Membrane Fatty Acid Composition and Saturation Levels Associated with Leaf Dehydration Tolerance and Post-Drought Rehydration in Kentucky Bluegrass

Changes in fatty acid composition and saturation levels may be involved in leaf tolerance to dehydration during drought stress and recovery on rewatering. The objective of this study was to compare changes in compositional and saturation levels of leaf fatty acids between two cultivars of Kentucky bluegrass (Poa pratensis L.) contrasting in drought tolerance in response to drought stress and rewatering. Drought-tolerant 'Midnight' and sensitive 'Brilliant' were maintained well-watered (control) or subjected to drought for 15 d by withholding irrigation and then rewatered in a growth chamber. Compared to Brilliant, Midnight maintained higher turf quality, leaf photochemical efficiency, relative water content, and membrane stability expressed as electrolyte leakage during drought stress. Following rewatering, Midnight recovered more rapidly in each parameter than Brilliant. The degree of fatty acid unsaturation decreased in both cultivars during drought stress, and the decrease was less pronounced and occurred later in Midnight. Fatty acid unsaturation level resumed to the control level in Midnight leaves, but did not fully recover in Brilliant after rewatering. The alteration in fatty acid unsaturation level induced by drought and rewatering were mainly due to the changes in the composition of linolenic acids (18:3), linoleic acids (18:2), palmitic acids (16:0), and stearic acids (18:0). Our results suggest that leaf dehydration tolerance and postdrought recovery in Kentucky bluegrass was associated with their ability to maintain relative higher proportion and level of unsaturated fatty acids, particularly linolenic acids and linoleic acids.