Question

Why leaves of plants fall off in a particular season?

Answer 1

Answer:

As day length shortens and temperatures cool, hormones within the plant are activated to begin the abscission process. ... These cells serve to slowly cut the leaf from the plant without leaving an open wound. As the leaves fall, the plant enters dormancy, saving its energy for the great bud burst of spring.

Answer 2

Answer:

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During the active growing season, production rates of auxin in leaves are consistent with other parts of the plant or tree. As long as these rates are steady, the cells of the abscission layer remain connected, which in turn, keeps leaves attached. However, as days shorten and temperatures cool, auxin production in leaves starts to decrease in response to changing conditions. As a result, fracture lines develop at the base of the leaf petioles and scarring builds up at the same point to form a protective barrier. Eventually, it’s just a matter of time before wind or rain provides that last nudge and the leaves are released, at least for most trees