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Plant Hormones and Responses Quiz
61 Questions
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Plant Hormones and Responses Quiz

Created by
@MesmerizingBongos

Questions and Answers

Which of the following has the best chance of creating iris blooms in winter?

  • Alternate four hours of darkness with four hours of light repeatedly over each 24-hour period.
  • Artificially increase the period of darkness in the greenhouse.
  • Increase the temperature to more closely follow summer temperatures.
  • Interrupt the long winter nights with a brief period of light. (correct)

    • Which reason best describes the loss of fitness in the individual plant that could not grow towards light?

  • The plant could not adjust to directional light, which reduced photosynthetic activity and therefore energy available for reproduction. (correct)
  • The plant was too short to attract insects for pollination.
  • Because the plant grew much taller and straighter, resources that could be used for reproduction were used for growth.
  • The loss of a phototropic response meant that the plant's seeds could not germinate, so reproduction would be unsuccessful.

    • The hormone that helps plants respond to drought is?

  • Ethylene
  • Auxin
  • Cytokinin
  • Abscisic acid (correct)

    • Auxin enhances cell elongation in all of these ways except?

    <p>Acid-induced denaturation of cell wall proteins.</p> Signup and view all the answers

    Charles and Francis Darwin discovered that?

    <p>Auxin is responsible for phototropic curvature.</p> Signup and view all the answers

    How may a plant respond to severe heat stress?

    <p>By producing heat-shock proteins, which may protect the plant's proteins from denaturing.</p> Signup and view all the answers

    The signaling molecule for flowering might be released earlier than usual in a long-day plant exposed to flashes of?

    <p>Red light followed by far-red light during the night.</p> Signup and view all the answers

    If a long-day plant has a critical night length of 9 hours, which 24-hour cycle would prevent flowering?

    <p>8 hours light/8 hours dark/light flash/8 hours dark</p> Signup and view all the answers

    A plant mutant that shows normal gravitropic bending but does not store starch in its plastids would require a reevaluation of the role of ________ in gravitropism.

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

    The detector of light during de-etiolation (greening) of a tomato plant is (are) ________.

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

    Plant hormones ________.

    <p>Affect only cells with the appropriate receptor</p> Signup and view all the answers

    Which of the following mechanisms is the correct sequence of events that takes place during the plant responses to internal and external signals?

    <p>Reception, transduction, and response</p> Signup and view all the answers

    Which of the following mechanisms is in the correct sequence of steps that takes place during the formation of de-etiolation response proteins in plants?

    <p>I, II, III, and IV</p> Signup and view all the answers

    Which of the following can function in signal transduction in plants?

    <p>Only I, III, and V</p> Signup and view all the answers

    Plant hormones produce their effects by ________.

    <p>Only I and II</p> Signup and view all the answers

    Plant hormonal regulation differs from animal hormonal regulation in that ________.

    <p>There are no dedicated hormone-producing organs in plants as there are in animals</p> Signup and view all the answers

    Auxins in plants are known to affect which of the following processes?

    <p>Only I, III, IV, and V</p> Signup and view all the answers

    Experiments on the positive phototropic response of plants indicate that ________.

    <p>Auxin can move to the shady side of the stem</p> Signup and view all the answers

    What are the primary sites of auxin (IAA) production in plants?

    <p>Shoot apical meristem and young leaves</p> Signup and view all the answers

    What are the primary sites of ethylene production in high concentrations in plants?

    <p>Ripening fruits</p> Signup and view all the answers

    Which one of the following hormones regulates cell division in plants?

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

    Which one of the following hormones stimulates stem elongation and pollen tube growth?

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

    Generally, each hormone has multiple functions in plants depending on ________.

    <p>I, II, III, and IV</p> Signup and view all the answers

    Apical dominance in plants is under the control of ________.

    <p>Various plant hormones</p> Signup and view all the answers

    Arrange the following steps that occur during drought tolerance in plants in a correct sequence.

    <p>I, II, III, and IV</p> Signup and view all the answers

    Which of the following statements best summarizes the acid growth hypothesis in an actively growing shoot?

    <p>Auxin-activated proton pumps lower the pH of the cell wall, which breaks bonds and makes the walls more flexible.</p> Signup and view all the answers

    Which of the following conclusions is supported by the research of both Peter Boysen-Jensen and Charles and Francis Darwin on shoot responses to light?

    <p>A chemical substance involved in shoot bending is produced in shoot tips.</p> Signup and view all the answers

    An eccentric millionaire botanist has offered a $25,000 scholarship to anyone who can successfully get a plant to grow through a vertical maze in complete darkness. Which of the following techniques will help you succeed?

    <p>Apply auxin directly to the part of the stem just below the tip opposite from the direction you want the stem to bend.</p> Signup and view all the answers

    You have a small tree in your yard that is the height that you want it, but does not have as many branches as you want. How can you prune it to trigger it to increase the number of branches?

    <p>Cut off the tips of the main shoots.</p> Signup and view all the answers

    As cytokinins are primarily produced in roots, what route would they travel to influence lateral shoot formation in a recently topped tree?

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

    Who might be interested in using cytokinins?

    <p>Florists, to dip stems in to keep leaves green longer</p> Signup and view all the answers

    If a farmer wanted more loosely packed clusters of grapes, he would most likely spray the immature bunches with ________.

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

    ________ prevents seeds from germinating until conditions are favorable for the growth of the plant.

    <p>Abscisic acid</p> Signup and view all the answers

    A population of plants experiences several years of severe drought. Much of the population dies due to lack of water, but a few individuals survive. You hypothesize that the survivors have the ability to synthesize higher levels of ________ than their siblings do.

    <p>Abscisic acid</p> Signup and view all the answers

    If you were shipping green bananas to a supermarket thousands of miles away, which of the following chemicals would you want to eliminate from the plants' environment?

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

    In the fall, the leaves of some trees change color. This happens because chlorophyll breaks down and the accessory pigments become visible. What hormone is responsible for this?

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

    Which type of mutant would be most likely to produce a bushier phenotype?

    <p>Strigolactone underproducer</p> Signup and view all the answers

    Vines in tropical rain forests must grow toward large trees before being able to grow toward the sun. To reach a large tree, the most useful kind of growth movement for a tropical vine presumably would be ________.

    <p>Negative thigmotropism</p> Signup and view all the answers

    Upon exposure to blue light, plants not only begin to grow toward the light, but move their chloroplasts to the sunny side of each cell. The adaptive advantage of moving chloroplasts to the sunny side of each cell ________.

    <p>Maximizes light absorption by the chloroplasts for photosynthesis</p> Signup and view all the answers

    Mammalian eyes sense light because the photoreceptor cells have molecules called opsins, which change structure when exposed to light. Which of the following plant molecules would be analogous to mammalian opsins in their light-sensing ability?

    <p>Pfr and phytochrome</p> Signup and view all the answers

    Seed packets give a recommended planting depth for the enclosed seeds. The most likely reason some seeds are to be covered with only 1/4 inch of soil is that the ________.

    <p>Seeds require light to germinate</p> Signup and view all the answers

    Suppose a plant had a photosynthetic pigment that absorbed far-red wavelengths of light. In which of the following environments could that plant thrive?

    <p>On the forest floor, beneath a canopy of taller plants</p> Signup and view all the answers

    The biological clock controlling circadian rhythms must ultimately ________.

    <p>Affect gene transcription</p> Signup and view all the answers

    Which of the colors of visible light induces curvature in coleoptiles most effectively?

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

    Phytochrome plays a critical role in seed germination. Which of the colors maximizes seed germination?

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

    Many plants flower in response to day-length cues. Which of the following statements best summarizes this phenomenon?

    <p>Flowering in short-day and long-day plants is controlled by phytochrome.</p> Signup and view all the answers

    Plants often use changes in day length (photoperiod) to trigger events such as dormancy and flowering. It is logical that plants have evolved this mechanism because photoperiod changes ________.

    <p>Are more predictable than air temperature changes</p> Signup and view all the answers

    A gardener in Canada wants to surprise his mother on her birthday and make her favorite hibiscus bush flower in May instead of at the end of June. Which of the following might make the hibiscus bush flower early?

    <p>Exposing flower buds of the hibiscus bush to short nights</p> Signup and view all the answers

    Which of the following environmental factors can be sensed by plants?

    <p>I, II, III, and IV</p> Signup and view all the answers

    Shoots that grow vertically toward the sun can be characterized as ________.

    <p>Positive for phototropism and negative for gravitropism</p> Signup and view all the answers

    Suppose you laid a seedling on its side so that the root was parallel to the ground as shown in the figure. Several hours after the change in position, where in the root cells, position A, B, or C in the figure, would you find the amyloplasts?

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

    The rapid leaf movements resulting from a response to touch (thigmotropism) primarily involve ________.

    <p>Potassium channels</p> Signup and view all the answers

    In extremely cold regions, woody species may survive freezing temperatures by ________.

    <p>Increasing cytoplasmic levels of specific solute concentrations, such as sugars</p> Signup and view all the answers

    Most scientists agree that global warming is underway; thus, it is important to know how plants respond to heat stress. Which of the following would be a useful line of inquiry to try and improve plant response and survival to heat stress?

    <p>Increased production of heat-shock proteins</p> Signup and view all the answers

    When an arborist prunes a limb off a valuable tree, he or she may paint the cut surface. The primary purpose of the paint is to ________.

    <p>Block entry of pathogens through the wound</p> Signup and view all the answers

    You are out working in your garden, and you notice that one of your favorite flowering plants has black, dead spots on the leaves. You immediately suspect that the plant has been invaded by a pathogen and has initiated a(n) ________.

    <p>Hypersensitive response</p> Signup and view all the answers

    Generalized defense responses in organs distant from the infection site are called ________.

    <p>Systemic acquired resistance</p> Signup and view all the answers

    A particular species of virus carries a gene for salicylate hydroxylase, an enzyme that breaks down salicylic acid. Will this virus be more or less virulent to plants than other viruses?

    <p>More virulent</p> Signup and view all the answers

    Which event during the evolution of land plants favored the synthesis of secondary compounds?

    <p>The rise of herbivory</p> Signup and view all the answers

    For a plant to initiate chemical responses to herbivory, before it is directly affected by herbivores, ________.

    <p>Volatile 'signal' compounds must be perceived</p> Signup and view all the answers

    You may have observed plants rotate towards a light source, thereby increasing the plant's ability to intercept light energy and increase photosynthesis. Using your knowledge of phototropism, which of the following experimental procedures would you use to complete your task?

    <p>Cover the growing tip of the grass seedling with black paper.</p> Signup and view all the answers

    Study Notes

    Plant Hormones and Responses

    • Phytochrome is the key light detector during de-etiolation (greening) of tomato plants.
    • Plant hormones are effective only in cells with appropriate receptors.
    • The correct sequence of plant responses to signals includes reception, transduction, and response.

    Mechanisms of Plant Hormones

    • The formation of de-etiolation response proteins follows this sequence: detection of light signal, activation of phytochrome, activation of specific kinases, formation of response proteins.
    • Calcium ions, receptor proteins, and secondary messengers are vital in plant signal transduction.
    • Plant hormones alter gene expression and membrane permeability to produce their effects.

    Functions and Impact of Auxins

    • Auxins play a role in gravitropism, phototropism, inhibition of lateral buds, and apical dominance.
    • Auxin distribution influences the curvature of plants in response to light, moving to the shady side of the stem.
    • The primary sites for auxin (IAA) production are the shoot apical meristem and young leaves.

    Other Plant Hormones

    • Ethylene, primarily produced in ripening fruits, affects various processes including leaf color change in autumn.
    • Cytokinins regulate cell division and are primarily produced in roots, influencing lateral shoot formation.

    Responses to Environmental Factors

    • Plants can sense gravity, pathogens, wind, and light, utilizing this information to adapt and survive.
    • Drought responses in plants involve ABA accumulation leading to stomatal closure and reduced transpiration.

    Phototropism and Growth

    • Blue light is most effective in inducing curvature in coleoptiles; phytochrome maximizes seed germination under red light.
    • Plants utilize photoperiod cues to control flowering and dormancy.

    Defense Mechanisms

    • Plants initiate defense responses to pathogens via localized responses and systemic acquired resistance.
    • Secondary compounds are synthesized in response to herbivory, enhancing plant survival.

    Genetic and Environmental Interactions

    • Plants with mutations that affect phototropism show reduced fitness due to lower photosynthetic activity.
    • Environmental factors like temperature and light duration influence plant growth and flowering.

    Practical Applications

    • Grafting or manipulating exposure to light can alter flowering times in plants, relevant for horticultural practices.
    • Knowledge of plant hormones can aid in enhancing crop resilience to stress conditions like drought and heat.### Auxin and Phototropism
    • Auxin influences phototropic curvature in plants, aiding their growth direction towards light.
    • Red light is proven to be the most effective in facilitating shoot phototropism.
    • Light exposure impacts auxin levels, as light can destroy auxin.
    • Light perception occurs primarily at the tips of coleoptiles, crucial for directional growth.

    Plant Response to Heat Stress

    • Plants can combat severe heat stress by:
      • Reorienting leaves to enhance evaporative cooling and reduce temperature.
      • Developing air tubes to improve ventilation and gas exchange.
      • Producing heat-shock proteins that safeguard plant proteins from denaturing.
      • Increasing unsaturated fatty acids in cell membranes, which helps maintain membrane fluidity.

    Signaling Molecules and Flowering

    • In long-day plants, the release of flowering signaling molecules can be triggered sooner by specific light exposures, such as:
      • Exposure to far-red light at night, which may disrupt normal flowering signals.
      • Red light during the night can also enhance signaling pathways related to flowering.
      • A combination of red followed by far-red light during the night can influence flowering timing.

    Critical Night Length in Long-Day Plants

    • A long-day plant with a critical night length of 9 hours requires specific light and dark cycles to prevent flowering:
      • 16 hours of light paired with 8 hours of darkness does not inhibit flowering.
      • A cycle of 14 hours light and 10 hours dark will prevent flowering effectively.

    Gravitropism and Plant Mutations

    • A mutant plant exhibiting normal gravitropic bending but lacking starch storage in plastids suggests the need for further analysis of statoliths' role in gravitropism.
    • Statoliths are sensory organelles involved in perceiving gravity and directing growth.

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    Description

    Test your understanding of how plant hormones regulate growth and responses to light and gravity. This quiz covers key concepts such as signal transduction, auxin functions, and the role of phytochrome in de-etiolation. Perfect for students studying plant biology or related fields.

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