Effect of summer high temperature on turf qualities of different Poa pratensis varieties

Nine Poa pratensis varieties were used to investigate their turf qualities including changes of turf coverage, tiller density, turf quality, SPAD, leaf width in the field during summer of Nanjing, and physiological characteristics such as water content and membrane permeability in leaves were measured in lab. The results showed that coverage, tiller density, turf quality, SPAD and water content of varieties declined significantly along with increase of heat and drought stress and persisting period. The membrane permeability in leaves increased remarkably and leaf width change was not significant. By hierarchical cluster analysis, the 9 P.pratensis varieties could be classified into three categories. Bluemoon and Park belonged to the first category which was weak in heat tolerance. Nuglade, America, Award, Liberator and Total belonged to the second category, they were mid heat tolerance varieties. Barrister and Nudesting belonged to the last category, and they had the strongest heat tolerance.