| Some physiological characteristics of leaf photosynthesis and environmental factors were measured both in grain filling stage and maturity stage on spring wheat field in semi-arid rain feed agriculture region in Loess Plateau.The results showed that the daily change of net photosynthetic rate (Pn) of leaf was a typical two-hump curve, there was a noon break.The Pn in a.m.was distinctly higher than in p.m., and the time at which the maximum appeared was different in differ growth stage.The daily transpiration rate (Tr) was a weak two-hump curve, and the time at which the maximum appeared lagged behind that of Pn.In addition, Pn, Tr and stomatal conductance (Gs) were affected by various environmental factors.At different period, the influence of major environmental factor on them was different;the same factor had a different effect on Pn, Tr and Gs. In these factors, PAR was the most intensive effect on Tr. In the whole growth period, they related closely with Pn and Tr. The effect of RH on Pn was more important than that of temperature. Among Pn, Tr and Gs, the last two were the most obvious ecophysiological factors affected by environmental factors.WUE of leaf was a weak two-hump curve.WUE in maturity stage was 46.2% lower than that in grain filling stage.Furthermore, the change of WUE was coincidental with precipitation in semi-arid rain feed region. |