Home > Communication: Chemical Signals > Summary Review
A hormone is [Hint]
a small molecule that controls growth or metabolism only at extremely high concentrations. a small molecule that controls growth or metabolism at extremely low concentrations. a secondary metabolite that functions in defense. a molecule that is not transported.
Auxin is water soluble and will diffuse easily into an agar block. Application of auxin can produce a phototropic response even in the dark. Auxin is involved in the phototropic response by promoting cell elongation. Auxin produces the phototropic response by acting as the light receptor.
The Cholodny-Went Hypothesis explaining the phototropic response was supported by Briggs’ experiment using: [Hint]
slivers of agar inserted into corn shoots, dividing them in half. thin sheets of mica, dividing shoot tips completely in half. sheets of plastic inserted laterally in corn roots. agar blocks that blocked light, preventing the photodestruction of auxin.
Which of the following statements provides evidence that ABP1 is the auxin receptor? [Hint]
Recombinant plants containing many copies of the ABP1 gene were unaffected. The ABP1 gene is only found in recombinant plants. Recombinant plants containing many copies of the ABP1 gene developed abnormally large leaf cells. ABP1 was not recognized by radioactively labeled auxin.
Auxin causes the pH of the cell wall to rise from 5.5 to 6.5, leading to a release of water. Auxin triggers the production of many more ABP1 receptors. Auxin is produced in response to cell elongation, rather than inducing it. Auxin triggers the installation of additional proton pumps and the activation of expansion proteins.
Apical dominance is defined as the [Hint]
mode of leaf growth where the leaf tip is significantly smaller than the leaf base. mode of stem growth where the topmost meristem dominates and destroys the lower meristems. mode of stem growth where the topmost meristem dominates and forces the lower meristems to expand. mode of stem growth where the topmost meristem inhibits the growth of meristems lower down.
gibberellin cytokinin auxin abscisic acid
Considering the chemiosmotic model of auxin transport, what arrangement of auxin transporters would you hypothesize in a typical root cell? [Hint]
influx and efflux carriers distributed equally around the cell Only efflux carriers are present in root cells. influx carriers at the cell base, efflux carriers at the cell top influx carriers at the cell top, efflux carriers at the cell base
Changes in auxin concentration signal tissues to react to changes in the plant’s environment. Auxin attracts deer that eat the shoot apices and modify plant growth and overall shape. Auxin is the major determinant of leaf senescence and abscission. As the sole regulator of plant growth, auxin alone produces the overall shape of the plant.
GA and ABA both stimulate plant growth. GA stimulates plant growth, and ABA inhibits plant growth. ABA synthesis destroys existing pools of GA, thereby stimulating plant growth. metabolic intermediates between GA and ABA actually stimulate plant growth.
Production of the enzyme alpha-amylase is an important step in the germination of barley seeds. Why? [Hint]
The enzyme breaks down starches in the seed coat, thereby allowing the radicle to emerge. The enzyme catalyzes the breakdown of starch to sugar. The enzyme acts as a signal that photosynthesis has begun. The enzyme causes the synthesis of starch from free sugar molecules.
How does gibberellic acid (GA) stimulate production of α-amylase? [Hint]
GA detects the presence of light, signaling appropriate conditions for germination. GA inhibits the production of the Myb protein. GA causes the aleurone cells to elongate into the endosperm and increase the concentration of α-amylase. GA promotes the production of Myb, which acts as a transcription activator.
Japan, using rice plants infected with a plant pathogenic fungus. England, using reed canary grass treated with GA. Japan, using barley plants that carried a recessive GA-sensitive mutation. America, using rice plants artificially treated with gibberellins.
controls production of the enzyme responsible for increased yield in peas. controls production of the enzyme responsible for conversion of the active form of ABA. controls production of the auxin-binding protein, ABP. controls production of the enzyme responsible for conversion of the active form of GA.
The target cell’s response often occurs because specific genes are turned on or off. Hormones initiate a chain of events by interacting directly with the plant’s DNA. Different hormones interact because they induce different transcription activators and repressors. Hormones initiate a chain of events by interacting directly with a receptor molecule.
By what mechanism do roots communicate water status to leaves? [Hint]
ABA produced in roots with adequate water is transported to the leaves, causing stomata in the leaves to open. Fewer potassium ions are taken up by the roots, so fewer are transported to the leaves. This causes stomata to open so more water can be acquired. ABA produced in water-stressed roots is transported to the leaves, causing stomata in the leaves to close. GA produced in water-stressed roots is transported to the leaves, causing stomata in the leaves to close.
They are structurally related to certain animal hormones. Their effect can be reproduced by adding extracts of fungal cultures. They inhibit plant growth. They cause closure of stomata in response to water stress.
They interact with mRNA and turn DNA replication on or off. They interact with DNA and turn transcription on or off. They interact directly with hormones and limit transcription. They synthesize hormones that interact with DNA and turn transcription on or off.
volatile agents in the plastic. The ripe banana had nothing to do with accelerated ripening. the increased metabolic rate of the ripe banana raised the temperature in the bag and accelerated fruit ripening. the ripe fruit (being more advanced) used up the oxygen in the bag and created an environment with high CO2 concentration. the ripe fruit gave off ethylene, which was contained in the bag and accelerated fruit ripening.
a broad-spectrum herbicide containing glyphosate. a selective herbicide containing a natural auxin. a selective herbicide containing a synthetic auxin. a selective herbicide containing the natural hormone ethylene.
