Leaves

[karaturner]

Why do leaves fall off trees in autumn

[Sylday]

Well, in fact, the leaves only fall off deciduous trees; evergreen trees, such as pines, retain their leaves or needles. Why do the leaves fall in autumn? Presumably, because like most plants (at least those not in the tropics) they have a cycle which follows the seasons. New leaves develop in Spring, they gradually dry and age during the Summer and early Autumn, changing colour from green to brown (or red & gold); then fall off during late Autumn and Winter; before the cycle starts again in Spring.

[Clanad]

Actually, since the leaves cannot endure freezing and must be sealed off to insure the tree's survival. As sunlight decreases the veins that carry sap to the leaves gradually close off. A layer of cells forms at the base of the leaf stem and the leaf is separated from the tissue connecting it to the branch and it falls. Sylday is correct in stating this only happens to decidous trees.

[bernardo]

gravity

[woofgang]

my answer vanished!

[robber1]

Just for the sake of interest here, evergreens also loose leaves in winter. Thet dont lose as many as deciduous of course.