The effect of light on chlorophyll loss in senescing leaves of sycamore (Acer pseudoplatanus L.).

Breakdown of chlorophylls in attached senescing sycamore leaves held in darkness was significantly less over a 14-d period than that occurring in leaves exposed to natural light. Chlorophyll a declined more rapidly than chlorophyll b in both situations, the stability of the latter being particularly increased in darkness. The differences between dark-maintained leaves and those exposed to light with respect to soluble protein, cytoplasmic RNA, and free amino-nitrogen were much less marked. The data indicate that chlorophyll loss during senescence is, at least in part, the result of a direct photochemical degradation of the pigment.