Anyone who has visited Hainan Island has seen beautiful coconut trees. With their straight, upright trunks and no branches around, they only have large leaves several meters long at the top of the trunk, which look like many huge green feathers spreading out. Coconut trees standing by the sea have become a classic scene of southern scenery. People admire the beauty of coconut trees, but few people know: Why do its leaves grow differently from ordinary trees, all on the top of the trunk?
Some people say that because coconut trees don't have branches, they can only grow this way. So why don't coconut trees grow branches around them? Botanists tell us that there is a layer of highly dividing cells between the bark and the woody part of most trees, called the cambium in plant morphology. Through division activities, it continuously forms new phloem cells outward and new xylem cells inward, so that the stem of the plant can continuously thicken and grow, forming thick wood. However, coconut trees don't have a cambium. Their stems are composed of many fibrous vascular bundles, so the thickness of the stem from the base to the top is basically the same. Since the branches of trees are gradually formed by the sprouting of lateral buds, and coconut trees have no lateral buds or growth points around their stems, only a growth point at the top of the stem, coconut trees can only grow straight up and cannot grow branches around them.
If we observe the entire growth process of coconut trees, we can explain the whole problem more clearly. In the early stage of coconut tree growth, it only has a short stem, and although the leaves are also at the top, it seems that all parts of the tree are covered with leaves. As coconut trees grow older, their stems continue to extend upward and become longer and longer, and the old leaves continue to fall off, while new leaves continue to grow. The coconut leaves at the top of the stem become higher and higher. In fact, on the surface of every adult coconut tree trunk, there are horizontal stripes, which are the annular leaf scars left after the old leaves fall off. Interestingly, these annular leaf scars just provide a "place to step on" for people to pick coconuts.