Why Does a Tree Grow Upward?
The first thing to say in answering this question is that the whole tree does not grow up. Part of the tree grows downward, and that is the root. Each grows to the place where it can do the work for which it was made. In the seed from which the tree grows there are certain cells which are meant to form the part of the tree that is to live in the air and the light. Wherever the light is, they grow toward it. On the other hand, there are other cells which grow best in the dark, and which even seem to be affected by the gravitation of the earth, so that they grow best toward the centre of the earth.
So the tree - and this is true of nearly all plants - has two parts: one that lives in the air, and one that lives in the soil. Neither part could live without the other, and the tree is so made from the first that the right part of it, that which is capable of making leaves, must grow upward into the light and air; while that part of it which can suck up water and salts, and also can hold firm, must grow downward into the earth. So, in whatever position you plant a seed, when it sprouts the young shoot will grow upward and the young root downward.
