Effects of foliar application of nitrogen on the photosynthetic performance and growth of two fescue cultivars under heat stress

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 deg C (day/night) for two weeks. Shoot growth rate of both cultivars declined significantly under heat stress. N supply improved the growth rates, especially in the cv. Barlexas. Chl content, leaf net photosynthetic rate, stomatal conductance, water use efficiency, and the maximal efficiency of photosystem 2 photochemistry (Fv/Fm) also decreased less under heat stress when N was supplied than without N application. The efect was more pronounced in cv. Crossfire II. The variations in photosynthetic performance in the two cultivars studied were associated with their different response to heat stress and N fertilization, which were also evidenced by shoot growth rate and photosynthetic pigment contents.