BIOMOLECULES AND ENZYMES

Detailed explanation-1: -In the final stage of leaf development, cytokinins maintain chlorophyll synthesis while slowing the process of leaf senescence. Thus, cytokinins play an important role during the entire process of leaf development.

Detailed explanation-2: -This suggests that cytokinin may delay leaf senescence not only as a result of exogenous treatment, but as part of an endogenous developmental program.

Detailed explanation-3: -Cytokinin production slows down the process of senescence. However, accumulation of sugars during senescence, due to the breakdown of accumulated starch or the preferential export of N2 from the leaf, can block the effect of cytokinin, especially in low light.

Detailed explanation-4: -Cytokinins especially help in delaying senescence.

Detailed explanation-5: -So, the correct answer is ‘Cytokinins’.