The diagram below shows the short-term and long-term responses of a plant to dehydration. Abscisic acid (ABA) is a plant hormone released in response to dehydration. ABA circulates throughout the plant, inducing varying changes in gene expression in different parts of the plant. Which of the following results would you expect to be induced during a long-term drought? Long-term responses Short-term responses Low humidity High temperature High light •Shoot growth inhibition •Reduced transpiration area •Gene responses •Metabolic acclimation •Osmotic adjustment •Root signal recognition •Stomatal closure •Decreased C assimilation •Multi-stress sensing •Gene responses •Root signal recognition •Gene responses •Inhibition of growth •Turgor maintenance •Sustained root growth •Increased root / shoot •Increased absorption area Water deficit Soil compaction •Gene responses •Assimilate transport •Xylem hydraulic changes •Cell drought signalling •Gene responses •Osmotic adjustment A. Accelerated CO2 uptake by leaves and increased transpiration rate B. Increased shoot and leaf growth and increased photosynthesis C. Reduced photosynthesis and increased root growth D. Decreased water uptake activity in roots and a shutdown of CO2 uptake by leaves
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- The question asks about the long-term responses of a plant to dehydration. - The diagram shows both short-term and long-term responses to dehydration. - Abscisic acid (ABA) is mentioned as a hormone that induces changes in gene expression in response to Show more…
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The water lost during transpiration is a negative side effect of the plant's requirement for gas exchange. Which of the following is a positive effect of this water loss? a. increased mineral transport and increased growth b. evaporative cooling and increased turgor c. increased turgor and increased growth d. evaporative cooling and increased mineral transport
Shaiju T.
The Transpiration Tension Cohesion mechanism explains how water is moved through the plant from the roots to the leaf tissue. Which below is incorrect in regards to this mechanism? Select one: a. The removal of water from the xylem 'veins' in turn establishes tension on the entire column of water contained in the xylem (through the veins, through the shoot, to the root). b. The leaves, through the process of transpiration, lose water that surrounds the mesophyll cells in the apoplastic space to outside of the leaf. This reduction of water surrounding each cell (in the cell wall) increases the negative pressure potential (Psi P) creating negative tension. c. All of the statements are true and explain the mechanism. d. Due to the polar nature of water, which allows for hydrogen bonding between these molecules (resulting in cohesion), the water column is maintained (no breakage). Thus, as leaves transpire they create negative tension that draws water into them. This negative potential in turn draws water up the xylem to replace the respired water. e. The negative tension created by the mesophyll cells is greater than that of the xylem, the water-conducting vascular tissue. This explains how leaves stay hydrated (and replaces the water lost due to transpiration).
Adi S.
Plants lose water from their aboveground surfaces in the process of transpiration. Most of this water is lost from stomata. Excess loss of water has severe consequences and may be fatal for the plant. The table shows data collected on a sunny day. What is the best explanation for the transpiration rates leveling off and declining at temperature higher than $27^{\circ} \mathrm{C} ?$ a. The plant ran out of water. b. The plant needs less water as temperature increases, so transpiration slows down to limit water uptake by the roots. c. Stomata close to conserve water, slowing down transpiration. d. The amount of water in the leaves decreases at high temperature and less is available for evaporation.
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