Transpiration pull theory is the proposed mechanism by which trees draw water through their roots. Transpiration occurs when the leaves of a tree allow water to exit into the air by means of tiny holes called stomata. When the water exits the leaves, the combination of capillary action, cohesion and adhesion draws more water up through the plant's roots to replace the released water.Know More
Capillary action is the tendency for liquids, such as water, to climb the sides of narrow tubes. Tree wood, which is called xylem, contains numerous capillary-like structures for drawing up the water. Cohesion and adhesion refer to the tendency for water to bond with itself and other substances, respectively.
Small structures called guard cells surround each individual stoma; these cells open and close the holes as necessary to regulate the amount of water exiting the leaves. The rate of transpiration varies with the seasons and time of day. During the winter, deciduous trees shed their leaves to avoid desiccating.
This mechanism of drawing water from the ground is entirely passive. Trees expend no energy hydrating themselves. However, this method places an upper limit on the height of trees, as the tension on the water column can break, resulting in air bubbles. These bubbles compromise the capillaries and damage the tree.Learn more about Botany
One adaptation that oak trees exhibit is very deep root systems, which help them find water. This is especially useful in a habitat that's prone to drought. The leaves of many oaks are thick and have small stomata, which reduces the rate of evaporation and water use.Full Answer >
When the relative humidity in a plant's environment rises, its rate of transpiration lowers, and a decrease in humidity causes the transpiration rate to rise. Air that is humid does not accept water vapor easily, and drier air makes it easier for a plant to release water by evaporation through the stomata on its external surfaces. Because drier air can account for drier soil conditions, the water uptake portion of the transpiration process may also increase as the plant attempts to bring in more water through its root system.Full Answer >
Plants respond to gravity by consistently causing their roots to grown downward and their stems to grow upward by sensing the direction of gravity with the use of tiny starch granules within specialized cells. This growth in response to gravity is known as gravitropism.Full Answer >
There are several places where plants store food, the most common being in the roots or in their fruit. One way of knowing where the food stores are is by observing which parts of the plant are eaten by animals.Full Answer >