Q.(a) Write the physiological effects of Cytokinins. OR
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Start your 14-day free trial to unlock the full solution →Cytokinins are a class of plant hormones (e.g., kinetin, zeatin, 6-BAP) whose defining role is promoting cell division, and which additionally delay senescence, break dormancy, counter apical dominance, and, together with auxin, control organ formation in tissue culture.
Cytokinins are a group of plant growth hormones named for their central role in promoting cytokinesis (cell division). They are synthesised mainly in actively dividing tissues, especially root tips, and are transported upward via the xylem. Their major physiological effects include:
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Promotion of cell division: cytokinins stimulate cell division by regulating the cell cycle, working together with auxin in the correct ratio to trigger mitosis in target tissues.
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Delay of senescence (Richmond–Lang effect): applying cytokinin to a detached leaf (or a region of an intact leaf) delays its yellowing/senescence, apparently by mobilising nutrients toward the treated area and maintaining protein/chlorophyll synthesis. This is exploited commercially to keep cut flowers and vegetables fresh longer.
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Breaking dormancy: cytokinins can break the dormancy of some seeds and lateral buds, promoting their germination/sprouting.
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Overcoming apical dominance: cytokinins antagonise auxin's suppression of lateral (axillary) buds — applying cytokinin to a lateral bud can cause it to grow out even in the presence of an intact apical bud, promoting a bushier growth habit.
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Promotion of chloroplast development and greening: cytokinins stimulate chlorophyll synthesis and chloroplast maturation, and can delay the yellowing of leaves.
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