Falling Leaves

Leaves 1The beautiful colors of fall sweep across the country. Come October and September, shades of red, orange, and yellow replace the bright green leaves of deciduous trees. We watch it happen but never question why. Why do the leaves fall from deciduous trees each autumn? You may think this is triggered by cooler temperatures since it happens in the fall as days grow shorter. However, many tropical trees also lose their leaves, but in the tropics, it coincides with the dry season, not changing temperatures. The real reason leaves fall is water conservation. Leaves have a large surface area from which water evaporates. When the ground freezes, plants cannot absorb water into the roots and evaporation without absorption will cause tissue damage. Therefore, plants retract energy and nutrients from the leaves, store it over the winter, and produce new leaves in the spring. Leaves are costly and take a lot of energy from a tree to support. Without retaining its leaves through the winter, deciduous trees can conserve more water, and therefore, better survive until more favorable conditions exist. Each tree will regrow its leaves when spring arrives and there is more water available.

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