A single-celled plant may have one large chloroplast, whereas the leaf cell of a multicelled plant may have as many as 20 to 100 chloroplasts. Chloroplasts are the plant organs in which photosynthesis takes place. Photosynthesis is the process by which green plants create food—specifically, they use the energy of the sunlight to convert water and carbon dioxide into carbohydrates and oxygen. Chloroplasts contain the green pigments chlorophyll a and b, which absorb the light energy used in photosynthesis.
Sources: Plants: Their Biology and Importance, pp. 17, 127; Villee, Claude A. Biology, 2nd ed., p. 107.