Effects of water stress on photosynthesis and nitrogen metabolism in vegetative and reproductive shoots of <Emphasis Type="Italic">Leymus chinensis</Emphasis>

In Leymus chinensis, mild water stress (soil moisture 60–65 % of field capacity) had no significant effects on nitrogen metabolism, photosynthesis, and chlorophyll fluorescence. Severe water stress (35–40 %) significantly decreased the activities of nitrate reductase, glutamine synthetase, and glutamate dehydrogenase, net photosynthetic rate, stomatal conductance, transpiration rate, maximal efficiency of photosystem 2 photochemistry (F_v/F_m), actual quantum yield, and photochemical quenching, but increased the endopeptidase activity and malondialdehyde contents. The adverse effects on photosynthesis and N metabolism were markedly greater in reproductive shoots than in vegetative shoots.