How plants keep other plants away

Allelopathy is a chemical process that a plant uses to keep other plants out of its space. There are several types of chemical alleopathy. In one kind, the plant that is protecting its space releases growth-compounds from its roots into the ground. New plants trying to grow near the allelopathic plant absorb those chemicals from the soil and are unable to live. A second type of allelopathy releases chemicals that slows or stops the process of photosynthesis . An allelopathic plant may also release chemicals that change the amount of chlorophyll a plant has in it. When a plant's chlorophyll levels are changed, it cannot make the food it needs, and the plant dies.

There are several ways in which an allelopathic plant can release its protective chemicals:

Volatilization
Allelopathic trees release a chemical in the form of a gas through small openings in their leaves. Other plants absorb the toxic chemical and die.
Leaching
All plants lose leaves. Some plants store protective chemicals in the leaves they drop. When the leaves fall to the ground, they decompose. As this happens, the leaves give off chemicals that protect the plant.
Exudation
Some plants release defensive chemicals into the soil through their roots. Those chemicals are absorbed by the roots of other trees near the allelopathic one. As a result, the non-allelopathic tree is damaged.

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