why do some trees lose their leaves in autumn
Answers
Explanation:
As winter descends, trees in temperate and boreal zones face punishingly cold temperatures and frigid winds, conditions that would damage leaves, so trees have to reduce themselves to their toughest parts—stems, trunks, branches, bark. Leaves must fall.
Evergreens can hang on to their leaves through winter, because their foliage is coated in a wax that helps protect against cold, and their cells bear anti-freeze chemicals that ward off winter’s worst woes. Not so for broadleaf, or deciduous, trees. The fluids that flow through their leaves are thin and susceptible to freezing, the tissues tender. Winter cold dooms the leaves, and trees save energy by getting rid of them. Let’s take a look at the process.
As the dark mantle of winter’s dwindling days falls, trees can sense the loss of light. Thanks to chemical light receptors—phytochrome, which detects red light, and cryptochrome, which is sensitive to blue—trees can register day-length changes of as little as half an hour. When they do, they undergo chemical and physical changes that produce autumn hues.
Answer:
to save water by losing their leaves