Which of the following hormonal responses to drought stress are correct?

Select 2 answers.

Question

Which of the following hormonal responses to drought stress are correct?

Select 2 answers.

BlackTom AI · Accepted Answer

Question restated: Which of the following hormonal responses to drought stress are correct? Select 2 answers.

Option A: Abscisic acid promotes leaf abscission, decreasing transpiration.
- This is not characteristic of abscisic acid (ABA) under drought. ABA is primarily involved in signaling to close stomata and promote protective gene expression, not triggering leaf abscission as a primary drought response. Leaf abscission is more commonly associated with other hormones like ethylene and auxin balance in developmental or stress contexts, not the central drought response role of ABA. Therefore, this option is not correct.

Option B: Abscisic acid promotes stomata closure, decreasing transpiration.
- This aligns well with the classic drought response role of ABA. Under water deficit, ABA accumulates in guard cells, leading to stomatal closure, which reduces water loss through transpiration. The mechanism involves ABA-induced signaling that activates anion channels, depolarizes the membrane, and causes guard cell turgor loss, closing the stomata. This statement accurately describes ABA’s protective function during drought, making it correct.

Option C: Ethylene promotes stem elongation to improve translocation.
- Ethylene is usually associated with responses such as fruit ripening, leaf abscission, and senescence, rather than promoting stem elongation for drought adaptation. In many contexts, ethylene can suppress growth or accelerate senescence under stress rather than improve translocation. Hence, this claim does not reflect the common drought-response role of ethylene and is not correct in this context.

Option D: Ethylene accelerates senescence of some organs and change allocation of assimilates to stronger sinks.
- This statement captures a known role of ethylene under certain stress conditions, where it can promote senescence and reallocation of resources away from aging tissues toward developing sinks or stressed tissues. While it describes ethylene’s action, it does not describe the ABA-mediated drought response highlighted in the question. Because the question asks for drought-related hormonal responses, this option is not the most direct or primary mechanism for drought response, though it is a true ethylene effect in some contexts. As such, it is not the correct drought-specific response being sought here.

Option E: Abscisic acid promotes expression of proteins that increase desiccation tolerance.
- ABA can induce the expression of stress-responsive proteins and protective proteins (such as late embryogenesis abundant proteins and other desiccation-tolerance–associated genes). This helps cells cope with water deficit and contributes to drought tolerance by protecting cellular structures and functions. This description matches a valid ABA-mediated protective response to drought stress, so this option is correct.

Summary of reasoning for each option:
- A is incorrect because leaf abscission is not the primary ABA-driven drought response; ABA’s main drought role is stomatal closure and gene/protein induction rather than abscission.
- B is correct as ABA’s well-established function during drought is stomatal closure to reduce water loss.
- C is incorrect since ethylene is not typically invoked to promote stem elongation for improved translocation under drought; its drought-related roles more often involve senescence and growth alteration, not enhanced translocation.
- D is contextually true for ethylene’s role in senescence and resource reallocation, but it does not describe the specific ABA-driven drought response asked about in the question, so it is not the correct drought-specific response here.
- E is correct because ABA upregulates proteins that help desiccate stress tolerance, supporting cellular protection under drought.

In terms of the drought-response framework, options B and E directly reflect ABA’s central actions, while A, C, and D describe other hormones or processes that are not the primary ABA-mediated drought responses asked for in this question.

AGRI20026_2025_SM1 Exam: Plant Growth Processes (AGRI20026_2025_SM1)- Requires Respondus LockDown Browser

Which of the following hormonal responses to drought stress are correct? Select 2 answers.

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