Lipids of chill-sensitive and -resistant Passiflora species: Fatty acid composition and temperature dependence of spin label motion

Polar lipids were extracted from the leaves of Passiflora species which varied in their resistance to chilling injury. The fatty acid compositions of the 8 major polar lipid classes from P. caerulea (chill-resistant) were generally similar to those of the corresponding lipids from P. flavicarpa (chill-sensitive). Using ESR spectroscopy, the motion of spin-labelled molecules was measured in phospholipids isolated from a range of Passiflora species. The temperature dependence of the motion of the spin labels showed a change at 1° for lipids of the most chill-resistant species and at 9° for the lipids of the most chill-sensitive species. Lipids from other species showed changes at intermediate temperatures, and the greater the chilling sensitivity of the species, the higher was the temperature of the change. It is concluded that pronounced differences in chilling sensitivity of the Passiflora species are correlated with physical differences in their membrane lipids; however, the degree of unsaturation of the lipids is not a reliable guide to chilling sensitivity.