AbstractThe effects of red and blue light on the formation of chlorophyll in excised roots of cucumber and pea was investigated and compared with previously reported experiments on wheat roots. All three kinds of roots are similar in that in continuous red light no or very little chlorophyll is formed. and in blue light a considerable amount of chlorophyll is produced. Roots of cucumber and pea differ from those of wheat, in that red light is ineffective (or nearly so) even when combined with blue.