FREEZING TOLERANCE OF 3 ST-AUGUSTINEGRASS CULTIVARS AS AFFECTED BY STOLON CARBOHYDRATE AND WATER-CONTENT

Little is known about intraspecific variability in St. Augustinegrass [Stenotaphrum secundatum (Walt.) Kuntze] freezing tolerance and the ph ysiological factors that may influence survival. Stolons of field-grow n 'Raleigh', 'Floratam', and FX-332 St. Augustinegrass were sampled be tween October and March in 1990 to 1991 and 1991 to 1992 to measure fr eezing tolerance, nonstructural carbohydrates, and water content. Stol ons were exposed to temperatures between 1 and -8C in a freezer, and r egrowth was evaluated in the greenhouse. Generally, freezing tolerance of 'Raleigh' > 'Floratam' = FX-332. 'Raleigh' exhibited >60% survival in December and January, while survival of 'Floratam' and FX-332 was <20%. 'Raleigh' was the only cultivar that acclimated, as indicated by a 75% increase in survival between October and December 1990. Starch and sucrose were the primary storage carbohydrates extracted from stol ons, but neither was correlated with freezing tolerance. A negative (r = -0.80) correlation was observed between 'Raleigh' survival and stol on water content between January and March 1991. Reduced water content in 'Raleigh' stolons during winter months may contribute to acclimati on.