Plant Responses to the Environment
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Questions and Answers

What do plant hormones help coordinate in plants?

  • Only responses to environmental stimuli
  • Growth, development, and responses to environmental stimuli (correct)
  • Only growth and development
  • Only responses to internal stimuli

    • What is the function of cellular receptors in plants?

  • To respond to environmental changes
  • To initiate signal transduction pathways
  • To regulate gene expression
  • To detect important changes in the environment (correct)

    • What is the name of the receptor responsible for detecting light in plants?

  • Photoreceptor
  • Phytochrome (correct)
  • Light receptor
  • Phytohormone

    • Where is the phytochrome receptor located in plant cells?

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

    What is the outcome of a signal transduction pathway in plants?

    <p>All of the above</p> Signup and view all the answers

    What is the term for the effects of light on plant morphology?

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

    What role does light play in plant growth and development?

    <p>Important for many key events in plant growth and development</p> Signup and view all the answers

    What aspect of light can plants detect?

    <p>Direction, intensity, and wavelengths</p> Signup and view all the answers

    What is the primary factor that triggers flowering in a day-neutral plant?

    <p>Maturity and development of the plant</p> Signup and view all the answers

    What is the critical daylength for a short-day plant to develop flowers?

    <p>Less than 15.5 hours</p> Signup and view all the answers

    Why are the terms 'long-day' and 'short-day' used in plant physiology?

    <p>Because night length is the critical factor, but the terms are historically embedded</p> Signup and view all the answers

    What is the result of interrupting a long night with a flash of red light in a 'night-interruption' experiment?

    <p>Flowering is inhibited</p> Signup and view all the answers

    What is the role of PFR in the biological clock of plants?

    <p>It resets the clock</p> Signup and view all the answers

    What is the effect of a flash of far-red light in a 'night-interruption' experiment?

    <p>No effect is seen</p> Signup and view all the answers

    What is the main function of auxins in plant growth?

    <p>Stimulate cell elongation</p> Signup and view all the answers

    What is the natural auxin found in plants?

    <p>Indole-3-acetic acid (IAA)</p> Signup and view all the answers

    What is the effect of auxins on lateral bud growth?

    <p>Inhibit lateral bud growth</p> Signup and view all the answers

    Where are cytokinins primarily produced in plants?

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

    What is the effect of cytokinins on leaf senescence?

    <p>Delay leaf senescence</p> Signup and view all the answers

    What is the primary function of gibberellins in plants?

    <p>Enhance stem elongation</p> Signup and view all the answers

    How do auxins move through the plant?

    <p>By polar transport through parenchyma cells</p> Signup and view all the answers

    What is the effect of auxins on root growth?

    <p>Stimulate lateral root growth</p> Signup and view all the answers

    What is the primary function of phytochrome in plants?

    <p>To control plant circadian rhythms</p> Signup and view all the answers

    What is the result of PFR absorbing far-red light?

    <p>It becomes PR</p> Signup and view all the answers

    What is the approximate period of the biological clock regulated by phytochrome?

    <p>24 hours</p> Signup and view all the answers

    What is the active form of phytochrome in most plants?

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

    What is the effect of red light on PR?

    <p>It becomes PFR</p> Signup and view all the answers

    What is the structure of phytochrome?

    <p>A protein covalently bonded to a chromophore</p> Signup and view all the answers

    What happens to PFR in the dark?

    <p>It becomes PR</p> Signup and view all the answers

    What is the role of the chromophore in phytochrome?

    <p>It absorbs light</p> Signup and view all the answers

    What is the role of gibberellins in seed germination?

    <p>To stimulate the production of amylase in the aleurone layer</p> Signup and view all the answers

    What is the effect of ethylene on fruit?

    <p>It promotes fruit ripening</p> Signup and view all the answers

    Which hormone promotes leaf abscission?

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

    What is the role of abscisic acid in seeds?

    <p>It regulates seed maturation</p> Signup and view all the answers

    What is the effect of water stress on ethylene production?

    <p>It promotes ethylene production</p> Signup and view all the answers

    What is the role of indole-3-acetic acid (IAA) in relation to ethylene?

    <p>It promotes ethylene production</p> Signup and view all the answers

    What is the effect of storing fruits in a plastic bag on ethylene levels?

    <p>It increases ethylene levels</p> Signup and view all the answers

    What is the effect of treating apples with carbon dioxide on ethylene production?

    <p>It inhibits ethylene production</p> Signup and view all the answers

    Study Notes

    Plant Responses to the Environment

    • Plant hormones help coordinate growth, development, and responses to environmental stimuli
    • Plants have cellular receptors that detect important changes in their environment

    Signal Transduction Pathways

    • Link internal and environmental signals to cellular responses
    • Signals are detected by receptors, which change shape in response to a specific stimulus
    • Receptors initiate a specific series of biochemical steps, leading to the regulation of cellular activities

    Light and Plant Responses

    • Light is important for photosynthesis and key events in plant growth and development
    • Plants detect direction, intensity, and wavelengths of light using phytochrome
    • Phytochrome is a photoreceptor that consists of a protein covalently bonded to a non-protein part that functions as a chromophore
    • Phytochrome occurs in two interchangeable forms: PR and PFR, which respond to red and far-red light respectively

    Photomorphogenesis

    • Light reception is important for photomorphogenesis, which affects plant morphology
    • Phytochrome is involved in resetting the internal biological clock of many plants
    • The biological clock has a period of approximately 24 hours and controls plant circadian rhythms (e.g., leaf movement)

    The Flowering Process

    • Long-day plants develop flowers when the day length is longer than a critical period (e.g., 14 hours)
    • Short-day plants develop flowers when the day is shorter than a critical period (e.g., 15.5 hours)
    • Day-neutral plants develop flowers regardless of day length
    • Phytochrome can reset the biological clock, influencing flowering

    Hormones and Plant Growth

    • Auxins regulate phototropism and gravitropism
    • Auxins promote stem growth, cell elongation, and vascular differentiation
    • Auxins delay leaf abscission and promote lateral root growth
    • Indole-3-acetic acid (IAA) is the natural auxin, derived from tryptophan

    Cytokinins

    • Produced mainly in roots and travels through the xylem
    • Promote cell division and stimulate lateral bud growth
    • Delay leaf senescence or abscission
    • Regulate protein synthesis

    Gibberellins

    • Produced in embryonic tissues, developing seeds and fruits, and root apices
    • Promote stem elongation and enhance the effects of auxin
    • Stimulate germination in buds and seeds
    • Used commercially to break dormancy

    Ethylene

    • Found in all plant tissues and is a gaseous hormone
    • Formed from the amino acid methionine
    • Promotes leaf abscission and fruit ripening
    • Used commercially for fruit ripening

    Abscisic Acid

    • Produced in leaves, stems, and green fruits
    • Causes stomatal closure during water stress
    • Promotes dormancy in seeds and buds
    • Plays an important role in embryogenesis by stimulating starch and protein accumulation
    • Regulates seed maturation and germination through gene expression in direct competition with gibberellins

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    Description

    Learn how plants respond to environmental stimuli, including changes in growth hormones, injuries, and day length, and how they use cellular receptors to detect these changes.

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