干旱区生态环境知识资源中心

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 (?PS2), photochemical quenching of chlorophyll ((q)p) and lower non-photochemical quenching (NPQ) than early cultivars, but had significantly lower gas exchange rates, intercellular CO2 concentration, ?PS2, (q)p 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.