Many people believe tree leaves fall and die during the autumn season because of weather changes, but studies have shown the real reason for the fall is drought. This is because the primary function of leaves is photosynthesis, and photosynthesis requires the use of water, carbon dioxide and light to create food in the leaves to generate organic compounds and oxygen. In order to induce a suction force, the leaves will need to constantly sweat, and in winter season shed them so as not to get dried. Daylight, however, gets shorter during fall and causes the leaves to suffer thirst because of the reducing absorption of water with the shrinking daylight. This means even when trees live in wet climate with abundant snowfall and rainfall or even when in the warmest of autumn seasons, the trees will still lose their leaves, triggered by the shorten length of daylight.
Many changes occur in the leaves before they finally fall from the branch. According to Joe Lamp’L of DIY Network who wrote an article on ‘Why do leaves fall in autumn?’ at ScrippsNews.com, changing colors of leaves during fall is part of an important and complicated process known as abscission which ends in the leaves being shed at the end of each growing season. The trees, in protecting themselves, purge diseased, damaged or dead leaves, while they seal the point where the petiole connects to it. As the climate and light conditions of autumn evolve, tree hormones change as well, the most notable of which is auxin, a hormone in trees that promotes root formation and bud growth. The balance of auxin levels between leaves and branches is the key to determining if and when the leaves drop.
During the active growing season, production rates of auxin in leaves are consistent with those in other parts of the 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. 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.
Although leaves falling in autumn are a predictable event, leaf drop is not only seasonal. Trees can lose leaves for other reasons as well, such as drought and other physical or environmental stresses. So this autumn, enjoy and savor the brilliant display of color, but be thankful always for the deciduous trees, because in spite of all the leaves on the ground, they are doing more good than you can imagine, because these leaves provide vital organic matter to the soil, returning to the soil nutrients and building structure and water holding capacity.
Have fun, tak tons of pics and post 'em!!!
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