[Differentiation of chloroplasts in excised roots]

Illumination with blue light (350-550nm) of excised roots isolated from etiolated pea seedlings (var. Alaska) induces chloroplast formation in the cells of the innermost cortex within 72 h. After 5 days in blue light chloroplasts also appear in the parenchymatic cells of the vascular cylinder. Red light (600-700 nm) of equal energy, however, fails to initiate any chloroplast development in the roots, in contrast to the effect of red light on the same process in leaves. Accordingly it is assumed that two different photoreactive systems are involved in chloroplast differentiation.