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
In contrast to primary growth, which makes a plant’s stem grow taller and its roots grow longer, secondary growth makes a plant grow wider. Primary growth occurs only through a plant’s shoot apical meristems, located at the tip of each branch, and root apical meristems, located at the tip of each root. By contrast, secondary growth occurs in the lateral meristems, which are found in the tree's trunk and branches.Full Answer >
To identify diseases in maple trees, examine the bark for cankers and lesions, check for signs of girdling roots and analyze the tree to see if verticillium wilt is present. The difficulty of the identification process depends on numerous factors, including the visibility of the symptoms.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 >
Plant growth is caused by water that is absorbed by the plant's roots and sunlight that spurs photosynthesis, which is the process of creating food for the plant. Plants also need space, time, clean air, healthy soil and nutrients to grow. The main ingredients that plants need are phosphorous, nitrogen and potassium.Full Answer >