Abstract: This paper analyzed the eco-physiological characteristics of spring wheat leaf photosynthesis in the semiarid rain-fed agriculture region of Loess Plateau, and their responses to the environmental factors. The results showed that the net photosynthetic rate (P_n) of spring wheat leaf had a diurnal change of typical two-hump curve, which was obviously higher before noon than after noon, and with a noon break. The appearing time of maximum P_n differed with growth stages. The transpiration rate (T_r) had a diurnal change of weak two-hump curve, and the appearing time of its maximum was later than that of maximum P_n. The P_n, T_r, and stomatal conductance (G_s) were affected by a combination of various environmental factors, with the dominant factor being different at different period, and even, the same factor having different effects on P_n, T_r and G_s. Among the affecting factors,photosynthetically active radiation (PAR) had the most intensive effect on T_r, and a close relation with P_n and T_r in the whole growth period. The effect of relative humidity (RH) on P_n was larger than that of temperature. Among P_n,T_r and G_s, the last two were the eco-physiological indexes most obviously affected by environmental factors.

Key words: Cucurbita moschata, Root exudates, Allelopathy, Orthogonal design