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In order to investigate the photoprotective function of photorespiration in grapevine under water stress, potted grapevines (Vitis vinifera L. cv. Cabernet Sauvignon) were randomly divided into three uniform groups for well-watered [watered every morning to keep the relative water content (RWC) of soil over 70 %], water-stress adapted (droughtadapted at 30 % relative soil water content for 30 days), and water stress without adaptation treatment (water-stressed to 30 % relative soil water content for 3 days). Net assimilation rate (A N ), stomatal conductance (g s ), substomatal CO 2 concentration (C i ), transpiration rate (E), actual photochemical efficiency of PSII (Φ PSII ), and maximum photochemical efficiency of PSII (F v /F m ) were recorded by combining measurements of gas exchange and chlorophyll fluorescence. Gross photorespiration (P r ), photosynthetic electron partitioning (J C /J T ), photochemical quenching coefficient (q P ), and non-photochemical quenching (NPQ) were also calculated. The ratio of net assimilation rate to transpiration rate (A N /E) was used as an indicator of water use efficiency (WUE). A N , apparent P r , Φ PSII , F v /F m , q P , and g s decreased, NPQ increased, and gross P r sustained at a high level under water stress. This suggests that both photorespiration and energy dissipation play important roles in protecting photosynthetic apparatus against photoinhibition. C i in water-stressed plants without adaptation treatment increased, which indicates the leaves suffered a non-stomatal limitation, while the water-stress adaped plants only suffered a stomatal limitation indicated by low C i .

In semi‐arid areas of north‐west China, grain yields of wheat (Triticum aestivum L.) are higher in recently bred cultivars than those released six decades earlier. The gas exchange, chloroplast activity and yield of six spring wheat cultivars grown in the 1950s, Hst and Gs96 (early), in the 1970s, Gy602 and Dx24 (intermediate), and in the 1990s, Gc20 and Lc8275 (modern) were compared with adequate water (WET) and drought stress (DRY) to determine the effects of drought stress among the cultivars. The results showed that in the WET treatment, the modern cultivars had significantly higher rates of leaf gas exchange, photosystem 2 (PS2) maximal photochemical efficiency, actual quantum yield of PS2 (ФPS2), photochemical quenching of chlorophyll (qp) and lower non‐photochemical quenching (NPQ) than early cultivars, but had significantly lower gas exchange rates, intercellular CO2 concentration, ФPS2, qp and NPQ in the DRY treatment. In the WET treatment, the grain yield of early cultivars was significantly lower (10 %) than intermediate cultivars, but was significantly higher (17 %) than intermediate cultivars in the DRY treatment. The modern and intermediate cultivars had more sensitive stomata to water shortage, but the decreased activity of the PS2 reaction centre helped avoid damage from photoinhibition in these cultivars.