Effects of high temperature shock on growth and physiological response of Zoysia tenuifolia seedlings

Based on the climate characteristics of subtropical regions, five high temperature gradients (36℃, 38℃, 40℃, 42℃, 44℃) were set up to shock Zoysia tenuifolia seedlings for 30 days (2 h/d). The effects of the shocks on growth and physiological response of Z. tenuifolia seedlings were studied by measuring plant height, tiller number, leaf area, biomass, chlorophyll and physiological active substance content. The results showed that: (1) High temperature shock significantly affected the morphological indicators, with plant height, leaf number, and total leaf area decreased at ≥38℃, but tiller number decreased at ≥40℃. The impact on morphological indicators was as follows: total leaf area>tiller number>plant height>leaf number>leaf thickness. (2) High temperature shock significantly affected biomass accumulation and distribution, when ≥40℃ total biomass and root to shoot ratio decreased, with biomass preferentially distributed to the aboveground portion. (3) High temperature shock significantly affected chlorophyll content, with a decrease in chlorophyll a content at ≥ 38℃ and a decrease in chlorophyll b at ≥40℃,but chlorophyll a/b was less affected. (4) High temperature shock significantly affected physiological substances. The higher the temperature was, the greater the activity of SOD and POD was, as well as the content of MDA and Pro. The magnitude of the impact was MDA>POD>SOD>Pro>CAT. The response of resistant substance content to different high temperatures varies greatly. In summary, high temperature shock affected the growth, meristem, and photosynthetic capacity of Z. tenuifolia. By regulating resistant substances to resist high temperature damage, it can withstand 44℃ high temperature shock and safely survive the summer.