NEET Biology question

A young dicot seedling (e.g. soybean) is laid horizontally on a surface and is subjected to the gravity stimulus. The shoot bends in the upward direction and the root bends in the downward direction. Which of the following is the possible reason for this movement?

(A)Redistribution of auxins throughout the seedling is responsible for the stimulatory unequal growth in shoots and roots
(B)Redistribution of cytokinins throughout the seedling is responsible for the stimulatory unequal growth in roots and shoots
(C)Redistribution of auxins in roots and cytokinins in shoots is responsible for stimulatory unequal growth
(D)Redistribution of auxins in shoots and cytokinins in roots is responsible for stimulatory unequal growthCorrect

Answer: (D)

Solution

Gravitropic bending results from an asymmetric (lateral) redistribution of auxin under gravity: in the horizontally placed shoot, auxin accumulates on the lower side, stimulating greater elongation there and causing the shoot to bend upward (negative gravitropism); in the root, the same lateral auxin accumulation on

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Question ID VK-114513