Comparative on the heat tolerance and drought resistance of the roof greening plants Callisia repens and Sedum lineare

Roof greening is an effective method of improving the urban ecological environment, decelerating the urban heat island effect, and building low-carbon cities. High temperature and drought are the two most severe environmental stresses faced by roof greening plants. Callisia repens and Sedum lineare are two roof greening plants that are widely used in South China. In this study, the two plants were used as experimental materials to study their physiological responses to high temperature and drought stress under continuous high temperature treatments at 36, 40, and 44 ℃ for 5 days and continuous drought treatment for 25 days and a control treatment at a temperature of 30 ℃ and normal watering conditions. Measurements and comparative analyses of the soil water content and physiological indexes, including the plant tissue water content, relative conductivity, chlorophyll content, and malondialdehyde content of the two plants, were performed to determine the more suitable plant for roof greening in South China. The results showed that the physiological indexes of the two plants under high temperature and drought stress conditions presented consistent changes. Compared with Sedum lineare, Callisia repens showed high and stable tissue water content lower increases in relative conductivity and malondialdehyde content, and low chlorophyll content, indicating that its heat tolerance and drought resistance were stronger relative to that of Sedum lineare. Thus, Callisia repens is more suitable for roof greening in South China.