Applying logistic equation to heat resistance study of coldseason ornamental grasses

High temperature was a major limiting factor for the growth of coolseason ornamental grasses in subtropical regions and tropical regions. The heat resistance (LT50) of six coldseason ornamental grasses was measured by determining the inflection point temperature through modified conductance ratio measurement combining with logistic equation, and the leaf was used to study. The result showed that the relationship between cell damage rate of leaf and temperature showed an obvious S curve through constant gradient treatment of high temperature, it was better fitting degree by according with logistic equation. Heat tolerance ability of materials was ranked as follows:Carex siderosticta (LT50=53.5 ℃) C.chungii (LT50=52.5 ℃)C.comans (LT50=51.5 ℃) C. muskingumensis (LT50=48.4 ℃)Dianthus gratianopolitanus (LT50=46.3 ℃)Phalaris arundinacea (LT50=44.8 ℃). Through the field observations of the material situation of oversummering in the Nanjing area, C.siderosticta, C.chungii, C.comans materials grew better than other grasses and had good appearance without any changes. Therefore, this study suggested that C.siderosticta,C.chungii, C.comans had strong heat resistance.