Chlorophyll is the substance that gives green plants their color, and which enables them to manufacture their own food. The chlorophyll absorbs certain rays of sunlight and uses the energy gained from these rays to join up, chemically, water and the gas carbon dioxide. By this means sugar and starch are produced, and the plant has manufactured its own food from simple chemical substances.
All animals are dependent, directly or indirectly, on this process for their food, for animals feed either on plants or on other animals. There are also larger numbers of plants which, since they are without chlorophyll, must also feed on other plants or animals. These are classified into two groups according to whether they feed on dead or living material; the former are called saprophytes, the latter parasites. Very few parasitic plants live on animals, but quite a large number feed on other living plants.
Saprophytic plants play an important role as they consume and clear away all the branches and leaves which fall from the trees, and which would otherwise cover the land.
Successive stages in the decay of a tree trunk
Let us look more closely at the way in which these 'natural scavengers' clear away the trees and branches and leaves that fall to the ground. We will follow the stages in the decomposition of a tree left lying on the ground.
The bacteria and fungi which live and feed in this way are called saprophytes (from the Greek sapron: a corpse) because they live on dead organic matter. In doing so they perform a service that is essential to life on earth, changing complex organic substances into simple mineral compounds and returning these to the soil so that they can be used again by green plants in the process of building up their tissues.
Related category• BOTANY
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