Monday, November 13, 2006

Membrane Lipid Changes in Meyer and Cavalier Zoysiagrass during Cold Acclimation.

Qi Zhang, Kansas State University - Plant Pathology, Kansas State University, 2021 Throckmorton, Manhattan, KS 66506, Jack Fry, Kansas State University, 2021 Throckmorton Plant Sciences Ce, Manhattan, KS 66506, United States of America, and Channa Rajashekar, Kansas State Unvierity, 2021 Throckmorton Hall, Manhattan, KS 66506.

Changes in lipid composition influence membrane fluidity and are likely involved in cold acclimation and freezing tolerance. Lipid profiles and freezing tolerance were evaluated monthly on rhizomes of Meyer (Zoysia japonica) (cold tolerant) and Cavalier (Z. matrella) (cold sensitive) zoysiagrass plugs cold acclimated in the field in fall, 2005. Tmin (the lowest freezing temperature at which any recovery growth was observed) decreased from October to December in Meyer (from - 5 °C to –17 °C) and Cavalier (from –3 °C to –12 °C). Rhizome levels of phosphatidylcholine (PC), a bilayer-stabilizing lipid, were higher in Cavalier (30.5 %) than in Meyer (24.6 %) in November when Cavalier reached its maximum freezing tolerance (LT50 = -8.3 C). Conversely, PC level was higher in Meyer (27.3%) than in Cavalier (20.3%) when Meyer was most hardy in December (LT50 = -15.9 C). Phosphatidic acid (PA), which has been shown to increase following freezing injury, was negatively correlated with Tmin in Meyer and Cavalier (r = -0.94 and -0.84, respectively). Information on lipid changes during cold acclimation and freezing may be useful in selecting hardy zoysiagrass progeny.