The Effects of δ-Aminolevulinic Acid and Inhibitors of RNA and Protein Synthesis on Phytochrome Mediated Chlorophyll Accumulation inSorghum bicolor

Abstract

In 5 - d - old etiolated seedlings of Sorghum bicolor, 12 h of darkness after 5 min in red light eliminated a lag before the accumulation of chlorophylls in subsequent continuous white light. Increasing the dark period to 24 h and 36 h, increased the rate of chlorophyll accumulation in the later stages of greening. Exogenous δ - aminolevulinic acid neither completely removed the lag, nor increased the rate of chlorophyll accumulation. Cycloheximide (25 µg ml -1 ) and 6 - methyl purine (5.0 µg ml -1 ), given continuously or only until the 12 h dark period following the red light irradiation, restored the lag and decreased the rate of chlorophyll accumulation. D - threo - chloramphenicol (400 µg ml -1 ) also decreased the rate of chlorophyll accumulation but did not restore the lag. Addition of these inhibitors even 12 h after red light irradiation decreased the rate of chlorophyll accumulation. Rifampicin (Rifamycin SV, 400 µg ml -1 ) did not have such effects.