Directions : In the following question more than one of the answers given may be correct. Select the correct answer and mark it according to the code:
Consider the following statements- (1) Negative geotropism in horizontal stems is caused by accumulation of auxins on the lower side (2) Pineapple can be made to flower in off season by the application of ethylene (3) The ratio of auxin to cytokinin controls cell differentiation (4) Large sized grapes can be produced through cytokinin treatmentA) 1, 2 and 3 are correct
B) 1 and 2 are correct
C) 2 and 4 are correct
D) 1 and 3 are correct
Correct Answer: A
Solution :
In a plant organ, auxins are collected in the opposite side of light. In horizontal stems, auxins are accumulated on the lower side due to which it grows upwards (towards light) hence, shows negative geotropism. Ethylene stimulates flowering in pineapple and related plants while in other cases, it causes fading of flowers and sleep disease (inrolling of petals in blossomed flowers). Cytokinins are the plant hormones that in combination with auxin stimulate cell division and alongwith a number of other factors, determine the source of differentiation. High auxin to cytokinin ratio favours root development, high cytokinin to auxin ratio favours shoot development while intermediate concentration results in the formation of undifferentiated cells. Parthenocarpy is induced by gibberellins. Seedless and fleshy tomatoes and large sized grapes are produced by gibberellin treatment on commercial scale.
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