The New Student's Reference Work/Chlorophyll

Chlorophyll (klō′rō-fĭl), the green coloring matter of plants. It is found associated FIG. I with protoplasm, usually in special bodies called chloroplasts or chlorophyll bodies, which are found only in cells near the surface of parts exposed to light, e. g., in leaves and twigs. These are usually rounded granules much too small to be seen with the naked eye (see Fig. I). In some algæ they are much larger, and have curious shapes. Little is known with certainty of the chemical nature of chlorophyll, because it easily decomposes. Besides the pure green coloring matter (to which the name chlorophyll may be restricted), yellow pigments (carotin or xanthophyll) are associated with it in the mosses, ferns and seed-plants. In some algæ browns or blues or reds may be present also. The green pigment particularly (and in part the others) enables the plant to absorb certain portions of the light. The energy thus gained is partly used in the making of new foods (see Photosynthesis). In the absence of chlorophyll, this work cannot be accomplished. Chlorophyll is probably being continuously produced and destroyed in green plants. It is not usually formed in darkness, and if light is excluded from a green plant the destruction of the chlorophyll leaves it a pale yellow. Autumnal colors are due in part to the decomposition of the chlorophyll.

Chloroplasts: (a) Position in cells. (b) Isolated.