Senescence hormone is not a single, universally recognized term. Instead, several plant hormones are known to promote senescence (aging) in plants.
In plants, senescence is a highly regulated developmental process involving a cascade of physiological and biochemical changes that lead to the deterioration and eventual death of plant tissues or the whole plant. This process is influenced by both internal hormonal signals and external environmental cues.
While no single hormone is definitively labeled "the senescence hormone," the following are key players in promoting plant senescence:
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Ethylene: Often associated with fruit ripening and abscission (shedding of leaves, flowers, or fruit), ethylene also plays a crucial role in accelerating the senescence of leaves and flowers.
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Abscisic Acid (ABA): ABA is involved in stress responses and promotes senescence, particularly under conditions like drought or nutrient deficiency. It induces the expression of genes associated with senescence and chlorophyll degradation.
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Jasmonic Acid (JA): JA is involved in defense responses and senescence. It triggers the breakdown of chlorophyll and other cellular components.
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Salicylic Acid (SA): Primarily known for its role in plant defense against pathogens, SA can also induce senescence in certain plant tissues.
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Strigolactones (SLs): These hormones, known for their role in regulating shoot branching and root development, also contribute to leaf senescence.
In contrast, cytokinins (CKs) are known to inhibit senescence and promote cell division and growth. The balance between senescence-promoting and senescence-inhibiting hormones determines the timing and progression of senescence in plants.
It's important to note that the relative importance of each hormone in regulating senescence can vary depending on the plant species, tissue type, and environmental conditions. The process is complex and involves intricate interactions among different hormonal pathways and other regulatory mechanisms.
