Membrane Fatty Acid Composition and Saturation in Relation to Leaf Dehydration and Rehydration in Kentucky Bluegrass.

Membrane integrity and stability in leaves play critical roles in plant adaption to drought stress, which is largely influenced by lipid composition and saturation levels. The objective of this study was to investigate membrane lipid saturation level and fatty acids composition in relation to drought stress in leaves of two Kentucky bluegrass cultivars contrasting in drought tolerance. ‘Midnight’ and ‘Brilliant’ plants were maintained well-watered (control) or subjected to drought stress by withholding irrigation in a growth chamber. After 15 days of stress plants were re-watered partially to maintain soil water content at 50% of the control level. Leaf fatty acid compositions of the control, drought-stressed, and re-watered plants were analyzed. Physiological analysis indicated that ‘Brilliant’ was more sensitive to drought stress compared with ‘Midnight’. Both cultivars decreased in the degree of lipid unsaturation during drought stress, to a greater extent for ‘Brilliant’. Lipid unsaturation level resumed to the control level in ‘Midnight’ leaves, but did not fully recover in ‘Brilliant. The changes in the level of lipid composition in leaf membranes in both cultivars were mainly due to the changes in the composition of linolenic acids (18:3) and palmitic (16:0) and stearic (18:0) acids. Our results suggest that leaf dehydration and rehydration in Kentucky bluegrass was associated with their ability to maintain relative higher level of unsaturated fatty acids.