Plant Physiology, Development, and Metabolism 2nd Edition.  MOBILITY OF NUTRIENTS IN PLANT TISSUE Mobility of Major Nutrients Mobile Nutrients: can be easily translocated within the plant from older leaves to younger tissues. These include nitrogen (N), phosphorus (P), potassium (K), magnesium (Mg), and molybdenum (Mo) Immobile Nutrients: have limited movement within the plant. When a deficiency occurs, the plant cannot readily relocate these nutrients from older tissues to newer growth. These include calcium (Ca), iron (Fe), zinc (Zn), copper (Cu), boron (B), and manganese (Mn) Source: Bhatla, S.C. & Lal, M.A. (2023). Plant Physiology, Development, and Metabolism 2nd Edition. Source: Bhatla, S.C. & Lal, M.A. (2023). Plant Physiology, Development, and Metabolism 2nd Edition.  MOBILITY OF NUTRIENTS IN PLANT TISSUE Impact of Nutrient Mobility on Plant Growth Nutrient Deficiency Symptoms: The mobility of a nutrient influences where deficiency symptoms appear on the plant. Mobile nutrient deficiencies often manifest in older leaves first, as the plant relocates the nutrient from older tissues to younger, growing tissues. Immobile nutrient deficiencies, on the other hand, appear in younger leaves because the plant cannot easily redistribute these nutrients. Source: Bhatla, S.C. & Lal, M.A. (2023). Plant Physiology, Development, and Metabolism 2nd Edition.  MOBILITY OF NUTRIENTS IN PLANT TISSUE Impact of Nutrient Mobility on Plant Growth Nutrient Redistribution: Plants can redistribute mobile nutrients from older leaves to younger tissues during periods of stress, such as drought or nutrient deficiency. This process, called remobilization, helps the plant prioritize growth in new tissues. Source: Bhatla, S.C. & Lal, M.A. (2023). Plant Physiology, Development, and Metabolism 2nd Edition.  MOBILITY OF NUTRIENTS IN PLANT TISSUE Impact of Nutrient Mobility on Plant Growth Nutrient Management Strategies: Understanding nutrient mobility can inform fertilization practices. For example, mobile nutrient deficiencies can be addressed by applying fertilizers to the soil, while immobile nutrient deficiencies may require foliar applications to directly deliver the nutrient to affected leaves. Source: Bhatla, S.C. & Lal, M.A. (2023). Plant Physiology, Development, and Metabolism 2nd Edition.  MOBILITY OF NUTRIENTS IN PLANT TISSUE Applications of Nutrient Mobility Knowledge Crop Production: Knowledge of nutrient mobility can be used to optimize crop yields and nutrient use efficiency. By understanding which nutrients are mobile and which are immobile, growers can tailor fertilization programs to meet the specific needs of their crops. Environmental Sustainability: Understanding nutrient mobility can contribute to environmental sustainability by reducing fertilizer use and minimizing nutrient runoff into waterways. Source: Bhatla, S.C. & Lal, M.A. (2023). Plant Physiology, Development, and Metabolism 2nd Edition.  MOBILITY OF NUTRIENTS IN PLANT TISSUE Applications of Nutrient Mobility Knowledge Plant Breeding: Plant breeders can use knowledge of nutrient mobility to develop cultivars with improved nutrient uptake and utilization. This can lead to crops that are more resilient to nutrient deficiencies and require less fertilizer. Source: Bhatla, S.C. & Lal, M.A. (2023). Plant Physiology, Development, and Metabolism 2nd Edition. Thank you! Presentation by: Kristine Genesis Bacnat Carlo Paolo Dela Cruz Franchezka Yda Manglal-lan  Topic 5 PLANT MINERAL NUTRIENT DEFIENCY BS in Biology 4B Althea Gay Pagurayan Desiree Kyle Sabado Althea Grace Vertido Physiological role of macronutrients and symptoms of their deficiency 1.Nitrogen 5. Phosphorus 2.Potassium 6. Sulfur​ 3.Calcium 7. Silicon 4.Magnesium Nitrogen Potassium - Chlorosis of older leaves - Mottled or marginal chlorosis, which then develops into necrosis primarily at the leaf tips, at the margins, and between veins - Curling and crinkling of leaves - Plants appear slender and weak Calcium Magnesium - Leaves dry at the top - Chlorosis between the leaf veins, - General chlorosis and downward occurring first in the older leaves hooking of the young leaves. - Leaves may become yellow or white - Root system may appear brownish, - Premature leaf abscission. short and highly branched Phosphorus Sulfur - Stunted growth in young plants - Chlorosis of young leaves - Dark green coloration of the leaves, - Stunting of growth, and anthocyanin which may be malformed and contain accumulation. small spots of dead tissue called necrotic spots - Production of slender stems and the death of older leaves Silicon - Susceptible to lodging (falling over) and fungal infection. Physiological role of micronutrients and symptoms of their deficiency 1. Iron 6. Copper 2. Manganese 7. Zinc 3. Boron 8. Chlorine 4. Molybdenum 9. Sodium 5. Cobalt 1. Iron 2. Manganese - Fe is essential in the heme enzyme system - Chlorosis and necrotic spotting are in plant metabolism (photosynthesis and common symptoms. respiration). It is also essential in the - Newly emerging leaves exhibit a synthesis and maintenance of chlorophyll in diffused interveinal chlorosis with plants. poorly defined green areas around - Light green to yellow interveinal chlorosis on the veins. newly emerging leaves and young shoots. 3. Boron - B has been associated with lignin synthesis, activities of certain enzymes, seed and cell wall formation, and sugar transport. - Leaf buds are discolored. They will break and drop eventually. - Plants become stunted and deformed. Proliferation of side shoots known as ‘witches broom’ can be observed as the main stem falls to ensure the growth of the lateral shoot stays dormat - Loss of apical dominance. 4. Molybdenum - Mo is a necessary component of two major enzymes in plants, nitrate reductase and nitrogenase, which 51 Plant Nutrient Management in Hawaii’s Soils are required for normal assimilation of N. - Older and middle leaves become chlorotic, and the leaf margins roll inwards. - Deficient plants are stunted, and flower formation may be restricted. 5. Cobalt - required for nitrogen fixation in legumes and in root nodules of nonlegumes. - Co plays a vital role in interaction with iron (Fe), nickel (Ni), and zinc (Zn) in maintaining cellular homeostasis. - High levels of Co result in pale-colored leaves, discolored veins, and the loss of leaves and can also cause iron deficiency in plants. 6. Copper 7. Zinc - Cu may have a role in the - Zn is required in the synthesis of synthesis and/or stability of tryptophan, which in turn is chlorophyll and other plant necessary for the formation of pigments. indole acetic acid in plants. - Reduced growth, distortion of the - Interveinal chlorosis occurs on younger leaves, and possible younger leaves, appearing as necrosis of the apical meristem. banding at the basal part of the leaf. 8. Chlorine 9. Sodium - Cl is essential in photosynthesis, where - involved in osmotic (water it is involved in the evolution of oxygen, movement) and ionic balance in increases cell osmotic pressure and the plants. water content of plant tissues. - Leaves become chlorotic and in - Chlorosis of younger leaves and wilting severe cases the margins and tips of the plant. become necrotic. Adequacy of nutrients in plant tissues Plant tissue analysis A diagnostic tool to monitor the levels of nutrient elements necessary for plant growth. 1. plant growth or yield 2. nutrient concentration of plant tissue Adequacy of nutrients in plant tissues If the nutrient concentration of plant tissue is: 1.Too low – nutrient is DEFICIENT 2.Too high – nutrient is TOXIC 3.At the midrange – nutrient is ADEQUATE Adequacy of nutrients in plant tissues DEPENDENT VARIABLE: plant growth or yield INDEPENDENT VARIABLE: nutrient concentration of plant tissue RELATIONSHIP In deficiency zone, nutrient availability is directly related to the plant's growth or yield. Nutrient availability increases with plant's growth or yield. Adequacy of nutrients in plant tissues DEPENDENT VARIABLE: plant growth or yield INDEPENDENT VARIABLE: nutrient concentration of plant tissue The transition between the deficiency and adequate zones reveals the critical concentration of the nutrient. This refers to the minimum tissue content of the nutrient just below the plant's maximum growth or yield. Adequacy of nutrients in plant tissues DEPENDENT VARIABLE: plant growth or yield INDEPENDENT VARIABLE: nutrient concentration of plant tissue RELATIONSHIP In adequate zone, increase in nutrient availability is no longer related to an increase in growth or yield. Rather, yield is constant even with increasing nutrient concentration. Adequacy of nutrients in plant tissues DEPENDENT VARIABLE: plant growth or yield INDEPENDENT VARIABLE: nutrient concentration of plant tissue RELATIONSHIP In the toxic zone, nutrient concentration is inversely related to the plant's growth or yield. Increase in nutrient concentration beyond adequate zone, decreases the plant's growth or yield. Adequacy of nutrients in plant tissues Adequacy of nutrients in plant tissues Plant tissue analysis provide information on the nutritional status of the plant, making it useful in providing corrective suggestions to avoid deficiencies or toxicities.  Topic 6 SOIL, NUTRIENT ABSORPTION AND MICROBES BS in Biology 4B Althea Gay Pagurayan Desiree Kyle Sabado Althea Grace Vertido Soil as a source of nutrients for plants Soil is a complex heterogeneous layer containing solid, liquid and gaseous phases, making it interact with mineral particles. 1. The solid phase provides a reservoir for compounds like potassium, calcium, magnesium, iron, nitrogen, phosphorus, and sulfur. Soil as a source of nutrients for plants 2. The liquid phase constitutes the soil solution, which contains dissolved mineral ions, as well as dissolved gases like oxygen, carbon dioxide, and nitrogen. It also serves as the medium for ion movement to the root surface. 3. In roots, gases are exchanged predominantly through the air gaps between soil particles. Soil as a source of nutrients for plants The soil is a complex physical, chemical and biological substrate, where the size of its particles and its cation exchange capacity allow it to be a reservoir for water and nutrients. Soil as a source of nutrients for plants Cation exchange in the soil Mineral cations such as ammonium (NH4+) and potassium (K+) adsorb to the negative surface charges of inorganic and organic soil particles, making them not easily lost when the soil is leached by water, and thus provide a nutrient reserve available to plant roots. Soil as a source of nutrients for plants Cation exchange capacity (CEC) Addition of a cation can displace another cation from its binding on the soil particle surface, making it available for uptake by the root. The degree to which a soil can adsorb and exchange ions is termed the CEC, wherein a soil with higher cation exchange capacity generally has a larger reserve of mineral nutrients. Figure 1. The principle of cation exchange on the surface of a soil particle. Soil as a source of nutrients for plants Cation exchange capacity (CEC) CEC range 1 - 10 High sand content Nitrogen and potassium more likely to leach Low water holding capacity CEC range 11-50 High clay content Higher capacity to hold nutrients at given soil depth Higher water holding capacity Source: Soil Fertility Manual, IPNI, 2006. B. Mechanism of nutrient absorption in plants 1. Root Surface Absorption: Nutrients enter the root system primarily through the root hairs and apical regions, utilizing concentration gradients and diffusion. 2. Mycorrhizal Associations: Fungal hyphae extend into the soil, increasing the surface area for nutrient absorption and accessing nutrient- depleted areas. 3. Transpiration-Driven Flow: The process of transpiration creates a negative pressure that helps draw water and dissolved minerals from the soil into the roots. Role of microbes in nutrient absorption - In their native habitat, plants are a component of a thriving ecosystem that includes a wide variety of soil microbes. a. Nitrogen. Microbes play significant roles in plant acquisition of ammonium (NH4+) and nitrate (NO3−). Ammonium is also generated by bacterial or fungal decomposition of organic debris and can be oxidized by nitrifying bacteria to nitric oxides and nitrates. b. Phosphorus. A wide variety of bacteria and fungi species are capable of solubilizing inorganic P and/or mineralizing organic P, thereby releasing bioavailable P that can be readily absorbed by plants (Pseudomonas, Bacillus and Rhizobium). c. Potassium. These microbes enhance mineral weathering under in vitro conditions and increase K solubilization in soil, mainly through acidolysis, chelation and exchange reactions, in which microbe-secreted organic acids play an important role. d. Sulfur. Many bacterial and fungal species in the rhizosphere are capable of releasing S from sulfate esters. Soil microbes can also enhance plant S nutrition through transcriptional regulation of plant sulfate assimilation pathway. e. Magnesium. Inoculation of AM fungus Funneliformis mosseae to Poncirus trifoliata seedlings resulted in enhanced growth promotion and suppression of Mg deficiency symptoms. f. Iron. Rhizosphere acidification stimulated or directly contributed by microbes facilitates plant iron acquisition. g. Copper. Fungi are capable of increasing plant fitness under Cu deficient and toxic conditions h. Manganese. Microbe-mediated rhizosphere acidification would improve plant Mn acquisition. i. Zinc. AM fungi are capable of improving plant Zn nutrition under low soil Zn conditions. j. Molybdenum. C. etunicatum strain also enhanced plant Mo concentrations in shoots and roots. k. Boron. Beneficial microbes may be applied to improve B homeostasis in plants. References: Brownell, P. (1980). Sodium as an Essential Micronutrient Element for Plants and its Possible Role in Metabolism. In Advances in botanical research (pp. 117–224). https://doi.org/10.1016/s0065- 2296(08)60088-9. Hu X, Wei X, Ling J, Chen J. Cobalt: An Essential Micronutrient for Plant Growth? Front Plant Sci. 2021 Nov 16;12:768523. doi: 10.3389/fpls.2021.768523. PMID: 34868165; PMCID: PMC8635114. Lincoln, Taiz, Møller, I. M., Murphy, A., & Zeiger, E. (2022). Plant Physiology. Singh SK, Wu X, Shao C, Zhang H. Microbial enhancement of plant nutrient acquisition. Stress Biol. 2022 Jan 10;2(1):3. doi: 10.1007/s44154-021-00027-w. PMID: 37676341; PMCID: PMC10441942. Get in Touch With Us Send us a message or visit us City of Batac, Ilocos Norte, Philippines (63) 77-600-0459 [email protected] Follow us for updates facebook.com/MMSUofficial www.mmsu.edu.ph  PHOTOSYNTHESIS AND CARBON ASSIMILATION IN PLANTS Group 7: Christian Badua Irene Evangelista Jhesryll Lagalo COLLEGE OF ARTS & SCIENCES Department of Biological Sciences  KEY CONCEPTS a. Stages of photosynthesis and the working mechanism of photosynthesis reactions b. Photosynthesis reactions and the role of photosynthesis for life c. Chloroplasts and the distribution of photosynthesis pigments d. Light reactions and energy generation mechanisms e. Factors affecting the rate of photosynthesis COLLEGE OF ARTS & SCIENCES Department of Biological Sciences Photosynthesis By definition, photosynthesis is a process wherein the light energy from the sun is converted into chemical energy, which is stored in the form of The photosynthesis reaction sugar utilized to fuel involves 2 reactants (carbon cellular activities. dioxide and water), which yield two products (oxygen and glucose). Photosynthesis At the cellular level, photosynthesis occurs in the chloroplasts. These organelles are comprised of green-colored pigment known as chlorophyll, which is responsible for the green color of the leaves of a plant. This green color pigment plays Chlorophyll is a mixture of chlorophyll-a and a vital role in photosynthesis chlorophyll-b. Besides green plants, other organisms by permitting plants to that perform photosynthesis contain various other absorb energy from forms of chlorophyll such as chlorophyll- sunlight. c1, chlorophyll-c2, chlorophyll-d, and chlorophyll-f. Stages of Photosynthesis and the Working Mechanism of Photosynthesis Reactions Presenter: Irene Evangelista  Stages of Photosynthesis: Light Dependent Reaction Photosynthesis begins with the light reaction carried out only during the day in sunlight. In plants, the light-dependent reaction takes place in the thylakoid membranes of chloroplasts.  Stages of Photosynthesis: Light Dependent Reaction Inside the thylakoid are photosystems, a membrane- bound sac-like structure that functions by gathering light. 2 Types of Photosystems 1. Photosystem II (P680) 2. Photosystem I (P700) These two photosystems differ in terms of the maximum wavelength of the light they can gather.  Light Dependent Reaction Step 1: Absorption of Light Photosystem II absorbs photons or light energy utilizing chlorophyll molecules. The absorbed light energy is passed from one pigment molecule to another until it reaches the Photosystem II or the P680. This energy excites an electron within the chlorophyll to a higher energy level, which is then captured by the primary electron acceptor, leaving the electron in the chlorophyll oxidized.  Light Dependent Reaction Step 2: Photolysis Since the chlorophyll lost The oxygen is released as a electrons, it needs to replenish byproduct into the atmosphere, those by oxidizing the water the protons accumulate inside molecule meaning the water will the thylakoid lumen, and the undergo photolysis to give off electrons are transferred to the one oxygen molecule, two chlorophyll to replace the excited hydrogen ions, and two electrons. ones. This process is catalyzed by a manganese-containing enzyme complex associated with photosystem II.  Light Dependent Reaction Step 3: Electron Transport Chain The electrons from PSII will transfer to the plastoquinone (which also picks up protons from the stroma, becoming plastoquinol PQH₂), which will shuttle them to the cytochrome b6f complex, as the electrons pass through from this complex it’s going to pump protons from the stroma into the lumen.  Light Dependent Reaction Step 3: Electron Transport Chain This results in the decrease of the proton concentration in the stroma and an increase in the proton concentration inside the thylakoid producing a concentration gradient.  Light Dependent Reaction Step 3: Electron Transport Chain The electrons will continue being transferred from the cytochrome b6f complex to plastocyanin (PC), a small, copper-containing protein that carries electrons to Photosystem I (PSI).  Light Dependent Reaction Step 4: Photosystem II Once the electrons have gone down the first leg of the electron transport chain, they arrive at PSI, where they join the chlorophyll a special pair called P700. Because electrons have lost energy before After the absorption of the their arrival at PSI, they must be photon, the photon will impart its re-energized through absorptions energy to the electrons producing of another photon. excited electrons.  Light Dependent Reaction Step 5: Electron Transport to NADP⁺ The excited electrons from the PSI are going to a series of small proteins, the first one is ferredoxin (Fd) which is an iron- sulfur protein that is going to carry the electrons to the NADP+ reductase. NADP⁺ reductase (FNR) catalyzes the transfer of electrons from ferredoxin to Outcome: NADPH NADP⁺, along with a proton from the serves as an electron stroma, forming NADPH. carrier for the Calvin Cycle.  Light Dependent Reaction Step 6: ATP Synthesis The H⁺ ions that have accumulated in This movement releases energy, the thylakoid lumen during electron which ATP synthase uses to transport create a high concentration convert ADP (adenosine of protons inside the thylakoid diphosphate) and inorganic compared to the stroma, which will phosphate (Pi) into ATP cause the H+ ions to flow back into (adenosine triphosphate). the stroma through an enzyme called This process of making ATP using ATP synthase. energy stored in a chemical gradient is called chemiosmosis.  Light Dependent Reaction Summary Product: Location: Thylakoid membrane  ATP and NADPH: These molecules store energy and reducing Events: Light energy is captured by chloroplast and power, which are essential for the stored as ATP next phase of photosynthesis (the Calvin cycle). Requires Sunlight? Yes  Oxygen: Released as a byproduct.  Stages of Photosynthesis The light-independent reactions, also known as the Calvin Cycle or "dark reactions," occur in the stroma of the chloroplast. In this reaction, it will utilize the ATP and NADPH produced in the light- dependent reactions to fix carbon dioxide (CO₂) and produce glucose.  Calvin Cycle Step 1: Carbon Fixation The first step of the Calvin cycle starts when molecules of CO2 diffuse inside the chloroplast (enters the Calvin cycle) and react with a 5-carbon molecule known as Ribulose- 1,5-biphosphate (RuBP). Wherein an enzyme called RuBisCO (Ribulose-1,5-bisphosphate carboxylase- oxygenase) catalyzes this reaction, producing a Total Carbon Calculation: Each RuBP 6-carbon molecule that is immediately split into has five carbons. With three molecules of two molecules of 3-phosphoglycerate (3- RuBP, there are 15 carbons. Adding three PGA)each with three carbons and one carbons from three CO₂ molecules, the phosphate group. total carbon count is 18. This forms six PGA molecules.  Calvin Cycle Step 2: Reduction Phosphorylation of ATP: In this step, six ATP molecules are used to add phosphate groups to the six molecules of Reduction of NADPH: Six molecules of PGA, converting them NADPH were oxidized to reduce the 1,3-BPG into 1,3- into glyceraldehyde-3-phosphate (G3P). bisphosphoglycerate (1,3- Wherein the G3P dehydrogenase catalyzed this BPG), which is facilitated reaction. by a kinase enzyme. Producing six molecules of (G3P)  Calvin Cycle Step 3: Regeneration of RuBP Regeneration of RuBP: Out of the six molecules of G3P produced after three turns of the cycle, only one G3P molecule is set aside to contribute toward forming glucose and other carbohydrates. Recycling of G3P: The remaining five G3P molecules are rearranged, using an ATP from the light reactions, and regenerate three molecules of RuBP. This allows the cycle to continue and fix more CO₂.  Calvin Cycle Step 4: Glucose Formation Three turns of the Calvin cycle are needed to make one G3P molecule that can exit the cycle and go towards making glucose.  Stages of Photosynthesis Summary Light-independent Reaction (Calvin cycle) Location: Stroma Events: ATP is used to create sugars that the plant will utilized to live Requires Sunlight? No  Calvin Cycle Summary In three turns of the Calvin cycle: ATP. 9 ATP’s are converted to 9 ADP Carbon. 3 CO2 combine with 3 RuBP (6 during the reduction step and 3 during acceptors, making 6 molecules of the regeneration step). glyceraldehyde-3-phosphate (G3P). NADPH. 6 NADPH’s are converted 1 G3P molecule exits the cycle and to 6 NADP+ (during the reduction step). goes towards making glucose. A G3P molecule contains three fixed 5 G3P molecules are recycled, carbon atoms, so it takes two G3Ps to regenerating 3 RuBP acceptor build a six-carbon glucose molecule. molecules. It would take six turns of the cycle, or 6 CO2, 18 ATP, and 12 NADPH, to produce one molecule of glucose. Photosynthesis reactions and the role of photosynthesis for life Presenter: Christian Jericko S. Badua Photosynthesis Photosynthesis is a biochemical process that converts light energy into chemical energy, primarily occurring in plants, algae, and some bacteria. It is fundamentally an oxidation–reduction reaction, as seen by examining the summary equation for photosynthesis: 6CO2 + 12H2O → C6H12O6 + 6O2 + 6H2O This indicates that carbon dioxide (CO₂) and water (H₂O) are transformed into glucose (C₆H₁₂O₆) and oxygen (O₂) using light energy. Photosynthesis Photosynthesis takes place in three stages: 1. capturing energy from sunlight; 2. using the energy to make ATP and to reduce the LIGHT-DEPENDENT compound NADP+, an electron carrier, to NADPH; REACTIONS and 3. using the ATP and NADPH to power the synthesis of LIGHT-INDEPENDENT organic molecules from CO2 in the air. REACTIONS (CALVIN CYCLE) Two Types of Reactions Light – Dependent Reactions Provide energy for the Calvin Cycle (light- independent reactions). Essential for the survival of plants and, consequently, all aerobic life forms. Take place in the thylakoid membrane and require a continuous supply of light energy. Chlorophylls absorb this light energy, which is converted into chemical energy through the formation of two compounds: - ATP, an energy storage molecule - NADPH – a reduced (electron-bearing) electron carrier. In this process, water molecules are also converted to oxygen. Key Components Involved Chlorophyll – is the pigment that absorbs light. Photosystems – have large complexes of pigment and protein molecules present within the plant cells. They are responsible for capturing light energy. A. Photosystem I - Located in the stroma lamellae and at the edges of the grana - Absorbs light at 700 nm (P700) B. Photosystem II - Located predominantly in the grana lamellae - Absorbs light at 680nm (P680) Key Components Involved Electron Transport Chain (ETC) – a series of proteins that transfer electrons. Site of Light-Dependent Reactions The internal thylakoid membrane is highly organized and contains the structures involved in the light-dependent reactions. For this reason, the reactions are also referred to as the thylakoid reactions. The thylakoid reactions take place in four stages. Stages of the Light-Dependent Reactions STAGE EVENTS Primary photoevent A photon of light is captured by a pigment. This primary photoevent excites an electron within the pigment. This excitation energy is transferred to the Charge separation reaction center, which transfers an energetic electron to an acceptor molecule, initiating electron transport. Stages of the Light-Dependent Reactions STAGE EVENTS The excited electrons are shuttled along a series of electron carrier molecules embedded within the photosynthetic Electron transport membrane. Several of them react by transporting protons across the membrane, generating a proton gradient. Eventually the electrons are used to reduce a final acceptor, NADPH. The protons that accumulate on one side of the membrane now flow back across the Chemiosmosis membrane through ATP synthase where chemiosmotic synthesis of ATP takes place, just as it does in aerobic respiration. Light-Dependent Reaction: Summary Under the light-dependent reactions, the light energy is converted to ATP and NADPH, which are used in the second phase of photosynthesis. During the light reactions, ATP and NADPH are generated by two electron-transport chains, water is used and oxygen is produced. The chemical equation in the light reaction of photosynthesis can be reduced to: 2H2O + 2NADP+ + 3ADP + 3Pi → O2 + 2NADPH + 3ATP Light-Independent Reactions Also called Calvin cycle or sometimes, the dark reaction. takes place in the stroma of the chloroplast and does not directly require light. Instead, this type of reaction uses ATP and NADPH from the light-dependent reactions to fix carbon dioxide and produce three-carbon sugars — glyceraldehyde-3-phosphate, or G3P, molecules — which join up to form glucose. Light-Independent Reactions In a series of reactions, six molecules of CO2 are bound to six RuBP by rubisco to produce 12 molecules of PGA (containing 12 × 3 = 36 carbon atoms in all, 6 from CO2 and 30 from RuBP). The 36 carbon atoms then undergo a cycle of reactions that regenerates the six molecules of RuBP used in the initial step (containing 6 × 5 = 30 carbon atoms). This leaves two molecules of glyceraldehyde 3-phosphate (G3P) (each with three carbon atoms) as the net gain. Light-Independent Reactions With 6 full turns of the cycle: - 6 molecules of carbon dioxide enter - 2 molecules of G3P are produced - 6 molecules of RuBP are regenerated. Thus six turns of the cycle produce two G3P that can be used to make a single glucose molecule. The six turns of the cycle also incorporated six CO2 molecules, providing enough carbon to synthesize glucose, although the six carbon atoms do not all end up in this molecule of glucose. Light-Independent Reactions : Summary The Calvin cycle can be thought of as divided into three phases: (1) carbon fixation, (2) reduction, and (3) regeneration of RuBP. The carbon fixation reaction generates two molecules of the 3- carbon acid PGA; PGA is then reduced to G3P by reactions that are essentially a reverse of part of glycolysis; finally, the PGA is used to regenerate RuBP. Three turns around the cycle incorporate enough carbon to produce a new molecule of G3P, and six turns incorporate enough carbon to synthesize one glucose molecule. Light-Independent Reactions : Summary Light is required indirectly for different segments of the CO2 reduction reactions. Five of the Calvin cycle enzymes—including rubisco—are light-activated; that is, they become functional or operate more efficiently in the presence of light. Glyceraldehyde 3-phosphate is a 3-carbon sugar, a key intermediate in glycolysis. Much of it is transported out of the chloroplast to the cytoplasm of the cell, where the reversal of several reactions in glycolysis allows it to be converted to fructose 6-phosphate and glucose 1-phosphate. These products can then be used to form sucrose, a major transport sugar in plants. Role of Photosynthesis for Life Oxygen Production - Photosynthesis produces oxygen as a byproduct, which is vital for the survival of most living organisms, including humans. The oxygen released during this process replenishes the atmosphere and is necessary for cellular respiration in aerobic organisms. Energy Source - Photosynthesis converts solar energy into chemical energy stored in glucose. This glucose serves as the primary energy source for plants, which are then consumed by herbivores and subsequently by carnivores, forming the basis of food webs. Without photosynthesis, there would be no primary producers to support these food chains. Role of Photosynthesis for Life Carbon Dioxide Regulation - Photosynthesis helps regulate atmospheric carbon dioxide levels by absorbing CO2 during the process. This function is critical in mitigating climate change effects by reducing greenhouse gas concentrations in the atmosphere. Nutrient Cycling - Photosynthetic organisms play a significant role in nutrient cycling within ecosystems. They extract nutrients from the soil and return them upon decomposition, thus maintaining soil fertility and ecosystem productivity.  Chloroplasts and the distribution of photosynthesis pigments Presenter: Jhesryll Lagalo Chloroplast- Photosynthetic Apparatus Occur in mesophyll cells of leaves. Chloroplasts are typically 1–2 μm thick and 5–7 μm in diameter. They are enclosed by a chloroplast envelope with a double membrane comprising outer and inner layers, separated by an intermembrane space, which hosts metabolite transport systems essential for photosynthesis. Within the chloroplast, an extensively folded third membrane, known as the thylakoid membrane, forms closed disks called thylakoids, where all chlorophyll resides. This membrane is the site of the light reactions of photosynthesis. In most higher plants, thylakoids are organized into stacks called grana (singular granum), connected by stroma lamellae—bridges extending through the stroma to adjacent grana. The thylakoid membrane surrounds the thylakoid lumen, a central aqueous space, while the surrounding stroma contains enzymes that catalyze carbon reduction reactions in photosynthesis. The stroma also houses starch granules, chloroplast DNA, RNA, and ribosomes, supporting the chloroplast’s semi-autonomous nature in producing some proteins internally, with additional proteins imported from the cytoplasm. Photosynthetic Pigments These are light sensitive pigments located in thylakoid membranes. In photosynthesis, light energy is transformed into chemical energy. This light is captured by various photosynthetic pigments. With a range of light-absorbing pigments, photosynthetic organisms can absorb a broad spectrum of wavelengths. However, each pigment generally absorbs only certain wavelengths of visible light and reflects others. The table below highlights the three main classes of photosynthetic pigments, along with their appearance and the wavelengths they absorb. Pigments Appearance Absorption Chlorophyll Green blue and orange-red Carotenoids Red/Orange/Yellow blue-green and violet Phycobilins Bluish or Reddish Green to red The absorption wavelength and characteristics of a photosynthetic pigment can be readily comprehended using a color wheel. In the color wheel representing the split spectrum of visible light, a photosynthetic pigment appears directly opposite the color it absorbs most effectively. CHLOROPHYLLS Green pigments containing Magnesium. Chief pigment required for photosynthesis. Different kinds of chlorophyll include chl-a, chl-b, chl-c, chl-d, chl-e, bacterio chlorophyll & chlorobium chlorophyll. Most Abundant Types: Chl-a and Chl-b are the most prevalent photosynthetic pigments. In plants photochemical reaction occurs only in chl-a. Chlorophylls absorb blue, violet, and red light while reflecting green light, which is why they appear green. Photosynthetic activity is maximized in red light. Structure of Chlorophyll Chlorophyll is composed of magnesium porphyrin derivatives, featuring a hydrophobic pyrole head and a hydrophilic phytol tail. The head, formed from four pyrole molecules linked by methane groups, creates a tetrapyrole or porphyrin ring with a magnesium atom at its center, bonded to the pyrole ring by two covalent and two coordinate bonds. The tail consists of a long hydrocarbon chain, and the side groups attached to the ring vary among different chlorophylls, influencing the properties of the pigments; for example, Chl-a has a methane group, while Chl-b has an aldehyde group. Chl-a appears bluish-green, while Chl-b appears olive green. Emperical formula – Chl-a – C55H72O5N4Mg. Chl-b – C55H70O6N4Mg. Varieties of Chlorophyll include – Chl-a 673, Chl-a 683, P680, P700, etc. CAROTENOIDS Fat soluble yellow, orange, brown or red pigments present in all photosynthetic plants. Contribute to autumn leaf colors alongside anthocyanins. Found in some flowers & fruits like carrot, tomato, pumpkin, etc. Act as accessory pigments, absorbing light in the blue-violet range of the spectrum Transfer captured light energy to chlorophyll, facilitating photosynthesis. Protect chlorophyll molecules from photooxidation Two types of Carotenoid Carotenes (C40H56) : Red/orange – hydrocarbons (terpenes). Common carotenes include carotenes, phytotene, lycopene, and neurosporine.. Hydrolysis of beta-carotene yields vitamin-A. Xanthophylls (C40H56O2) : Brown/yellow – oxygenated hydrocarbons, more abundant than carotenes. Differ from carotenes in having Oxygen Major xanthophylls – lutein, violaxanthin, zeaxanthin, neoxanthein. Fucoxanthin is present in diatoms and brown algae. Lutein gives yellow colour to autumn leaves. Carotenoids significant in 2 ways absorb solar energy & transmit to neighbouring pigment molecules. protect chlorophyll molecules from photooxidation. PHYCOBILINS Red or blue accessory photosynthetic pigments found in cyanobacteria & red algae. Differ from chlorophyll & carotenoids – in being water soluble. Similar to porphyrin part of chlorophylls – except that Mg is absent & tetrapyroles are linear rather than cyclic. Two major groups of phycobilins phycoerythrin red, absorb dim & blue green light that reach ocean depths. phycocyanin blue coloured – absorb orange & red light. Phycobilins enable algae to live in deep waters. Light reactions and energy generation mechanisms Presenter: Christian Jericko S. Badua Photosystem Function in Light Reactions In bacteria, a single photosystem is used that generates ATP via electron transport. This process then returns the electrons to the reaction center. For this reason, it is called cyclic photophosphorylation. In contrast, plants utilize two interconnected photosystems to enhance the efficiency of photosynthesis, overcoming the limitations of cyclic photophosphorylation. This process includes the oxidation of water and electron transfer. Photosystem Function in Light Reactions Photosystem I functions similarly to photosystems in sulfur bacteria while Photosystem II is capable of generating a high oxidation potential to oxidize water. Together, PSI and PSII facilitate a noncyclic transfer of electrons, resulting in the production of both ATP and NADPH, crucial for the plant's energy needs and metabolic processes. Photosystem Function in Light Reactions Plants use photosystems II and I in series, first one and then the other, to produce both ATP and NADPH. This two-stage process is called noncyclic photophosphorylation because the path of the electrons is not a circle—the electrons ejected from the photosystems do not return to them, but rather end up in NADPH. The photosystems are replenished with electrons obtained by splitting water. Photosystem Function in Light Reactions Photosystem II acts first. High- energy electrons generated by photosystem II are used to synthesize ATP and are then passed to photosystem I to drive the production of NADPH. For every pair of electrons obtained from a molecule of water, one molecule of NADPH and slightly more than one molecule of ATP are produced. Photosystem II The reaction center of photosystem II closely resembles the reaction center of purple bacteria. It consists of a core of 10 transmembrane protein subunits with electron transfer components and two P680 chlorophyll molecules arranged around this core. The light-harvesting antenna complex consists of molecules of chlorophyll a and accessory pigments bound to several protein chains. The reaction center of photosystem II differs from the reaction center of the purple bacteria in that it also contains four manganese atoms. These manganese atoms are essential for the oxidation of water. Photosystem II The oxidation of water in photosystem II, while not fully understood, has some emerging outlines. In this process, 4 manganese atoms are clustered together with reaction center proteins, and 2 water molecules are associated with this manganese cluster. Upon photon absorption, an electron in a P680 chlorophyll molecule is excited and transferred to an acceptor, resulting in the oxidation of P680, which then extracts an electron from a manganese atom. The oxidized manganese atoms, aided by reaction center proteins, subsequently remove electrons from the oxygen atoms of the 2 water molecules. This intricate process requires the absorption of four photons to fully oxidize the 2 water molecules, ultimately generating one molecule of O2. The role of b6-f complex The primary electron acceptor for the light-energized electrons leaving photosystem II is a quinone molecule. The reduced quinone that results from accepting a pair of electrons (plastoquinone) is a strong electron donor; it passes the excited electron pair to a proton pump called the b6-f complex embedded within the thylakoid membrane. This complex closely resembles the bc1 complex in the respiratory electron transport chain of mitochondria. Arrival of the energetic electron pair causes the b6-f complex to pump a proton into the thylakoid space. A small, copper-containing protein called plastocyanin then carries the electron pair to photosystem I. Photosystem I The reaction center of photosystem I consists of a core transmembrane complex consisting of 12 to 14 protein subunits with two bound P700 chlorophyll molecules. Energy is fed to it by an antenna complex consisting of chlorophyll a and accessory pigment molecules. Photosystem I accepts an electron from plastocyanin into the “hole” created by the exit of a light- energized electron. The absorption of a photon by photosystem I boosts the electron leaving the reaction center to a very high energy level. The electrons are passed to an iron–sulfur protein called ferredoxin. Unlike photosystem II and the bacterial photosystem, the plant photosystem I does not rely on quinones as electron acceptors. Making NADPH Photosystem I passes electrons to ferredoxin on the stromal side of the membrane (outside the thylakoid). The reduced ferredoxin carries an electron with very high potential. Two of them, from two molecules of reduced ferredoxin, are then donated to a molecule of NADP+ to form NADPH. The reaction is catalyzed by the membrane-bound enzyme NADP reductase. Because the reaction occurs on the stromal side of the membrane and involves the uptake of a proton in forming NADPH, it contributes further to the proton gradient established during photosynthetic electron transport. ATP is generated by chemiosmosis The chloroplast has ATP synthase enzymes in the thylakoid membrane that form a channel, allowing protons to cross back out into the stroma. These channels protrude like knobs on the external surface of the thylakoid membrane. As protons pass out of the thylakoid through the ATP synthase channel, ADP is phosphorylated to ATP and released into the stroma. The stroma contains the enzymes that catalyze the reactions of carbon fixation—the Calvin cycle reactions. This mechanism is the same as that seen in the mitochondrial ATP synthase, and, in fact, the two enzymes are evolutionarily related. The production of additional ATP The passage of an electron pair from water to NADPH in noncyclic photophosphorylation generates one molecule of NADPH and slightly more than one molecule of ATP. To produce the extra ATP, many plant species are capable of short-circuiting photosystem I, switching photosynthesis into a cyclic photophosphorylation mode, so that the light-excited electron leaving photosystem I is used to make ATP instead of NADPH. The energetic electrons are simply passed back to the b6-f complex, rather than passing on to NADP+. The b6-f complex pumps protons into the thylakoid space, adding to the proton gradient that drives the chemiosmotic synthesis of ATP. The relative proportions of cyclic and noncyclic photophosphorylation in these plants determine the relative amounts of ATP and NADPH available for building organic molecules. Light Reactions and Energy Generation Mechanisms: Summary Chloroplasts have two connected photosystems. Photosystem I transfers electrons to NADP+, reducing it to NADPH. Photosystem II replaces electrons lost by photosystem I. Electrons lost from photosystem II are replaced by electrons from oxidation of water, which also produces O2. The two photosystems work together in noncyclic photophosphorylation. Photosystem II and photosystem I are linked by an electron transport chain; the b6-f complex in this chain pumps protons into the thylakoid space ATP is generated by chemiosmosis. ATP synthase is a channel enzyme; as protons flow through the channel down their gradient, ADP is phosphorylated producing ATP, similar to the mechanism in mitochondria. Plants can make additional ATP by cyclic photophosphorylation. Factors Affecting the Rate of Photosynthesis Presenter: Jhesryll Lagalo Light Intensity Light intensity plays a fundamental role in photosynthesis as it drives the light-dependent reactions. At low light intensities, there is a direct proportional relationship between light intensity and photosynthesis rate – as light increases, so does the rate of photosynthesis. This occurs because more photons activate more chlorophyll molecules, leading to increased ATP and NADPH production. Different wavelengths of light affect photosynthesis differently: Photosystem I (PSI) operates most efficiently at 700 nm, while Photosystem II (PSII) works best at 680 nm. However, at very high light intensities, the rate plateaus as other factors become limiting. Excessive light can even damage chlorophyll molecules, causing a steep decline in photosynthetic rate (not shown in the graph). Temperature All biochemical and biological processes occur at an optimum range of temperature in all living organisms. Photosynthesis is also a biological process and the photosynthetic rate has been observed to rise over a temperature range of 6 to 37 degrees Celcius. The plant tissues die at 43 degrees Celcius, so there is an abrupt fall in photosynthesis. Higher temperatures also cause the denaturation of proteins, and the inactivation of enzymes involved, alternatively regulating enzymatic dark reaction of photosynthesis. Above 25-30 degrees Celsius, the rate of photosynthesis is reduced. Carbon Dioxide Concentration An increase in the carbon dioxide concentration increases the rate at which carbon is incorporated into carbohydrate in the light-independent reaction, and so the rate of photosynthesis generally increases until limited by another factor. As it is normally present in the atmosphere at very low concentrations (about 0.04%), increasing carbon dioxide concentration causes a rapid rise in the rate of photosynthesis, which eventually plateaus when the maximum rate of fixation is reached Water Supply Water is essential for photosynthesis as both a reactant and a medium for chemical reactions. When water availability decreases, plants respond by closing their stomata to prevent water loss through transpiration. This protective mechanism has a significant consequence: closed stomata prevent carbon dioxide from entering the leaf. The reduced CO₂ availability then leads to a decrease in photosynthetic rate. Plant Physiology (MBBS 1304) PRESENTED BY: GROUP 6 JEAN APRIL S. BUGUIS ALEQUE CEL LOPEZ JEWELL S. TUMAMAO MMSU BS INBIOLOGY IV-EXCHANGE STUDENT COLLEGE OF ARTS & SCIENCES Department of Biological Sciences Mineral Nutrients and Their Absorption Mechanisms in The Plant Body  LIST OF CONTENTS: a. Physiological role of macronutrients and symptoms of their deficiency b. Physiological role of micronutrients and symptoms of their deficiency c. Adequacy of nutrients in plant tissues a. Physiological Role of Macronutrients and Symptoms of Their Deficiency  Carbon (C) – "The Fundamental Builder" Physiological Role: Carbon is the main element used by plants to form organic compounds such as sugars, which are necessary for plant growth and energy storage. It is absorbed as carbon dioxide (CO₂) during photosynthesis, the process that converts sunlight into energy. If Deficient: - Deficiency is extremely rare but would result in poor photosynthesis and limited plant growth.  Hydrogen (H) – "The Water Component" Physiological Role: Hydrogen is absorbed from water (H₂O) and is essential for the creation of organic molecules. It plays a vital role in photosynthesis, energy transfer, and cell structure. If Deficient: - Lack of water leads to wilting, slower growth, and a reduction in metabolic processes.  Oxygen (O) – "The Life Sustainer" Physiological Role: Oxygen is crucial for cellular respiration, allowing plants to break down sugars to release energy needed for growth. It is absorbed from both water and air. If Deficient: - Limited oxygen availability to roots causes root rot, suffocation, and poor overall growth.  Nitrogen (N) – "The Growth Promoter" Physiological Role: Nitrogen is a key component If Deficient: of amino acids, the building blocks of proteins, which are needed for growth and development. It is - Yellowing of older leaves (chlorosis) due also a vital part of chlorophyll, the pigment to reduced chlorophyll responsible for photosynthesis, and helps plants - Stunted growth and smaller fruits and grow leaves, stems, and overall biomass. flowers Whole leaves turn yellow, starting from the lower to upper leaves.  Phosphorus (P) – "The Energy Distributor" If Deficient: Physiological Role: Phosphorus plays a central role in the formation of ATP (adenosine - Weak root systems and poor plant triphosphate), the molecule that stores and establishment transfers energy in cells. It is also critical for root development, flowering, and fruit production. - Dark green or purplish coloration in older leaves - Delayed flowering and poor seed development Purple or bronze discolouration in the upper and lower sides of older leaves.  Potassium (K) – "The Nutrient Manager" Physiological Role: Potassium regulates If Deficient: various vital processes, including water uptake, - Yellowing of leaf margins (marginal chlorosis), enzyme activation, and the movement of followed by browning (necrosis) nutrients. It helps plants withstand stress from drought, disease, and extreme temperatures, and - Weak stems, increased disease susceptibility, contributes to improving fruit quality. and reduced fruit size Browning or yellowing on leaf edges of newly matured leaves.  Calcium (Ca) – "The Structural Stabilizer" Physiological Role: Calcium is essential for If Deficient: building strong cell walls, maintaining cell integrity, and enabling nutrient transport - Deformed or irregularly shaped new leaves (often within the plant. It is vital for growing new curled or hooked) tissues such as roots, shoots, and leaves. - Blossom-end rot in fruits like tomatoes and peppers - Weak root systems and cell collapse in stems New leaves are with stunted growth as compared to the older leaves.  Magnesium (Mg) – "The Green Pigment Producer" Physiological Role: Magnesium is a central If Deficient: component of chlorophyll, the molecule that - Interveinal chlorosis in older leaves (yellowing allows plants to capture sunlight and carry out between veins) photosynthesis. It also activates many plant enzymes involved in growth processes. - Reduced quality and yield of fruits and flowers - Premature leaf drop Lower leaves are paler and chlorotic as compared to upper leaves, with dark green veins. This is known as interveinal chlorosis.  Sulfur (S) – "The Protein Builder" Physiological Role: Sulfur is necessary for the If Deficient: synthesis of proteins, enzymes, and vitamins. It aids - General yellowing of younger leaves (similar in the production of chlorophyll and supports root to nitrogen deficiency) development and seed production. - Stunted growth and poor plant development - Woody stems and small root systems Chlorotic appearance - pale green that eventually turns to a deep yellow  b. Physiological Role of Micronutrients and Symptoms of Their Deficiency  Boron (B) – "The Growth Regulator" Physiological Role: Boron supports cell wall If Deficient: formation, helps transport sugars, and is vital for flowering and seed production. It also regulates - Death of terminal buds and reduced growth of the uptake and efficient use of other nutrients. new shoots - Brittle, thickened leaves - Poor fruit set and small, deformed fruits Leaf buds are discoloured. They will break and drop eventually.  Copper (Cu) – "The Reproductive Helper" Physiological Role: Copper is important for If Deficient: reproductive growth, particularly in pollen formation and seed production. It also plays a role in - Dark green, twisted leaves chlorophyll synthesis and helps strengthen plant - Poor flowering and seed formation stems. - Wilting and stunted plant growth Leaves can take on bluish-green tint and display interveinal chlorosis, where the leaf turns yellow but the veins remain green.  Iron (Fe) – "The Chlorophyll Maker" Physiological Role: Iron is essential for the If Deficient: production of chlorophyll, the pigment - Yellowing between leaf veins (interveinal responsible for the green color of plants and for chlorosis), especially in younger leaves photosynthesis. It also plays a role in various enzyme functions. - Poor growth and reduced plant vigor - Premature leaf drop Young leaves are paler as compared to matured leaves, with dark green veins.  Manganese (Mn) – "The Enzyme Activator" Physiological Role: Manganese activates If Deficient: enzymes involved in photosynthesis, nitrogen - Yellowing between veins of younger leaves metabolism, and the formation of certain plant (interveinal chlorosis) hormones. It also plays a role in the breakdown of carbohydrates. - Reduced growth, poor fruit production, and leaf crinkling Yellowing between veins and broad green areas around veins in younger leaves.  Zinc (Zn) – "The Growth Hormone Regulator" Physiological Role: Zinc is involved in If Deficient: hormone production, especially auxins, which - Shortened internodes, leading to dwarfism are important for stem elongation and leaf expansion. It also regulates carbohydrate - Yellowing between veins in younger leaves metabolism and enzyme activation. (interveinal chlorosis) - Leaf curling and rosetting Yellowing between veins and bronze spots in younger leaves.  Molybdenum (Mo) – "The Nitrogen Fixer" Physiological Role: Molybdenum is required for If Deficient: nitrogen metabolism and the conversion of nitrates into usable forms for plant growth. It is - Pale yellow leaves that may become scorched crucial for nitrogen fixation in legumes. - Poor nitrogen utilization, leading to stunted growth - Cupping or rolling of leaves Necrosis of the leaf edges and leaves can take on a narrow or deformed appearance.  Chlorine (Cl) – "The Disease Fighter" Physiological Role: Chlorine helps regulate osmotic If Deficient: pressure, assists in photosynthesis, and enhances disease resistance. It also supports proper stomatal - Wilting, leaf spotting, and bronzing function (pores for gas exchange). - Poor root and shoot growth - Reduced plant resilience to disease Chlorotic and necrotic spotting along leaves  Cobalt (Co) – "The Nitrogen Partner" Physiological Role: Cobalt is essential for If Deficient: nitrogen fixation in legumes, helping these plants convert atmospheric nitrogen into a form they - Reduced nitrogen fixation, leading to pale, can use. It also plays a role in stimulating root stunted growth nodule development. - Poor root nodule formation in legumes Yellowing leaves and stunted growth  Silicon (Si) – "The Structural Defender" If Deficient: Physiological Role: Silicon strengthens cell walls, making plants more resistant to diseases, pests, - Weaker plants that are more susceptible to and physical stresses like lodging (falling over). It diseases and physical stress also helps improve drought tolerance. - Increased lodging in tall crops such as cereals Fragile, curling leaves  Sodium (Na) – "The Water Regulator" Physiological Role: Sodium can substitute for If Deficient: potassium in some plants, particularly in salt- tolerant species. It helps regulate water balance - Poor water regulation and wilting in salt- and supports osmotic pressure in cells. tolerant plants - Stunted growth and reduced crop yield Yellowing leaves, stunted growth, dry, brown patches on older leaves.  Nickel (Ni) – "The Seed Helper" Physiological Role: Nickel activates the If Deficient: enzyme urease, which breaks down urea into - Poor seed germination and viability usable nitrogen. It is important for seed germination and overall plant nitrogen - Necrosis (death) of leaf tips metabolism. Leaf tip burning  c. Adequacy of Nutrients in Plant Tissues  Understanding the adequacy of nutrients in plant tissues is crucial for ensuring optimal growth and development. Plant tissue analysis is used as a diagnostic tool to monitor the levels of nutrient elements necessary for plant growth. If a tissue level of a nutrient is below the lower end of the sufficiency range, the nutrient should be considered deficient, whereas if the level is above the upper end of the range, the nutrient can be considered as approaching a toxic level. The midpoint of the sufficiency range is the target to aim at. As the level approaches the lower limit, the nutrient should be added. As the level approaches the upper limit, additions of the nutrient should be withheld. It is important to be near the midpoint for most nutrients, because imbalances in the ratios of nutrients can affect crop growth.  Mechanism of Absorption of Ions and Mineral Nutrients a. Soil as a Source of Nutrients for Plants Soil Nutrient Elements Soil is a major source of nutrients for plant growth. Nutrients supplied by the soil are called mineral nutrients. The non- mineral nutrients such as carbon (C), hydrogen (H) and oxygen (O) come from air and water during photosynthesis. ✓ Soil mineral nutrients are separated into two groups the macro and micronutrients. o The macro nutrients are further broken down into two groups the primary and the intermediate nutrients. The primary nutrients are required by plants in relatively large proportions. These are the most famous; the nitrogen (N), phosphorus (P) and potassium (K) commonly referred to as NPK. The intermediate nutrients are required by plants in medium quantities, these are calcium (Ca) magnesium (Mg) and sulfur (S). o The micronutrients are required in relatively small proportions. They include the iron (Fe), boron (B), manganese (Mn), copper (Cu), zinc (Zn), molybdenum (Mo), nickel (Ni) and chlorine (Cl). It is important to note that though the soil nutrients are separated into different groups (based on the quantity required by the plant), each nutrient is equally important. A shortage of any nutrient can limit the growth and yield of a plant. This is in accordance with Liebegs law of the minimum.  Sources of soil nutrient 1. Organic matter decomposition 2. Precipitation 3. Biological nitrogen fixation 4. Inorganic fertilizer application 5. Weathering of soil rocks and minerals What affects the availability of nutrients in soil? ✓ leaching ✓ soil erosion ✓ soil pH ✓ denitrification ✓ volatilization ✓ nitrogen immobilization and crop nutrient uptake.  Soil Erosion Soil Erosion disrupts the soil structure, washes away organic matter in the soil and therefore reducing soil fertility. This often increases the need for additional and costly fertilizers to compensate for nutrient losses. Some causes of soil erosion include: 1.Soil gradient: The steeper the gradient of a soil, the more vulnerable it is to soil erosion. 2. Soil erodibility: The more erodible a soil, the more sensitive it is to erosion. This is influenced by the soil characteristic and nature. A soil that has experienced previous erosion will have higher chances of erosion. 3. Vegetative cover: Soil vegetation can protect the soil from wind or water erosion by creating vegetative cover to the soil.  Leaching This is the washing downward of nutrients in the soil below the root zone. Some of the factors influencing leaching include: 1. Mobility of nutrients: When there is sufficient water in the soil, nutrients in soil solution can be easily washed down beyond the root zone. An example is nitrogen present in the form of nitrate; a highly mobile negatively charged ion. 2. Soil texture: Leaching occurs in soils which have high water infiltration rates and low ability to hold nutrients. Examples of such are the sandy soil and clay soil.  Denitrification ✓ This process results in the gaseous loss of nitrogen to the atmosphere. ✓ Denitrification occurs in warm and anaerobic (saturated) soils usually having high nitrate levels. ✓ During this process soil microbes break Figure 1: Stages of denitrification reaction down nitrate to obtain oxygen for their respiration. The end product is nitrogen gas released to the atmosphere. ✓ Ways of avoiding loss of nitrogen through denitrification include proper timing of organic or inorganic fertilizer application; such that the soil receives it when it really needs it. Crop producers are advised to apply fertilizers in splits in order to match the crop demand for nitrogen with supply.  Volatilization ✓ This process also involves the gaseous loss of nitrogen to the atmosphere. ✓ When nitrogen fertilizers are applied in urea form (this could be inorganic fertilizers of animal manure), an enzyme urease catalyzes the reaction of urea with water resulting in ammonia gas released to the atmosphere. ✓ Volatilization occurs in warm and moist soil conditions. Volatilization also increases with high soil pH. ✓ To reduce nitrogen loss through this means, crop producers are encouraged to adapt methods of applying urea or ammonium based fertilizers below the soil surface.  b. Mechanism of Nutrient Absorption in Plants  Nutrient Uptake In most species of plants, the root system is the site of nutrient uptake. Most nutrient uptake occurs just above the growing root tip, in the region called the zone of maturation. Epidermal cells in this part of the root have extensions called root hairs. ( FIgure 36.9). Root hairs dramatically increase the surface area available for nutrient and water absorption. For example, the root system of a single annual rye plant can have a total surface area the size of a basketball court.  Nutrient Uptake Root hairs are so numerous and so efficient at absorbing nutrients from soil that, over time, they create a “zone of nutrient depletion” in soil immediately surrounding them. The formation of this mined-out region is why continued root growth is vital to a plant’s health. Because roots continue to grow throughout a plant’s life, the zone of maturation is continually entering new and potentially nutrient-rich areas of soil. If an epidermal cell encounters soil where nutrients are available, what happens? How do ions enter?  Mechanisms of Nutrient Uptake Establishing a Proton Gradient Some membrane proteins span the Plants absorb nutrients and concentrate them bilayer, however, and allow specific in their tissues. In an epidermal cell, ions such ions to cross the membrane. Because as potassium (K+), hydrogen phosphate root hairs have such a large surface (HPO42 -), and nitrate (NO3-) are many times area, they contain large numbers of membrane proteins that bring more concentrated than they are in the soil nutrients into the cytosol of root cells. water outside the cell. These membrane proteins cannot For these nutrients to be used by plants, they import the ions that the plant needs must enter root cells against a strong completely on their own, however. They often function in tandem with another concentration gradient. How is this possible? protein, a proton pump. As Figure 36.10a shows, the answer hinges on proton pumps, or H+-ATPases. Root cells use proton pumps to establish an electrochemical gradient that drives the import of essential ions into cells. These proteins are found in the plasma membranes of root epidermal and cortex cells, and they are similar to the pumps that make it possible for companion cells to load sucrose into phloem against a concentration gradient. Proton pumps in roots transport protons to the exterior of cells. The activity of proton pumps leads to an excess of protons