Cytokinin is the hormone that delays senescence in plants.
Cytokinins play a crucial role in regulating various aspects of plant growth and development, with one of their most prominent effects being the delay of senescence, which is the process of aging in plants. Here's a more detailed look:
Cytokinin's Role in Delaying Senescence
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Mechanism: Cytokinins primarily act by promoting cell division and preventing the breakdown of chlorophyll, proteins, and nucleic acids, all of which are hallmarks of senescence. They also influence nutrient mobilization, ensuring that nutrients are directed away from senescing tissues towards actively growing parts of the plant.
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Root-Shoot Communication: Cytokinins are synthesized mainly in the root apical meristems and transported to other parts of the plant via the xylem. This long-distance signaling allows the roots to communicate the plant's overall nutrient and water status to the shoots, influencing the rate of senescence. If roots are healthy and nutrients are abundant, cytokinins can promote continued growth and delay aging.
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Examples of Effects: Applying cytokinins to detached leaves, for example, can keep them green and metabolically active for a longer period, delaying the yellowing and wilting associated with senescence. In whole plants, elevated cytokinin levels can prolong the lifespan of leaves and fruits.
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Other Factors: While cytokinin is vital, senescence is a complex process influenced by other factors, including:
- Other hormones like ethylene and abscisic acid (ABA).
- Environmental conditions like light, temperature, and nutrient availability.
- Genetic factors that determine the plant's overall lifespan.
Cytokinin's Chemical Identity
Cytokinins are adenine-based compounds. One of the most well-known natural cytokinins is zeatin.
Importance for Plants
The ability of cytokinins to delay senescence has significant implications for plant productivity, especially in agriculture. By manipulating cytokinin levels or signaling, it may be possible to extend the shelf life of harvested crops and improve crop yields.
In summary, cytokinin is a key hormone in delaying senescence by promoting cell division, preventing the breakdown of vital cellular components, and influencing nutrient allocation within the plant.
