Crop Physiology Reviewer Midterm PDF

**CROP PHYSIOLOGY REVIEWER** **MIDTERM** **PHOTOSYNTHESIS** - chemical reaction - putting together with light - use sunlight to turn water and CO~2~ into glucose - glucose used for energy and building block for growing **Glucose --** a kind of sugar **Autotroph-** make glucose **Het...

**CROP PHYSIOLOGY REVIEWER** **MIDTERM** **PHOTOSYNTHESIS** - chemical reaction - putting together with light - use sunlight to turn water and CO~2~ into glucose - glucose used for energy and building block for growing **Glucose --** a kind of sugar **Autotroph-** make glucose **Heterotroph -** consumer **Autotrophic Process** -- make energy from sunlight. **Most Important Biological Process** - Makes organic molecules out of inorganic materials - Begins all food chains/webs - Makes O~2~ **Needed:** - Water - Carbon dioxide - Light - Chlorophyll **Two Types:** - **Anoxygenic photosynthesis** -- without production of oxygen. Not used as an electron. - **Oxygenic photosynthesis** -- water is the initial electron donor **6CO~2~ + 6H~2~O + energy → C~6~H~12~O~6~ + 6O~2~** **Significance** - Green plants possess chlorophyll which can capture, transform, translocate and store energy. - Process in which light energy turns to chemical energy. - Except green plants, no other organism can directly utilize solar energy to synthesize food. - During photosynthesis, oxygen liberated into the atmosphere makes the environment livable for all aerobic organism. - Plants and plant products are the major food source PHYSIOLOGICAL PROCESSES AFFECTING CROP PRODUCTION Growth and development of crops result from the interaction of various physiological processes, namely: ❑ Photosynthesis ❑ Respiration ❑ Transpiration ❑ Translocation These processes form the basis for crop yield. PHOTOSYNTHESIS- a chemical reaction ▪Autotrophic Process: Plants and plant-like organisms, algae, make their energy (glucose) from sunlight. ▪Stored as carbohydrate in their bodies. PHOTOSYNTHESIS is considered as the most important biological process. Why? Makes organic molecules (glucose) out of inorganic materials (carbon dioxide and water). It begins all food chains/webs. Thus all life is supported by this process. It also makes oxygen gas!! What do plants need for photosynthesis? ▪Water ▪Carbon dioxide ▪Light ▪chlorophyll Photo synthesis means \"putting together with light.\" Plants use sunlight to turn water and carbon dioxide into glucose. Glucose is a kind of sugar. Plants use glucose as food for energy and as a building block for growing. Autotrophs make glucose and heterotrophs are consumers of it. TWO TYPES OF PHOTOSYNTHESIS ▪ ANOXYGENIC PHOTOSYNTHESIS is the phototrophic process of obigate anaerobes, where light energy is captured and converted to ATP, without the production of oxygen. Water is therefore not used as an electron donor. ▪ OXYGENIC PHOTOSYNTHESIS is the most common and is seen in plants, algae and cyanobacteria. It is a non-cyclic photosynthetic electron chain where water is the initial electron donor and, as a consequence, molecular oxygen is freed as a byproduct. Photosynthesis Carbon dioxide + water oxygen sunlight glucose + absorbed by chlorophyll 6 CO 2 \+ 6 H 2 O + energy → C 6 H 12 O 6 \+ 6 O 2 SIGNIFICANCE OF PHOTOSYNTHESIS ❑Green plants possess the green pigment, chlorophyll which can capture, transform, translocate and store energy which is readily available for all forms of life on this planet. ❑Photosynthesis is a process in which light energy is converted into chemical energy. ❑Except green plants, no other organism can directly utilize solar energy to synthesize food; hence they are dependent on green plants for their survival. SIGNIFICANCE OF PHOTOSYNTHESIS ❑During photosynthesis, oxygen liberated into the atmosphere makes the environment livable for all aerobic organisms. ❑Plants and plant products are the major food sources of almost all organisms on the earth. ❑Fossil fuels like coal, gas, and oil represent the photosynthetic products of the plants belonging to early geological periods. THE PHOTOSYNTHETIC ORGAN ❑LEAF-chief site of photosynthesis. STRUCTURAL PARTS ❖upper and lower epidermis - stomates ❖mesophyll cells - chlorophyll ❖vascular bundles - transport The Mesophyll oupper side: - palisade parenchyma - regular shaped palisade cells olower side: - spongy parenchyma - irregular shaped STOMA This opening how plants exchange gases! Check it! Can you name the two important gases that go in and out of the leaves? Why are the stomata located on the underside of leaves? The photograph below is an elodea leaf (magnification X 400). Individual cells are clearly visible. The tiny green structures within the cells are chloroplasts this is where photosynthesis happens. Chloroplasts make the sugars! \"Thanks for the Glucose!\" Chloroplasts make the oxygen too! Photosynthesis Glucose provides the energy and carbon needed to make other plant materials like wax and proteins. Leaves are green because they contain the pigment: CHLOROPHYLL Leaves have a large surface area to absorb as much light as possible PHOTOSYNTHETIC PIGMENTS The photosynthetic pigments of higher plants are divided into two classes: ▪CAROTENOIDS (carotene and xanthophyll) absorb light in the regions of the spectrum not absorbed by the chlorophylls and transfer that energy to chlorophyll to be used in photosynthesis. ❑CHLOROPHYLL-the principal pigment involved in photosynthesis. It is a large molecule and absorbs light maximally in the violet blue and in the red region of the visible spectrum and reflects green light and thus leaves appear green in color. (ROYGBIV) Visible light is only a small part of the electromagnetic spectrum (all forms of light). Chlorophyll... ❑Location at the partition between two adjacent thylakoids. ❑Its basic unit is a porphyrin ring system, a structure composed of four pyrrole nuclei joined by carbon linkages. ❑The center of porphyrin is occupied by a single magnesium atom. PHOTOSYNTHETIC PIGMENTS 2 KINDS OF CHLOROPHYLL ❑chlorophyll a (bluish green)- can be found in all autotrophic organisms except photosynthetic bacteria. ❑chlorophyll b (yellowish green) RATIO: 3a:1b OTHER PIGMENTS: carotene, xanthophyll LIGHT ABSORPTION: most intense in red and blue and lowest in green ▪Absorbing Light Energy to make chemical energy: GLUCOSE! ▪Pigments: Absorb different colors of white light (ROY G BIV) ▪Main pigment: Chlorophyll a- REACTION CENTERS! ▪Accessory pigments: Chlorophyll b, xanthophyll, carotenoids- HARVESTING CENTER These pigments, that is the reaction center and the harvesting center are packed into functional clusters called photosystems ❑About 250-400 Chl-a molecules constitute a single photosystem. Two different photosystems have different forms of chlorophyll a in their reaction centres. ❑In photosystem I (PSI), chlorophyll-- a with maximum absorption at 700 nm (P700) and in photosystem II (PSII), chlorophyll-- a with peak absorption at 680 nm (P680), act as reaction centres. (P stands for pigment). ❑The primary function of the two photosystems, which interact with each other is to trap the solar energy and convert it into the chemical energy also called assimilatory power (ATP and NADPH2). ▪ PHOTOSYSTEMI PHOTOSYSTEM II Maximum Light Absorption 700 nmwavelength (P700) 680 nm wavelength (P680) Primary Electron Acceptor iron protein (Fe-S protein) PHEOPHYTIN-is a modified chlorophyll-a molecule with 2hydrogen atoms in place of magnesium ion. Electron Carriers plastocyanin, ferredoxinand cytochromes. heophytin, plastoquinone, and cytochromes. LIGHT ABSORPTION ❑In general, leaves absorb about 83% of light, while reflecting 12% and transmitting 5% ❑Of the 83% absorbed, only 4% is actually used by the plants during photosynthesis, the remainder is dissipated as heat PHOTOCHEMICAL and BIOSYNTHETIC PHASE ▪The entire process of photosynthesis takes place inside the chloroplast. Photosynthesis involves two successive steps \-\-- light reactions and dark reactions. ▪LIGHT REACTIONS- take place in the grana of the chloroplasts where chlorophyll can be found located on the membranes ▪DARK REACTIONS- take place at the stroma of the chloroplasts where it is absent from chlorophyll. LIGHT REACTION... ❑The light reaction of light dependent reaction occurs in the chloroplast of the mesophyll cells of the leaves. ❑The main purpose of the light reaction is to generate organic molecules such as ATP and NADPH which are needed for the subsequent dark reactions. LIGHT REACTION...STEPS! ❑Chlorophyll absorbs the red and blue segment of the white light and photosynthesis occurs most efficiently at these wavelengths. ❑When the light falls on the plant, the chlorophyll pigment absorbs this light and electron in it gets excited. ❑This process occurs as a photosystem. Remember photosystems?? The PSI and PSII. LIGHT REACTION...STEPS! ❑The chlorophyll pigments which are excited give up their electrons and to compensate for the loss of electrons, water is split to release four hydrogen ions and four electrons and oxygen. ❑The electrons finally reach the reaction center where they combine with NADP+ and reduce it to NADPH. ❖NADP+-Nicotinamide adenine dinucleotide phosphate. ❖NADPH-Dihydronicotinamide adenine dinucleotide phosphate. LIGHT REACTION...STEPS! ❑While the electrons are taken care of, the built up of hydrogen ions inside the thylakoid lumen is of equal importance. ❑The hydrogen ions building up inside the lumen creates a positive gradient and in the presence of the enzyme ATP synthetase, these hydrogen ions combine with ADP in the nearby region to form ATP. ❑The oxygen that is a waste product is released by the plant into the atmosphere and some of it is used in photorespiration if the plants needs to. Sun Light energy transfers to chlorophyll. At each step along the transport chain, the electrons lose energy. Chlorophyll passes energy down through the electron transport chain. Energized electrons provide energy that splits H2O H+ NADP+ NADPH to ADP oxygen released for the use in bonds P forming ATP light-independent reactions ▪In plants and simple animals, waste products are removed by diffusion. Plants, for example, excrete O2, a product of photosynthesis. LIGHT REACTION... ❑The end product of light reaction, ATP and NADPH are used to fix CO2. ❑The synthesis of ATP by the light - induced phosphorylation (addition of a phosphate group to a molecule) of ADP is known as photophosphorylation Two types of photophosphorylation are non- cyclic photophosphorylation and the Cyclic phtophosphorylation. DARK REACTION... ❑Occurs in the stroma ❑Primary process by which inorganic carbon is converted to carbon. ❑CO2 is reduced by the reducing power generated in the first step and carbohydrates are produced ❑Carbon fixation reactions produce sugar in the leaves of the plant from where it is exported to other tissues of the plant as source of both organic molecule and energy for growth and metabolism. DARK REACTION... ❑The end product of light reaction, ATP and NADPH are used to fix CO2. ❑Occur both in the presence or absence of light. ❑The end product of light reaction, ATP and NADPH are used to fix CO2. ❑The carbon dioxide fixation/ reduction into carbohydrates can occur via three pathways: DARK REACTION... 3 Pathways 1\. CALVIN BENSON CYCLE/ REDUCTIVE PENTOSE PATHWAY ❑Fixation and reduction of one molecule of CO2 requires three molecules of ATP and 2 NADPH. ❑Occurs in the mesophyll cell chloroplast ❑CO2 acceptor is RUBP ❑RUBP carboxylase enzyme is needed ❑The first stable product is 3-PGA DARK REACTION... 3 Pathways 2\. C4 OR HATCH SLACK PATHWAY- First product is 4- C oxaloacetic acid. STEPS are a\. carboxylation of PEP to OAA, PEP carboxylase is enzyme involved b\. reduction of OAA to malate or aspartate c\. decarboxylation of malate in the bundle sheath cells to form pyruvic acid d\. transfer of pyruvic acid to the mesophyll cell e\. fixation of carbon dioxide to form 3-PGA ❑Presence of KRANZ ANATOMY. DARK REACTION... 3 Pathways 3\. CAM OR CRASSULACEAN ACID METABOLISM PATHWAY operates in orchids, pineapple, other succulent plants wherein stomates are closed during the day and open during the night. FACTORS AFFECTING PHOTOSYNTHESIS Factors affecting photosynthesis can be divided into two general categories, ❑Internal ❑External (environmental) factors. INTERNAL FACTORS CHLOROPHYLL The amount of chlorophyll present has a direct relationship with the rate of photosynthesis because this pigment is directly involved in trapping light energy responsible for the light reactions. INTERNAL FACTORS LEAF AGE AND ANATOMY Newly expanding leaves show gradual increase in rate of photosynthesis and the maximum is reached when the leaves achieve full size. Chloroplast functions decline as the leaves age. Rate of photosynthesis is influenced by variation in \(i) number, structure and distribution of stomata, \(ii) size and distribution of intercellular spaces \(iii) relative proportion of palisade and spongy tissues and \(iv) (iv) thickness of cuticle. INTERNAL FACTORS DEMAND FOR PHOTOSYNTHATE : Rapidly growing plants show increased rate of photosynthesis in comparison to mature plants. EXTERNAL FACTORS Remember... CONCEPT OF LIMITING FACTORS! What are the external factors??? The major external factors which affect the rate of photosynthesis are temperature, light, carbon dioxide, water, and mineral elements. EXTERNAL FACTORS LIGHT: The rate of photosynthesis increases with increase of intensity of light within physiological limits or rate of photosynthesis is directly proportional to light intensity. EXTERNAL FACTORS TEMPERATURE: ❑Very high and very low temperature affect the rate of photosynthesis adversely. ❑Rate of photosynthesis will rise with temperature from 5°-37°C beyond which there is a rapid fall, as the enzymes involved in the process of the dark reaction are denatured at high temperature. ❑Between 5°-35°C, with every 10°C rise in temperature rate of photosynthesis doubles. EXTERNAL FACTORS EXTERNAL FACTORS CARBON DIOXIDE : ❑Since carbon dioxide being one of the raw materials for photosynthesis, its concentration affects the rate of photosynthesis markedly. ❑Because of its very low concentration (0.03%) in the atmosphere, it acts as limiting factor in natural photosynthesis. EXTERNAL FACTORS WATER ❑Water has an indirect effect on the rate of photosynthesis. ❑Loss of water in the soil is immediately felt by the leaves, which get wilted and their stomata close down thus hampering the absorption of CO2 from the atmosphere. ❑This causes decline in photosynthesis. EXTERNAL FACTORS WATER ❑Water has an indirect effect on the rate of photosynthesis. ❑Loss of water in the soil is immediately felt by the leaves, which get wilted and their stomata close down thus hampering the absorption of CO2 from the atmosphere. ❑This causes decline in photosynthesis. EXTERNAL FACTORS MINERAL ELEMENTS ❑Some mineral elements like magnesium, copper, manganese and chloride ions, which are components of photosynthetic enzymes, and magnesium as a component of chlorophylls are important. ❑Their deficiency would affect the rate of photosynthesis indirectly by affecting the synthesis of photosynthetic enzymes and chlorophyll. CHAPTER VI CELLULAR RESPIRATION: Harvesting Chemical Energy ❑Photosynthesis ends with the formation of hexose sugar. ❑Hexose can also enter into the respiratory system of the cell where it is broken down to release energy. ❑Important life processes such as synthesis of proteins, fats, and carbohydrates require a certain expenditure of energy. RESPIRATION ❑Respiration can make use of complex food materials like starch which are rich in stored energy (which holds the atoms together in the molecule) but should be converted into simpler carbohydrates like glucose. Cellular respiration and fermentation are catabolic, energy- yielding pathways CATABOLIC PATHWAYS- metabolic pathways that release stored energy by breaking down complex molecules. FERMENTATION involves no Oxygen! CELLULAR RESPIRATION where Oxygen is a reactant. AEROBIC VS. ANAEROBIC RESPIRATION Respiration is termed aerobic when oxygen is utilized and anaerobic when oxygen is not utilized. What is Cellular Respiration? ▪ Once the energy that was in sunlight is changed into chemical energy by photosynthesis , an organism has to transform the chemical energy into a form that can be used by the organism. ▪ Cellular respiration is the process that releases energy by breaking down food molecules in the presence of oxygen. Describe Cellular Respiration... ❑ The biochemical process, which occurs within cells and oxidises food to obtain energy ❑The breakdown of glucose molecules to release energy ❑Takes place in all living things ❑Is a step by step process ❑Cellular respiration occurs in the mitochondria of living cells. ❑Yields 38 ATP per glucose molecule. THE PROCESS OF CELLULAR RESPIRATION ▪ Glycolysis ▪ The Krebs Cycle ▪ The Electron Transport Chain Glycolysis and Krebs Cycle are CATABOLIC! Why? GLYCOLYSIS harvests chemical energy by oxidizing glucose to pyruvate: a closer look GLYCOLYSIS: a closer look... ❑Glycolysis means "splitting of sugar". ❑Glucose, a six-carbon sugar, is split into two 3 carbon sugars to form two molecules of pyruvate. (Pyruvate is the ionized form of a 3-C sugar, pyruvic acid) GLYCOLYSIS: a closer look... ❑This is accomplished in 10 steps each catalyzed by a specific enzymes which can be divided into two phases: ENERGY INVESTMENT PHASE and ENERGY PAYOFF PHASE. ❑ In ENERGY INVESTMENT PHASE, the cell actually spends ATP to phosphorylate the fuel molecules. ❑In ENERGY PAYOFF PHASE, ATP is produced by substrate-level phosphorylation and NAD+ is reduced to NADH. The net energy yield from glycolysis, per glucose molecule, is 2 ATP plus 2 NADH. KREBS CYCLE completes the energy yielding oxidation of organic molecules: a closer look... KREBS CYCLE: a closer look ❑Glycolysis releases less than a quarter of the chemical energy stored in glucose: most of the energy are stored in the two molecules of pyruvate. ❑If molecular oxygen is present, the pyruvate enters the mitochondrion, where the enzymes of the Krebs cycle complete the oxidation of the organic fuel. KREBS CYCLE: a closer look ❑ The pyruvic acid (a 3- carbon chain) loses a carbon through oxidation to CO2 and forms the acetyl-CoA, a 2-carbon molecule. ❑For every glucose membrane molecules (2 pyruvic acids) entering the mitochondrion, the Krebs cycle generate 6 NADH and 2 FADH2 and yield 2 ATP via substrate level phosphorylation. The Inner Mitochondrial Membrane Couples ELECTRON TRANSPORT to ATP synthesis: a closer look... ELECTRON TRANSPORT SYSTEM: a closer look... ❑Occurs in the inner mitochondrial membrane ❑NADH (from glycolysis and Krebs Cycle) and FADH2 (from Krebs cycle) are oxidized to yield ATP. ❑34 ATP is generated in ETS via oxidative phosphorylation. FACTORS AFFECTING RESPIRATION ❑AGE AND TISSUE TYPE ❖large, young tissues respire more strongly than old ❖developing tissues respire more than mature once ❖tissues undergoing metabolic processes respire more than resting tissues. FACTORS AFFECTING RESPIRATION ❑TEMPERATURE ❖enzymes activity doubles for energy 10 degrees Celcius rise in temperature within certain limits. ❖more rapid breakdown of respiration as temperature increases above 35 degree Celcius due to destruction of enzymes by heat. FACTORS AFFECTING RESPIRATION ❑OXYGEN ❖Presence of oxygen is essential for oxidative metabolism ❑CARBON DIOXIDE ❖high level (higher than normal temperature) inhibits respiration. ❖high concentration causes the stomata to close. FACTORS AFFECTING RESPIRATION ❑PHYSIOLOGICAL STATUS OF PLANT OR PLANT PARTS ❖Dormant state respire less than active parts of the plants. ❑MOISTURE CONTENT OF TISSUES ❖Seeds with higher moisture content respire more than seeds with drier tissues. TRANSPIRATION IN PLANTS CHAPTER VII WHAT IS TRANSPIRATION? ❑Transpiration is the loss of water from a plant in the form of water vapor. ❑Water is absorbed by roots from the soil and transported as a liquid to the leaves via XYLEM. ❑In the leaves, small pores allow water to escape as a vapor. Of all the water absorbed by plants, less than 5% remains in the plant for growth. TRANSPIRATION: Significance... ❑EVAPORATIVE COOLING As water evaporates or converts from a liquid to a gas at the leaf cell and atmosphere interface, energy is released. ❑ACCESSING NUTRIENTS TO THE CELL The water that enters the root contains dissolved nutrients vital to plant growth. TRANSPIRATION: Significance... ❑CARBON DIOXIDE ENTRY When a plant is transpiring, its stomata are open, allowing gas exchange between the atmosphere and the leaf. ❑WATER UPTAKE Although only less than 5% of the water taken up by roots remains in the plant, that water is vital for plant structure and function. TYPES OF TRANSPIRATION ❑CUTICULAR TRANSPIRATION Loss of water through the epidermis which is usually covered with a cuticle. In some temperate plants, about 5-10 % of the water loss from plants maybe lost from these pathway. TYPES OF TRANSPIRATION ❑LENTICULAR TRANSPIRATION Loss of water through numerous pores in the outer layer of a woody plant stem, called lenticels. In decidous species and in some fruits, water loss through lenticels maybe quite substantial. TYPES OF TRANSPIRATION ❑STOMATAL TRANSPIRATION Loss of water through stomata which can account as much as 90% of the water loss from plants. What factors affect the process of transpiration in plants? PLANT PARAMETERS These plant parameters help plants control rates of transpiration by serving as forms of resistance to water movement out of the plant. ENVIRONMENTAL CONDITION Some environmental conditions create the driving force for movement of water out of the plant. Others alter the plant's ability to control water loss. What factors affect the process of transpiration in plants?- PLANT PARAMETERS STOMATA ❑Stomata are pores in the leaf that allow gas exchange where water vapor leaves the plant and carbon dioxide enters. ❑GUARD CELLS- control each pore's opening or closing. When stomata are open, transpiration rates increase; when they are closed, transpiration rates decrease. ❑Stomata are the only way plants can control transpiration rates in the short-term. What factors affect the process of transpiration in plants?- PLANT PARAMETERS BOUNDARY LAYER ❑The boundary layer is a thin layer of still air hugging the surface of the leaf. This layer of air is not moving. ❑For transpiration to occur, water vapor leaving the stomata must diffuse through this motionless layer to reach the atmosphere where the water vapor will be removed by moving air. ❑More leaf hairs or pubescence will have larger boundary layer- SERVES AS WIND BREAK! What factors affect the process of transpiration in plants?- PLANT PARAMETERS CUTICLE ❑The cuticle is the waxy layer present on all above-ground tissue of a plant and serves as a barrier to water movement out of a leaf. ❑Cuticle is made of wax, it is very hydrophobic or 'water repelling'; therefore, water does not move through it very easily. ❑Plants from hot, dry climates and grown under direct sunlight have thicker cuticles. What factors affect the process of transpiration in plants? ENVIRONMENTAL CONDITIONS RELATIVE HUMIDITY ❑Relative humidity (RH) is the amount of water vapor in the air compared to the amount of water vapor that air could hold at a given temperature. ❑Lower RH- Higher rate of TRANSPIRATION. What factors affect the process of transpiration in plants? ENVIRONMENTAL CONDITIONS TEMPERATURE ❑Temperature greatly influences the magnitude of the driving force for water movement out of a plant. ❑As temperature increases, the water holding capacity of that air increases sharply. What factors affect the process of transpiration in plants? ENVIRONMENTAL CONDITIONS SOIL WATER ❑The source of water for transpiration comes from the soil. ❑Plants cannot continue to transpire without wilting if the soil is very dry because the water in the xylem that moves out through the leaves is not being replaced by the soil water. ❑This condition causes the leaf to lose turgor or firmness, and the stomata to close. If this loss of turgor continues throughout the plant, the plant will wilt. What factors affect the process of transpiration in plants? ENVIRONMENTAL CONDITIONS WIND ❑Wind can alter rates of transpiration by removing the boundary layer, that still layer of water vapor hugging the surface of leaves. ❑Wind increases the movement of water from the leaf surface when it reduces the boundary layer, because the path for water to reach the atmosphere is shorter. ❑Windier conditions increase transpiration because the leaf's boundary layer is smaller. What factors affect the process of transpiration in plants? ENVIRONMENTAL CONDITIONS LIGHT ❑Light has a major effect on plants. In a majority of plants, the stomata are open during the day and closed at night. When light intensity is low, transpiration is low. A diagram of a plant Description automatically generated