Membrane Polar Lipid Changes in Zoysiagrass Rhizomes and Their Potential Role in Freezing Tolerance

Cell membranes play an integral role in freezing tolerance. The objectives of this study were to quantify polar lipids in cold-tolerant 'Meyer' zoysiagrass (Zoysia japonica) and cold-sensitive 'Cavalier' zoysiagrass (Zoysia matrella) and to evaluate their potential role in freezing tolerance. Grasses were acclimated outside and sampled once monthly between October and January to determine freezing tolerance and lipid composition in rhizomes. Lowest LT(50)s (temperature resulting in 50% survival) Were observed in November for 'Cavalier' (-8.5 and -9.6 degrees C in 2005 and 2006, respectively) and December for 'Meyer' (-16.2 and 15.4 degrees C in 2005 and 2006, respectively). The most abundant lipids in zoysiagrass rhizomes were monogalactosyl diacylglycerol, digalactosyl diacylglycerol, phosphatidylcholine, phosphatidylethanolamine, and phosphatidic acid, which comprised 90% of the polar lipids. Differences in lipid contents and double bond indices (DBI) were detected between 'Meyer' and 'Cavalier' during cold acclimation, but there were no consistent relationships between lipid classes or DBI and freezing tolerance in zoysia grass.