Answer

Role of Cytokinins in Plant Physiology: Delay of Leaf Senescence

Cytokinins are a group of plant hormones involved in promoting cell division and growth. One of their significant physiological roles is the mobilization of nutrients, particularly during the aging process of plant tissues.

Nutrient Mobilization

Cytokinins enhance the redistribution of essential nutrients such as nitrogen, phosphorus, and potassium. This movement occurs from older, senescing leaves to younger, actively growing regions, helping sustain the metabolic activity of vital tissues.

Delay of Leaf Senescence

By maintaining nutrient levels in leaves, cytokinins help delay leaf senescence, which is the natural aging process characterized by chlorophyll breakdown, protein degradation, and cell death. Their actions include:

• Preserving chlorophyll content
• Maintaining protein and nucleic acid synthesis
• Sustaining photosynthetic efficiency

Practical Implications

In agriculture, cytokinins are utilized to:

• Prolong the shelf life of green leafy vegetables
• Enhance crop yield and quality
• Improve nutrient use efficiency in plants