Question

Which combinations of the following statements about Abscisic Acid (ABA) in plants are correct?
• [(A).] ABA is important for plant development and desiccation tolerance. 
• [(B).] ABA influences the expression of various genes, including the gene for Late Embryogenesis Abundant (LEA) proteins. 
• [(C).] ABA also regulates the closure of aquaporins. 
• [(D).] Like GAs, the ABA also strongly promotes early flowering in plants. 
Choose the correct answer from the options given below: 
 

• A. (A), (B) and (C) only.
• B. (A), (B) and (D) only.
• C. (A), (C) and (D) only.
• D. (B), (C) and (D) only.

Hint:

To remember the functions of ABA, associate it with the "Stress and Seed" hormone:
- It regulates stomatal closure and protects cells during drought stress.
- It maintains seed dormancy and prevents vivipary (premature germination on the parent plant).

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Abscisic Acid (ABA) is a major phytohormone that primarily functions as a growth inhibitor and mediator of plant stress responses, particularly during drought, salinity, and cold stress.

Step 3: Detailed Explanation:
Let us evaluate each of the statements:
- Statement (A) is correct: ABA is a critical regulator of seed development, maturation, and dormancy.
It protects embryonic tissue from drying out by promoting desiccation tolerance before the seed enters dormancy.
- Statement (B) is correct: Under water stress and during seed maturation, ABA stimulates the transcription of genes encoding Late Embryogenesis Abundant (LEA) proteins.
LEA proteins act as molecular chaperones, protecting cellular proteins and membranes from denaturation during dehydration.
- Statement (C) is correct: ABA regulates plant water balance by controlling stomatal closure and modifying the activity and gating of aquaporins (water channel proteins) to optimize water transport during stress.
- Statement (D) is incorrect: Gibberellins (GAs) promote flowering (particularly in long-day and rosette plants).
In contrast, ABA generally acts as a growth retardant and delays flowering under normal conditions.
Therefore, statements (A), (B), and (C) are correct, while (D) is incorrect.

Step 4: Final Answer:
The correct combination is (A), (B) and (C) only, matching Option (A).