Plant Physiology Chapter 4 PDF

CHAPTER 4 PLANT PHYSIOLOGY By Hamizah Othman Learning Outline: At the end of this chapter, student should be able to:  define and explain the transportation in plant.  define and explain the processes of transpiration, photosynthesis, and cellular respiration. Transport...

CHAPTER 4 PLANT PHYSIOLOGY By Hamizah Othman Learning Outline: At the end of this chapter, student should be able to:  define and explain the transportation in plant.  define and explain the processes of transpiration, photosynthesis, and cellular respiration. Transportation in Plant Plants have two transportation systems of substances via two different types of transport tissue.  Xylem transports water and solutes from the roots to the leaves via TRANSPIRATION PROCESS  Phloem transports food (sugar) and amino acids from the leaves to the rest of the plant parts via TRANSLOCATION PROCESS. The vascular bundle structure: anatomy and functions in plant transport (primary growth and secondary growth)  - Are long, hollow, continuous tubes that carry water and dissolved minerals from root up XYLEM to all parts of the plant VESSELS - Contain a tough substances called lignin that lines the walls to provide support VASCULA R - Are living cells with end tubes with pores BUNDLE (sieve plates) - All cell contents have disappeared except PHLOEM the cytoplasm VESSELS - The phloem cells have companion cell near them. - Transport sucrose and amino acids from where they are used or stored a. TRANSPIRATION Transpiration is the process by which water evaporates from the leaves, which results in water being drawn up from the roots to upward. OR Is the loss of water vapor out of the leaves through stomata by diffusion. 90% of water absorbed by roots lost through transpiration  TYPES OF TRANSPIRATI ON LENTICULA CUTICULAR STOMATAL R TYPES OF TRANSPIRATION 1. CUTICULAR TRANSPIRATION: the loss of water in the form of water vapor through the cuticle Upper epidermis of leaves secretes thin layer of wax (cuticle) which minimizes loss of water Cuticle prevents evaporation of water from the leaf surface Thicker the cuticle, lesser the transpiration. 1. CUTICULAR TRANSPIRATION: 2. LENTICULAR TRANSPIRATION: the loss of water in the form of water vapor through the lenticels present in the woody stem and fruits Lenticel is small openings that develop in the older stem, and fruit Water from the cell surface evaporates and transpiration occur. It amounts of 1 – 5% of the total water loss by the plant 2. LENTICULAR TRANSPIRATION: 3. STOMATAL TRANSPIRATION: Stomata are minute pores confined to epidermis of green shoot and leaves Opening and closing of stomata are controlled by guard cells and depends on the turgidity of the guard cells. When the guard cells are turgid, pores open and close when they are flaccid. When the turgidity increases, guard cells bulge outwards widening the stomatal opening Maximum loss (80 – 90 % of the total water loss) of water from plant tissues takes place through the stomatal openings. 3. STOMATAL TRANSPIRATION:  Cooling effect -provides a Effect on mineral transport -Minerals GASEOUS EXCHANGE : It helps in significant cooling effect which that are absorbed and accumulated in the the absorption of carbon dioxide keeps the plant from being over xylem duct of the root move up and are (CO2) from the atmosphere during heated. distributed in the plant by the photosynthesis as the openings of transpiration stream. stomata in day time facilitate gaseous exchange Effect on water movement -water moves Development of mechanical tissues from the xylem vessels to -The plants become healthier and more the leaf cells and helps in compact the cell walls become thick the ascent of sap. and cutinized and the plants are able to resist the attack of fun and bacteria. IMPORTANC Increase of taste of fruits -The solutes inside E OF the cell become more Maintenance of turgidity - TRANSPIRATI concentrated when Under favourable conditions plants ON transpiration is rapid the absorb excess amount of water, concentration of sugar which is given off by transpiration solution in the cells of to maintain the optimum turgor for fruits increases and fruits better growth. taste sweeter.  Number of leaves Number of stomata INTERNAL FACTORS Size of leaf Structure of leaf FACTORS CO2 AFFECTING concentratio TRANSPIRATION n Wind and air movement Soil moisture EXTERNAL availability FACTORS Light Temperature Pressure Relative humidity INTERNAL FACTORS-transpiration FACTORS TRANSPIRATION RATE EXPLANATION NUMBER OF LEAVES High number of leaves, More leaves means larger surface higher transpiration rate area, high stomata presence, so more water loss NUMBER OF High number of stomata, More stomata means more pores, STOMATA higher transpiration rate so more water loss SIZE OF LEAVES More bigger leaves, higher Bigger leaves means bigger transpiration rate surface area, so more water loss STRUCTURE OF LEAF More cuticle, gums etc, Compact arrangement of leaf cells, lower transpiration rate presence of hairs, cuticle, and hydrophilic substances such as gums and mucilage reduce the rate of transpiration  EXTERNAL FACTORS-transpiration FACTORS TRANSPIRATION RATE EXPLANATION TEMPERATURE Increase in atmospheric This is related to opening and closing of stomata. temperature increases the rate Stomata will open when temperature rising and Vise of transpiration versa but too high temperature also close stomata PRESSURE Decrease in atmospheric During low atmospheric pressure, air will move out of pressure, increases the rate of the plant as a result of diffusion. At low pressure, the transpiration water vapor moves fast thus the rate of transpiration increases. LIGHT Increase in light intensity, This is because plants open their stomata in response increases the rate of to light, allowing water vapor to escape from the transpiration leaves. RELATIVE Increase in atmospheric It is easier for water to evaporate into dryer air than HUMIDITY humidity decrease the rate of into more saturated air. transpiration WIND More the wind velocity in the This is because high-speed winds can easily remove the atmosphere more is the rate of water vapor from the surroundings of the leaves, due to transpiration which more water vapor can be released into the atmosphere around the leaves. SOIL MOISTURE The lower the soil moisture, Sufficient availability of water in the soil allows the lower rate of transpiration stomata to remain open and thus helps transpiration to continue at a faster rate b. TRANSLOCATION  Translocation is the movement of materials from leaves to other tissues throughout the plant OR  The movement of food (sucrose and amino acids) from the sources (leaf) to sinks (developing flowers/fruits, storage organs, root) through the phloem vessels.  Plants produce carbohydrates (sugars) in their leaves by photosynthesis, but non-photosynthetic parts of the plant also require carbohydrates and other organic and nonorganic materials.  The tissue in which nutrients move is the phloem.  The phloem is arranged in long, continuous strands called vascular bundles that extend through the roots and stem and reach into the leaves as veins.  THE MASS FLOW HYPOTHESIS 1 1. At the source, sugar is loaded (active transport) into the companion cell.  It raises concentration of sugars in companion 2 cells above that in the sieve tube elements. 2. Sucrose moves from companion cells into sieve tube elements by diffusion.  This reduces the water potential of the sieve tube element. 3. Water moves into the phloem by osmosis, which increases the hydrostatic pressure.  There is a pressure gradient with high hydrostatic pressure near the source cell and 3 lower hydrostatic pressure near the sink cells. 4. Solutes move down the pressure gradient towards the sink end of the phloem.  Solutes move into sink cells and are converted 4 into other molecules (e.g. starch). 5. The removal of solutes increases the water potential at the sink end, causing water to move out of the phloem by osmosis.  Proximity of the source Regulation by INTERNAL the source/ FACTORS sink Growth hormones Water and salt FACTORS stress AFFECTING TRANLOCATION Mineral deficiency Effect of light EXTERNAL FACTORS Effect of temperature Effect of CO2 c. PHOTOSYNTHESIS Photosynthesis Photosynthesis is a process conducted by green plants in which energy from sunlight is used to convert carbon dioxide and water into organic molecules (sugars) needed for growth. Light energy is absorbed by the green pigment (chlorophyll) found in the chloroplasts. Light energy allows the production of glucose by the reaction between carbon dioxide and water. Oxygen is also produced as a waste product/ by product This reaction can be summarized in the word equation: During the process of photosynthesis, carbon dioxide from the air and water from the soil is converted into oxygen and glucose. Glucose is a sugar that can be used by the plant for respiration or converted into insoluble starch for storage.  IMPORTANCES OF PHOTOSYNTHESIS Photosynthesis is Photosynthesis helps in Photosynthesis essential for sustaining growth and provides food for all life. development of plants. The process of It converts By providing food photosynthesis atmospheric carbon (glucose) and oxygen occurs in green dioxide (given out (cellular respiration), plants which are the during respiration this will contribute to and other activities) growth and primary producers in back to oxygen. development of a food chain. It is the ultimate organism Makes organic source of oxygen molecules (glucose) and energy for all out of inorganic living organisms. materials (carbon dioxide and water). Photosynthesis Overview Photosynthesis takes place in chloroplasts. Chloroplasts are located mainly in the mesophyll cells. Each mesophyll can has 20 to 100 chloroplasts. CHLOROPLAST- site of photosynthesis semiliquid substance surrounding thylakoid membranes Chlorophyll is embedded in disk-like structure called thylakoids which are arrange into stacks. stacks of thylakoid membranes internal membrane arranged in flattened sacs  Sites of photosynthesis in plant contain a green pigment called chlorophyll that absorbs the Chlorophyll a energy from the absorbs the red and CHLOROPLA sunlight. blue light and it is ST the primary pigment 2 kinds of green in plants chlorophylls Chlorophyll b absorb only blue light and transmitted green This energy is used light thus the leaves to convert CO2 and look H2O into glucose and O2. STAGES OF PHOTOSYNTHESIS 1. LIGHT The energy-fixing reaction DEPENDENT This reaction happens when the light energy from REACTION sunlight is captured and pushed into a chemical energy called ATP. reduce NADP+ to NADPH 2. LIGHT INDEPENDENT The carbon fixing reaction use ATP and NADPH to synthesize organic REACTION/ DARK molecules (glucose) from CO2 REACTION/ CALVIN CYCLE  Two stages of photosynthesis: Light reaction & Calvin cycle Occurs in thylakoid Light Reactions: ❖Light is absorbed by chlorophyll ❖Energy from the light splits H2O ❖H from water reduces NADP (electron acceptor) to NADPH ❖Chemiosmosis makes ATP from ADP (photophosphorylation) ❖Products of light reactions: ⮚ Energy = ATP & NADPH – Calvin  Water is split Oxygen released as byprodu ct ATP and NADPH were transferred to Calvin Cycle LIGHT REACTION - RECAP Two stages of photosynthesis: Light reaction & Calvin cycle Occurs in THE CALVIN CYCLE: Stroma Also known as dark reaction/ light independent reaction CO2 from atmosphere enters chloroplast and is incorporated into organic molecules = carbon fixation NADPH from light reaction reduces the fixed carbon (by donating H) to carbohydrate ATP from light reaction is required for this step Product of calvin cycle is glucose The light-independent reactions/ the Calvin cycle can be organized into three basic stages: Carbon fixation, Reduction of 3-PGA into G3P and Regeneration RuBP In the SECOND STAGE: ATP and THE FIRST STAGE of In the LAST STAGE: NADPH are used to Calvin Cycle is carbon RuBP is regenerated, reduce 3-PGA into fixation; CO2 is fixed which enables the G3P; then ATP and from an inorganic to system to prepare for NADPH are converted an organic molecule. more CO2 to be fixed. to ADP and NADP+, respectively.  What goes OUT/ What goes IN made Carbon Glucose Dioxide ADP ATP NADP+ NADPH CALVIN CYCLE- RECAP LIGHT DEPENDENT REACTION LIGHT INDEPENDENT REACTION/ CALVIN CYCLE Both occur during daytime Both occur in chloroplast Both uses enzymes Uses sunlight/ depend on sunlight Does not need sunlight/ not depend on sunlight Occurs in grana/thylakoid membrane Occurs in stroma Uses water as substrate Carbon dioxide as substrate or fixed Oxygen as by product Glucose as product ATP and NADPH are produced ADP and NADP+ are produced Involves photolysis process Involves carbon dioxide fixation process  More light more photosynthesis LIGHT Plants have various adaptations to obtain more light For optimum photosynthesis, the temperature is between 20- 35oC TEMPERATURE High temperature (above 40oC) denatured enzymes Plant in cool region have adaptation for effective photosynthesis below 0oC. Photosynthesis rate has direct relationship to CO2 concentration with the present of optimum light and temperature. CO2 FACTORS INFLUENCE CONCENTRATIO If the concentration of CO2 in atmosphere is above N 0.03% the rate of photosynthesis will increase. PHOTOSYNTHESIS Efficiency of CO2 only up to 1.0%. At concentration higher than that, the rate will decrease because stomata closure. At higher O2 concentration the rate of photosynthesis is lower. O2 This is because O2 and CO2 are competing each other CONCENTRATIO to locate the active site of enzymes 🡪 carbon fixation N is slow The phenomenon of O2 is higher than CO2 called photorespiration Chlorophyll level/quantities is reduced when the CHLOROPHYLL plants were infected, experienced senescence's or CONCENTRATIO lack in minerals. N The leaves turned yellowish and is said as chlorotic thus the rate of photosynthesis will reduce d. CELLULAR RESPIRATION is a set of metabolic reactions and processes that take place in the cells of living organisms  to convert biochemical energy from nutrients into adenosine triphosphate (ATP),  and then release waste products (CO2)  that they require for cell division and development. OR, the biochemical pathway by which cells release energy from the chemical bonds of food molecules  and provide that energy for the essential processes of life. OR, respiration is the process of releasing energy from the breakdown of glucose. CELLULAR RESPIRATION OVERVIEW Transformation of chemical energy in food into chemical energy (ATP) cells that can be use Overall Reaction: C6H12O6 + 6O2 → 6CO2 + 6H2O The major step in respiration: 1. Glycolysis 2. Citric Acid Cycle (Krebs cycle) Aerobic cellular 3. Electron Transport Chain/Oxidative Phosphorylation respiration Breakdown of glucose (glycolysis) begins in the cytoplasm (cytosol) At this point life diverges into two forms and two pathways: Anaerobic cellular respiration (fermentation) Aerobic cellular respiration 1. Glycolysis – in cytoplasm Glycolysis is the first step in the breakdown of glucose to extract energy for cellular metabolism. 1st phase Glucose is split using ATP into 2 - G3P 2nd phase G3P is then converted to 2 pyruvate Formation of ATP and NADH 2(A). AEROBIC Cellular Respiration Oxygen required = aerobic 2 more sets of reactions which occur in mitochondria 1.Kreb’s Cycle ⮚ Occur in mitochondrial matrix ⮚ converts pyruvate via acetyl CoA into CO2; ⮚ generates NADH and FADH2 2.Electron Transport Chain ⮚ Occur in mitochondrial membranes = cristae ⮚ The NADH and FADH2 formed in the KREBS CYCLE enter the electron transport chain system. ⮚ electrons was transfers from NADH and FADH2 to reduce O2 to H2O and generate ATP 2(B). ANAEROBIC Cellular Respiration It is also known as Fermentation In anaerobic respiration, glucose is still broken down to carbon dioxide with the release of energy, but without the involvement of oxygen End products are ethanol and CO2 or lactic acid (muscle cells) Anaerobic respiration is widely used by many micro-organisms such as bacteria and yeasts also takes place in plants in the presence of little or no oxygen. The energy released by anaerobic respiration is considerably less than the energy from aerobic respiration. Equation ANAEROBIC FERMENTATION: GLUCOSE=> 2 ETHANOL + 2 CARBON DIOXIDE+ 2ATP GLUCOSE=> 2 LACTIC ACID + 2ATP FERMENTATION Glucose is not completely breakdown to CO2 and H2O because lack of oxygen. But glucose was breakdown to ethanol (plant, yeast) and CO2 OR lactic acid (certain fungi, prokaryotes, animal) 2 types of fermentation:  Alcoholic fermentation  Lactic acid fermentation ALCOHOLIC FERMENTATION Going from pyruvate to ethanol is a two-step process. 2 molecules CO2 is removed from pyruvate and released thus producing 2 molecules acetaldehyde. NADH passes its electrons to acetaldehyde, regenerating NAD+ and forming 2 molecules ethanol. LACTIC ACID FERMENTATION Lactic acid fermentation converts the pyruvate to the lactic acid (C3H6O3) NADH donates its extra electrons to the pyruvate molecules, regenerating NAD +. https://fatty15.com/blogs/news/cellular-respiration