MOLECULAR-SPECIES OF PHOSPHATIDYLCHOLINE, PHOSPHATIDYLETHANOLAMINE AND DIGLYCERIDES OF TOMATO PERICARP DURING RIPENING, CHILLING AND SUBSEQUENT STORAGE AT 20-DEGREES-C

The molecular basis of chilling injury (CI) was investigated in mature -green tomato (Lycopersicon esculentum Mill. cv. Caruso) fruit. Presen t evidence identifies the cellular membranes, particularly those of th e chloroplast, as likely targets of the injury. Recent literature indi cates reduced galactolipid (GL) content in tomato pericarp, with littl e change in phospholipid (PL) content and fatty acid composition durin g exposure to low temperature. Wanner et al. (1991) report simultaneou s loss of GL and accumulation of polyunsaturated phosphatidylcholine ( PC) in senescent barley leaves. The present paper shows a similar shif t of PC toward less saturated molecular species during 18 d of chillin g at 1 degrees C and to a lesser extent during ripening at 20 degrees C. In contrast the molecular species of phosphatidylethanolamine (PE) showed the opposite trend during ripening and were little affected by low temperature. Diglyceride (DG) composition remained essentially unc hanged under these conditions. Four days after the fruits were transfe rred to 20 degrees C, the trend toward polyunsaturation of PC had been partly reversed, while the molecular species of PE and DGs were not m odified during the postchilling period. The molecular species profile of DGs was more similar to that of PLs than to that of GLs. The accumu lation of polyunsaturated PCs during chilling and their postchilling d egradation may explain why CI symptoms appear mainly after transfer of the fruits to a higher temperature.