Gibberellins: Plant Growth Promoters — NEET Biology
✅ Asked in NEET 2025Which plant hormone causes cell elongation, especially in stems? [Neet 2025]
Which plant hormone causes cell elongation, especially in stems? [Neet 2025]
Answer & NCERT explanation
Correct answer: A — Gibberellins
Gibberellins are the primary plant hormones responsible for cell elongation, particularly in stem internodes. They promote cell division and elongation by increasing cell wall plasticity and enhancing DNA synthesis. This leads to dramatic increases in stem height. Ethylene causes fruit ripening, cytokinins promote cell division, and abscisic acid is an inhibitory hormone that causes stomatal closure and dormancy.
Read more NCERT concept on the PYQ
Gibberellins are another kind of promotory PGR. There are more than 100 gibberellins reported from widely different organisms such as fungi and higher plants. They are denoted as GA₁, GA₂, GA₃ and so on. However, Gibberellic acid (GA₃) was one of the first gibberellins to be discovered and remains the most intensively studied form. All GAs are acidic. They produce a wide range of physiological responses in the plants. Their ability to cause an increase in length of axis is used to increase the length of grapes stalks. Gibberellins, cause fruits like apple to elongate and improve its shape. They also delay senescence. Thus, the fruits can be left on the tree longer so as to extend the market period. GA₃ is used to speed up the malting process in brewing industry.
NTA tests gibberellins because they are key plant growth regulators that increase axis length and have practical agricultural applications. Students often confuse gibberellins with auxins or think they only affect flowering—but the NCERT explicitly states gibberellins cause axis elongation, fruit development, and delay senescence. The trap is memorizing individual GA types (GA₁, GA₂, GA₃) without understanding their function. Remember: gibberellins are acidic hormones that promote cell elongation and are used commercially in grape stalks and brewing. Focus on their physiological effects: elongation, fruit improvement, and senescence delay—these are testable concepts.
What does NCERT say about Gibberellins are another kind?
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