CALCIUM DELAYS SENESCENCE-RELATED MEMBRANE LIPID CHANGES AND INCREASES NET SYNTHESIS OF MEMBRANE LIPID COMPONENTS IN SHREDDED CARROTS

The influence of Ca2+ on firmness and membrane lipid structural compon ents was evaluated during storage of shredded (wound-stressed) carrot tissues (Daucus carota L. 'Caropak'). During 10 days of storage at 10 degrees C and 95% RH, Ca2+ treatment (applied as 1% w/v CaCl2 upon shr edding) provided 6-16% greater firmness retention than did a water con trol treatment. Calcium accentuated net increases in total phospholipi d and monogalactosyldiacylglycerol concentrations after 4 and 10 days of storage, and in acylated steryl glycoside concentrations after 4 da ys of storage. Calcium partially counteracted a net reduction in stery l glycoside concentration which occurred following 4 days of storage, and prevented an increase in the free sterol:phospholipid ratio follow ing 10 days of storage, Calcium preserved membrane integrity of carrot shreds not only by delaying senescence-related membrane lipid changes , but also by apparently augmenting membrane restructuring processes.