The effects of nitrogen fertilization on the growth, photosynthetic pigment contents, gas exchange, and chlorophyll (Chl) fluorescence parameters in two tall fescue cultivars (Festuca arundinacea cv. Barlexas and Crossfire II) were investigated under heat stress at 38/30 °C (day/night) for two weeks. Shoot growth rate of two tall fescue cultivars declined significantly under heat stress, and N supply can improved the growth rates, especially for the Barlexas. Chl content, leaf net photosynthetic rate, stomatal conductance, water use efficiency, and the maximal efficiency of photosystem 2 photochemistry (F v /F m ) also decreased less under heat stress by N supply, especially in Crossfire II. Moreover, cultivar variations in photosynthetic performance were associated with their different response to heat stress and nitrogen fertilization, which were evidenced by shoot growth rate and photosynthetic pigment contents.

We studied the survival adaptation strategy of Sophora alopecuroides L. to habitat conditions in an arid desert riparian ecosystem. We examined the responses of heliotropic leaf movement to light conditions and their effects on plant photochemical performance. S. alopecuroides leaves did not show any observable nyctinastic movement but they presented sensitive diaheliotropic and paraheliotropic leaf movement in the forenoon and at midday. Solar radiation was a major factor inducing leaf movement, in addition, air temperature and vapour pressure deficit could also influence the heliotropic leaf movement in the afternoon. Both diaheliotropic leaf movement in the forenoon and paraheliotropic leaf movement at midday could help maintain higher photochemical efficiency and capability of light utilisation than fixed leaves. Paraheliotropic leaf movement at midday helped plants maintain a potentially higher photosynthetic capability and relieve a risk of photoinhibition. Our findings indicated the effective adaptation strategy of S. alopecuroides to high light, high temperature, and dry conditions in arid regions. This strategy can optimise the leaf energy balance and photochemical performance and ensure photosystem II function.