Physiological Processes in Crop Production
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Questions and Answers

What is the primary product of photosynthesis in plants?

  • Chlorophyll
  • Carbon dioxide
  • Oxygen
  • Glucose (correct)

    • Which of the following is necessary for the process of photosynthesis to occur?

  • Sunlight (correct)
  • Ethylene
  • Oxygen
  • Nitrogen

    • What characterizes oxygenic photosynthesis?

  • Occurs only in anaerobic organisms
  • Uses carbon dioxide and glucose as reactants
  • Does not require water
  • Involves chlorophyll and produces oxygen (correct)

    • Why is photosynthesis considered crucial for life on Earth?

    <p>It forms the basis of food chains</p> Signup and view all the answers

    What do autotrophs produce through photosynthesis?

    <p>Glucose and oxygen</p> Signup and view all the answers

    Which of the following organisms can directly utilize solar energy to synthesize food?

    <p>Algae</p> Signup and view all the answers

    What is produced as a byproduct of aerobic photosynthesis?

    <p>Oxygen</p> Signup and view all the answers

    In what way do plants store the energy generated from photosynthesis?

    <p>As glucose</p> Signup and view all the answers

    What is the primary role of chlorophyll a in photosystems?

    <p>To act as a reaction center</p> Signup and view all the answers

    Which pigment primarily absorbs light at the wavelength of 680 nm?

    <p>Chlorophyll a (P680)</p> Signup and view all the answers

    What are accessory pigments responsible for in photosynthesis?

    <p>Harvesting additional light energy</p> Signup and view all the answers

    What percentage of absorbed light is actually used by plants during photosynthesis?

    <p>4%</p> Signup and view all the answers

    Where do the light reactions of photosynthesis primarily occur?

    <p>In the thylakoid membranes</p> Signup and view all the answers

    Which of the following is a primary electron acceptor in photosystem I?

    <p>Iron protein (Fe-S)</p> Signup and view all the answers

    What is the role of photosystems in photosynthesis?

    <p>To trap solar energy and convert it into chemical energy</p> Signup and view all the answers

    Which accessory pigment absorbs light energy but does not participate in the main energy conversion process?

    <p>Carotene</p> Signup and view all the answers

    What is the main purpose of the light reactions in photosynthesis?

    <p>To generate ATP and NADPH</p> Signup and view all the answers

    Which wavelengths of light do chlorophyll pigments absorb most efficiently?

    <p>Red and blue wavelengths</p> Signup and view all the answers

    What happens to water during the light reactions?

    <p>It is split to release electrons and hydrogen ions</p> Signup and view all the answers

    What is NADP+ reduced to during the light reactions?

    <p>NADPH</p> Signup and view all the answers

    What role do hydrogen ions play in the generation of ATP during the light reactions?

    <p>They create a positive gradient for ATP synthesis</p> Signup and view all the answers

    Which enzyme is involved in the synthesis of ATP during the light reactions?

    <p>ATP synthetase</p> Signup and view all the answers

    What happens to the oxygen produced during the light reactions?

    <p>It is released as a waste product</p> Signup and view all the answers

    What is the primary role of chloroplasts in plant cells?

    <p>Conduct photosynthesis to produce sugars and oxygen</p> Signup and view all the answers

    What are the end products of the light reactions that are essential for the dark reactions?

    <p>ATP and NADPH</p> Signup and view all the answers

    Why are stomata primarily located on the underside of leaves?

    <p>To reduce water loss due to evaporation</p> Signup and view all the answers

    Which type of chlorophyll is found in all autotrophic organisms except for photosynthetic bacteria?

    <p>Chlorophyll a</p> Signup and view all the answers

    What function do carotenoids serve in relation to chlorophyll?

    <p>They absorb light not utilized by chlorophyll and transfer energy to it</p> Signup and view all the answers

    What is the primary role of ATP and NADPH in the dark reaction of photosynthesis?

    <p>They are used to fix carbon dioxide into carbohydrates.</p> Signup and view all the answers

    What pigment is primarily responsible for the green color of leaves?

    <p>Chlorophyll</p> Signup and view all the answers

    Which enzyme is crucial for the fixation of CO2 in the Calvin Benson Cycle?

    <p>RUBP carboxylase</p> Signup and view all the answers

    What is the first stable product formed during the Calvin Benson Cycle?

    <p>3-PGA</p> Signup and view all the answers

    What part of the leaf is primarily involved in gas exchange?

    <p>Stomates</p> Signup and view all the answers

    Which of the following best describes the structure of chlorophyll?

    <p>Four pyrrole nuclei joined by carbon linkages and magnesium at the center</p> Signup and view all the answers

    Which pathway produces 4-carbon oxaloacetic acid as its first product?

    <p>C4 or Hatch-Slack Pathway</p> Signup and view all the answers

    Which light wavelengths does chlorophyll absorb most effectively?

    <p>Violet-blue and red light</p> Signup and view all the answers

    What is a characteristic feature of CAM plants?

    <p>They close their stomates during the night.</p> Signup and view all the answers

    What internal factor directly affects the rate of photosynthesis?

    <p>Chlorophyll content</p> Signup and view all the answers

    How many molecules of ATP are required to fix one molecule of CO2 in the Calvin Benson Cycle?

    <p>Three molecules of ATP</p> Signup and view all the answers

    What is a critical factor affecting the photosynthesis rate as leaves age?

    <p>Decline in chloroplast functions as leaves age</p> Signup and view all the answers

    Which of the following is a factor that can directly impact the rate of photosynthesis?

    <p>Light intensity</p> Signup and view all the answers

    What effect does increasing temperature have on the rate of photosynthesis between 5°C and 35°C?

    <p>It doubles the rate for every 10°C increase</p> Signup and view all the answers

    Which factor becomes a limiting factor for photosynthesis due to its low concentration in the atmosphere?

    <p>Carbon dioxide</p> Signup and view all the answers

    How does water indirectly affect the rate of photosynthesis?

    <p>By causing stomata to close when in deficit</p> Signup and view all the answers

    Which internal factor is associated with the demand for photosynthate in plants?

    <p>The growth stage of the plant</p> Signup and view all the answers

    What is the effect of very high temperatures on photosynthesis?

    <p>Denatures the enzymes involved in the process</p> Signup and view all the answers

    Which mineral elements are crucial for the functioning of photosynthetic enzymes?

    <p>Magnesium and copper</p> Signup and view all the answers

    What is the primary role of stomata in the context of photosynthesis?

    <p>Facilitating gas exchange, including CO2 uptake</p> Signup and view all the answers

    Study Notes

    Physiological Processes Affecting Crop Production

    • Crop growth and development depend on the interaction of various physiological processes
    • Key processes include photosynthesis, respiration, transpiration, and translocation
    • These processes are fundamental to crop yield

    Photosynthesis - A Chemical Reaction

    • Photosynthesis is an autotrophic process, meaning plants and plant-like organisms (algae) use sunlight to create energy (glucose)
    • The produced glucose is stored as carbohydrate within these organisms
    • Photosynthesis is considered the most important biological process because it provides organic molecules from inorganic materials like carbon dioxide and water
    • It supports all food chains and webs, and produces oxygen

    Photosynthesis Requirements

    • Plants require water, carbon dioxide, light, and chlorophyll for photosynthesis

    Photo-synthesis Definition

    • Photosynthesis is the process of "putting together with light"
    • It converts water and carbon dioxide into glucose (a sugar) using sunlight
    • Plants use glucose for energy and as a building block for growth
    • Autotrophs produce glucose; heterotrophs consume it.

    Two Types of Photosynthesis

    • Anoxygenic photosynthesis is used by obligate anaerobes, capturing light energy to make ATP without oxygen production. Water is not used as an electron source.
    • Oxygenic photosynthesis is the common form in plants, algae, and cyanobacteria. Water is the initial electron donor, resulting in molecular oxygen as a byproduct.

    Photosynthesis Equation

    • 6CO2 + 6H2O + energy → C6H12O6 + 6O2 (carbon dioxide + water + energy → glucose + oxygen)

    Significance of Photosynthesis

    • Green plants contain chlorophyll, capturing, converting, transferring, and storing energy for all life on Earth.
    • Photosynthesis is the process of converting light energy into chemical energy.
    • Other organisms rely on green plants for food production and survival.

    The Photosynthetic Organ - Leaf

    • The leaf is the primary site of photosynthesis.
    • Leaf structure includes upper and lower epidermis (with stomates), mesophyll cells (containing chlorophyll), and vascular bundles (for transport)
    • Mesophyll is further divided into palisade parenchyma (upper layer with regular cells) and spongy parenchyma (lower layer with irregular cells)

    Stomata

    • Stomata are openings on the leaf's underside that allow gas exchange.

    Chloroplasts

    • Chloroplasts are tiny green structures within leaf cells where photosynthesis happens
    • These structures are clearly visible under a high magnification microscope.

    Chloroplasts and Sugars/Oxygen

    • Chloroplasts produce sugars (glucose).
    • Chloroplasts also produce oxygen.

    Photosynthesis Stage 2

    • Captured light energy from Stage 1 is used to produce sugars and oxygen from water
    • Sugars produced are used by the plant cells for energy
    • Oxygen is released through the stomata on the leaf's underside
    • Glucose provides energy for producing other plant materials, such as wax and proteins

    Leaves and Chlorophyll

    • Leaves are green due to the pigment chlorophyll, which absorbs light.
    • Leaves have a large surface area for maximum light absorption.

    Photosynthetic Pigments

    • The photosynthetic pigments include carotenoids, which absorb light in regions of the spectrum not absorbed by chlorophyll, and chlorophyll, the principal pigment in photosynthesis
    • Chlorophyll absorbs light maximally in the violet-blue and red parts of the spectrum; it reflects green light (hence the green color of leaves)

    Visible Light and Electromagnetic Spectrum

    • Visible light is a small part of the electromagnetic spectrum, which encompasses all forms of light

    Chlorophyll Details

    • Chlorophyll is located at the partition between adjacent thylakoids
    • Its basic unit is a porphyrin ring system composed of four pyrrole nuclei linked by carbon linkages
    • The porphyrin center contains a single magnesium atom.

    Kinds of Chlorophyll

    • Chlorophyll a (bluish green) is found in most autotrophic organisms besides photosynthetic bacteria.
    • Chlorophyll b (yellowish green)

    Light Absorption

    • Leaves generally absorb around 83% of light, reflecting 12% and transmitting 5%
    • Only about 4% of absorbed light is used in photosynthesis; the rest is lost as heat.

    Photochemical and Biosynthetic Phase

    • Photosynthesis takes place in chloroplasts.
    • Photosynthesis involves light reactions and dark reactions.
    • Light reactions take place in the grana of the chloroplasts (where chlorophyll is located). Dark reactions take place in the stroma of the chloroplasts (where chlorophyll is not found).

    Light Reaction Details

    • The light reaction of light-dependent reactions happen in the chloroplast's mesophyll cells of the leaves.
    • The primary purpose of the light reaction is to create ATP and NADPH compounds for subsequent dark reactions.

    Light Reaction Steps

    • Chlorophyll absorbs red and blue light most efficiently for photosynthesis.
    • Light absorption excites electrons in chlorophyll.
    • This process happens within photosystems (PSI and PSII).
    • Chlorophyll releases energized electrons, which are replaced by water splitting. This releases hydrogen ions and oxygen.
    • Electrons reach a reaction center where they combine with NADP+ to form NADPH.
    • The built-up hydrogen ions create energy enabling ATP formation.

    Light Reaction Steps - Continued

    • Oxygen is released as a byproduct.
    • Electrons move along a transport chain losing energy
    • Electron transport chain energy used to produce ATP

    Light Reaction End Products

    • ATP and NADPH are the end products of light reactions, used to fix CO2 in the dark reaction

    Synthesis of ATP

    • Light-induced phosphorylation (adding a phosphate group to ADP) produces ATP. This is called photophosphorylation (with non-cyclic and cyclic options).

    Dark Reaction Details

    • Dark reactions occur in the stroma of the chloroplasts.
    • Dark reactions are how inorganic carbon gets converted to carbon.
    • Carbon dioxide reduction and the formation of carbohydrates are part of the dark reaction.
    • Carbon fixation occurs via three pathways:

    Dark Reaction Pathways

    1. Calvin Benson Cycle - fixation/reduction of carbon dioxide (requires 3 ATP and 2 NADPH); takes place in the chloroplast's mesophyll cell; utilizes RUBP (CO2 acceptor) and RUBP Carboxylase enzyme; 3-PGA is the first stable product.

    2. C4 or Hatch Slack Pathway - the first product is 4-carbon oxaloacetic acid (utilizing PEPC enzyme for CO2 fixation and decarboxylation in bundle sheath cells); occurs with Kranz anatomy.

    3. CAM or Crassulacean Acid Metabolism Pathway - stomata close during the day and open during the night to reduce water loss and collect CO2; CO2 is stored as malate, then reacts with RuBisco to produce sugar

    Factors Affecting Photosynthesis

    • Internal factors include chlorophyll amount, leaf age/anatomy, and demand for photosynthetic products
    • External factors include temperature, light, carbon dioxide, water, and mineral elements. Environmental factors affect photosynthesis indirectly by impacting internal processes.

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    Description

    Explore the essential physiological processes that influence crop growth and yield, focusing on key factors such as photosynthesis, respiration, and transpiration. This quiz delves into how these processes interact to determine overall plant health and productivity.

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