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RESEARCH PRODUCT

Effect of Light on the Composition of Mitochondrial Lipids from Hypocotyl Hooks of Bean Seedlings (Phaseolus vulgaris L.).

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Summary Mitochondria were isolated and roughly purified from bean seedlings (phaseolus vulgaris) treated with different red light (660 nm) irradiation programmes. Etiolated seedlings were irradiated for short terms or grown in red light. The mitochondria from differently treated seedlings were analysed for their phospholipid and fatty acid patterns. The mitochondrial phospholipid patterns from green and etiolated seedlings were rather similar. This was also valid for the fatty acids from the phospholipid fraction whereas the fatty acid patterns of the glycolipids showed differences. Remarkable changes were observed in the phospholipid pattern of the mitochondrial fraction after short-term irradiation of the seedlings. Labelling experiments with 32 P for 1 h demonstrated a decreased specific activity of the mitochondrial phospholipids compared with the non-irradiated controls. The phosphatidic acid content of our preparations was rather high, indicating hydrolytic activity of phospholipase D. P-chloromercuribenzoate, an inhibitor of phospholipase D, did not change the levels of phosphatidic acid. A protection medium according to Morre and Scherer (1978) decreased the phosphatidic acid content in preparations from etiolated but not from green material. The results are discussed in relation to the influence of short term irradiations mediating respiration rates.