B-Nine is a commercially used chemical that shortens or dwarfs plants.

B-Nine is a commercially used chemical that shortens or dwarfs plants.

• A. Ethylene
• B. Paclobutrazol
• C. B-Nine
• D. Gibberellic acid

Answer: (C)

Plant height is governed by gibberellins, hormones that promote stem elongation. When GA production is reduced, cells don’t elongate as much, so stems stay short and the plant becomes more compact. B-Nine is paclobutrazol, a growth regulator that blocks a step in gibberellin biosynthesis. With less GA available, internodes shorten and the plant dwarfs, which is exactly the effect described. That’s why B-Nine best fits the description. Ethylene mainly governs ripening and stress responses rather than producing a controlled dwarfing effect. Gibberellic acid, on the other hand, stimulates elongation, making plants taller rather than shorter.

Plant height is governed by gibberellins, hormones that promote stem elongation. When GA production is reduced, cells don’t elongate as much, so stems stay short and the plant becomes more compact. B-Nine is paclobutrazol, a growth regulator that blocks a step in gibberellin biosynthesis. With less GA available, internodes shorten and the plant dwarfs, which is exactly the effect described. That’s why B-Nine best fits the description.

Ethylene mainly governs ripening and stress responses rather than producing a controlled dwarfing effect. Gibberellic acid, on the other hand, stimulates elongation, making plants taller rather than shorter.