Tree Transpiration – How does it work?

Do you know what tree transpiration is? Do you know why it’s so important? Well, we’re here to tell you. Tree transpiration is the process by which moisture (aka water) is carried through the tree from the roots to small pores on the underside of leaves. There it changes into vapor and is released into the atmosphere. About 10 percent of the moisture in the atmosphere is released by trees and plants through this process of transpiration. The remaining 90 percent is mainly supplied by evaporation by oceans, seas, rivers and other bodies of water.

But how does tree transpiration work exactly?

Let’s start by telling you that tree transpiration takes up about 98% of the tree’s energy. It’s obviously a vital function that the tree performs. For tree transpiration to occur, you need water. Water moves from the soil into the tree’s roots up through the trunk and into the leaves. The water, which is warmed by the sun, turns into vapor. Yes, it evaporates. It then passes out through thousands of tiny spores (stomata) which reside mostly on the underside of the leaf surface.

What are the two main functions of tree transpiration?

The two main functions of tree transpiration are cooling the tree and pumping water and minerals to the leaves for photosynthesis to occur. Trees need to cool themselves for several reasons. When temperatures are too high, energy systems, or metabolic functions, of the tree, will slow down. Growth slows down or stops. In extreme heat, trees become stressed and can die. Sometimes, heat bubbles can form that block the flow of water, leading to the tree becoming dehydrates. However, with tree transpiration occurring properly and regularly, that is less likely to happen.

How do trees, through transpiration, prevent dehydration?

Since tree transpiration is an evaporative cooling system that brings down the temperature of the tree, it must be regulated. Why? It can lead to water loss. Within the tree, there are guard cells on the stomata. When water moves into the guard cells, they swell and arch open. As water moves out, the guard cells relax and close. The guard cells are sensitive to light intensity, temperature, wind, relative humidity and carbon dioxide concentrations inside the leaf. The stomata must also open to take in carbon dioxide for photosynthesis, especially during the morning on sunny days. The more they are open, the more the tree will transpire and lose water. If you water your trees early in the morning, this will support plant energy especially during the summer.

How do trees pump water and minerals to leaves so photosynthesis can occur?

Trees pump water and minerals via transpiration similar to the way you suck liquid through a straw. Water and minerals move against the force of gravity and go up. The tiny capillaries called xylem are water channels via which water travels. Since water has an extremely strong bonding process, the sucking force created when water gets to the top of the channel causes its evaporation. However, the fact that the tree can create this force is due to negative pressure which lifts the column of water to the leaf surface.

We think tree transpiration is a miraculous thing. Don’t you think so too? We hope you enjoyed this article and learned something new about it. If you want, we also encourage you to read our articles on photosynthesis and tree respiration. All three processes form the tree’s water cycle. If you have questions or feel that your tree is not functioning properly, please call us at 512-341-8888. We can’t wait to help you out.