Donna Asselin, age 7, of Springfield, Massachusetts, for her question:
Do trees need leaves to live?
A few plants manage to get along without leaves of any sort, but they tend to be rather small and shy. Certain other plants have thick green stems that pretend to be leaves. Some of them grow as tall as real leafy trees. But most trees need leaves to stay healthy and grow.
In mid winter, many of the trees are bare and their twigs seem to have no life in them at all. Actually, they are dozing, taking a long nap through the chilly months of the year. However, a tree cannot allow itself to fall into a deep deep sleep. So long as it lives, it must keep on growing. It must keep on adding new cells, new rings of wood around its trunk and twigs. In winter, this growing slows almost to a stop. This is because the tree needs its leaves to create the materials to build wood and shoots and roots.
The leaves of a tree are its kitchens, where amazing recipes are cooked up for dozens of different jobs. They are filled with wondrous stuff called chlorophyll that can make sugar from air, sunshine and moisture. This special sugar is the most important item in the diet of a tree. The tree has other magical recipes to change it into the sturdy material for build¬ing wood, or other materials for building roots and shoots and even more leaves filled with more chlorophyll.
Most chlorophyll is some shade of green and there is enough of it to color the leaves. And chlorophyll needs sunlight to fix up its sugary re¬cipe. The skies may be cloudy, but all day long there is enough sunlight to .keep the leafy kitchens busy. This sugar making goes on all through the summer days and the tree has plenty of food to grow and grow. It even has enough to store some groceries away to last through the winter.
Christmas trees and other evergreens have thick, sturdy leaves that can withstand the winter's cold. But many trees have thin, delicate leaves that would be frozen to icy fragments. These trees shed their leaves be¬fore winter comes. In the fall, the precious green chlorophyll breaks up and the leaves change to different colors. Finally they fall and the winter trees are left bare. But remember, their busy green leaves left them enough food to last. Some of this stored food will be used next spring to sprout new leaves to make more sugary food through the coming summer.
Green chlorophyll seems to be the only stuff in the world that can fix up the plant food recipe. But a few plants manage to live without real leaves. Cactus plants have chlorophyll in thick stems that look and act like leaves and some cactuses are tree sized. Mushrooms and toad¬stools have no chlorophyll at all. They depend on sugars that other plants have made. This is why they have to grow among fallen leaves and rotting tree trunks where they can find stores of ready made plant foods.