Photocontrol of Chlorophyll Loss in Papaya Leaf Discs

Both red and blue light pulses are separately shown to retarddark-stimulated chlorophyll loss of papaya leaf discs suggestingparticipation of phytochrome and blue light photoreceptors inregulating the pigment loss. The red light effect is fully reversibleby far-red light. The partial failure of far-red pulses to reversethe action of blue light suggests that blue light effect maynot be entirely through the phytochrome action. The apparentineffectiveness of continuous white light to check the chlorophyllloss is attributed to a balance of photooxidation and photoprotectionof the pigment. The interaction of blue light and kinetin at its different concentrationssuggests that the effect of interactions is additive. The bluelight effect in retarding chlorophyll loss is partly independentof the hormone level. (Received December 10, 1985; Accepted August 25, 1986)