[Evolution characteristics of flag leaf photosynthesis and grain yield of wheat cultivars bred in different years].

Taking six winter wheat (Triticum aestivum) cultivars, i. e., 'Wangshuibai' and 'Bima 1' bred in 1950s, 'Zhengyin 1' and 'Yangmai 1' bred in 1970s, and 'Yumai 34' and 'Ningmai 9' bred in 1990s, as test materials, field experiments were conducted to study the evolution characteristics of their flag leaf photosynthesis and grain yield. The results showed that compared with those bred in 1950s and 1970s, the cultivars bred in 1990s had higher chlorophyll content, net photosynthetic rate (Pn), PS II maximum photochemical efficiency (Fv/Fm), actual photochemical efficiency (PhiPSII), photochemical quenching coefficient (qp) and non-photochemical quenching coefficient (qN) at grain-filling stage, their flag leaf had a longer functional duration and senesced slower, and their harvest indices were higher, with the grain yield increased by 25.90% and 11.29%, respectively. It was suggested that in the evolution process of wheat cultivars from 1950s to 1990s, the improved photosynthetic capacity and the lengthened functional duration of flag leaf after anthesis were the key physiological bases for grain yield enhancement.