[Dynamic changes of photosynthetic characteristics in big-spike wheat yield formation]

A field experiment was conducted to investigate the yield traits, leaf photosynthetic rate, chlorophyll fluorescence parameters, chlorophyll content (Chl), and leaf area index (LAI) of eight new big-spike wheat lines, with multiple-spike cultivar Xinong 979 (Triticum aestivum cv. Xinong 979) as the control. The eight new lines had significantly higher kernel numbers per spike, kernel qualities, and 1000-grain mass but lower spike numbers per unit area, and the lines 2036, 2037, 2038, and 2040 had significantly higher yields than the control. The average net photosynthetic rate (P(n)) of the eight new lines had no significant difference with that of the control, but the PS II maximum energy conversion efficiency, PS II actual photochemical efficiency, photochemical quenching coefficient, and PS II reaction center activity of the lines were higher than those of the control. The leaf Chl of the lines 2037, 2040, 2039, 2038 and 2036 were 17.5%, 19.1%, 15.3%, 13.9%, and 7.9% higher than those of the control, and their LAI was significantly higher than that of the control and declined slowly in late growth period.