BIOMOLECULES AND ENZYMES

Detailed explanation-1: -Cytokinins (CK) are a class of plant hormones that promote cell division, or cytokinesis, in plant roots and shoots. They are involved primarily in cell growth and differentiation, but also affect apical dominance, axillary bud growth, and leaf senescence.

Detailed explanation-2: -Cytokinin promotes nuclear localization of a transcription factor to activate cell division. Organ morphogenesis in plants is largely determined by the rate and patterns of cell division (1) occurring primarily in meristematic tissues such as the shoot and root meristems, and vascular cambium (2).

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 promote cell division and increase cell expansion during the proliferation and expansion stages of leaf cell development, respectively. During leaf senescence, cytokinins reduce sugar accumulation, increase chlorophyll synthesis, and prolong the leaf photosynthetic period.

Detailed explanation-5: -Cytokinins are most abundant in growing tissues, such as roots, embryos, and fruits, where cell division is occurring. Cytokinins also delay senescence (aging) in leaf tissues, promote mitosis (cell division), and stimulate differentiation of the meristem in shoots and roots.