EFFECTS OF GROWTH CONDITIONS AND RIPENING ON PLASTID AND MICROSOMAL MEMBRANE LIPID COMPOSITION IN BELL PEPPER FRUIT

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  • 1 USDA, Agricultural Res. Service, Hort. Crops Quality Laboratory, Beltsville, MD 20705

Plastids and microsomal membranes were isolated from pericarp tissue of mature green and red-ripe tell pepper fruit harvested from greenhouse and field grown plants. The lipid composition of these membrane fractions changed far more with ripening of field grown than greenhouse grown fruit. Also, the phospholipid (PL), free sterol (FS), steryl glycoside (SG) and acylated steryl glycoside (ASG) content of microsomes and plastids from both green and red fruit were very different under the two growing conditions. Total steryl lipids (TSL = FS + SG + ASG), and the TSL/PL ratio, increased in microsomes and decreased in plastids with ripening. These changes were much greater in field grown fruit. The ASG/SG ratio decreased with ripening in both membrane fractions, under both growing conditions. Ripening and growth conditions affected the phospholipid and sterol composition in plastids much more than in microsomes. Lipid changes associated with the chloroplast – chromoplast transformation were similar in field and greenhouse grown fruit, including an increase in the galactolipid/PL ratio. Future studies will assess how differences in membrane lipid composition affect postharvest storage life of the fruit.

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