Temperature effects on membrane fatty acid composition of cotton

Chilling injury occurs in cotton seedlings whenever the temperature drops below 15°C for a few hours during the first few days of germination. The fatty acid composition of the lipid components is proposed to be related to chilling sensitivity- Plants with more unsaturated fatty acids in the lipid components are believed to have greater cold tolerance. An experiment was designed to test the effect of temperature on the fatty acid composition of germinating cotton seedlings. Seed were germinated in growth chambers under eight different day/night temperature regimes. Seedlings were harvested 4, 6, 8 and 10 days after planting, separated into three vigor classes based on hypocotyl length, and cut into cotyledon, hypocotyl and radical fractions. The phospholipid fractions were extracted from the hypocotyls and radicals, and the fatty acids were methylated to fomri fatty acid methyl esters which were analyzed by gas liquid chromatography. LInolenic acid (18:3) concentrations were higher in the longest seedlings regardless of temperature. Fatty acid composition in the hypocotyls was related to growth, suggesting that linolenic acid concentration is related to growth rather than to temperature. In the radicals, fatty acid composition was related only to vigor class and not related to growth or to temperature. The unsaturated/saturated ratio did not appear to be related to growth or to temperature.