下层土壤容重对玉米生育后期光合特性和产量的影响

在耕层（0～20 cm）土壤容重不变情况下，采用池栽方法研究了下层（20～40 cm，40～60 cm）土壤容重变化对玉米生育后期光合特性和产量的影响.结果表明：当下层土壤容重不同时，玉米的光合速率（P_n）和产量都存在显著差异，随着下层土壤容重的增加，叶片P_n和产量降低，下层土壤容重越大，降幅越大.不同处理玉米叶片的P_n和细胞间隙CO₂浓度（C_i）的变化趋势不同，P_n早晨和傍晚较低，中午较高，且随着下层土壤容重的增加而降低, C_i的变化趋势则相反.气孔限制值（L_s）和气孔导度（G_s）也随着下层土壤容重的增加而降低. 随着玉米生育进程，P_n、L_s和G_s不断下降，而C_i不断升高.

Effects of subsoil bulk density on late growth stage photosynthetic characteristics and grain yield of maize (Zea mays L.).

A pool-culture experiment was conducted to study the effects of different subsoil bulk density at the depths of 20-40 and 40-60 cm on the late growth stage photosynthetic characteristics and grain yield of maize. The results showed that there existed significant differences in the net photosynthetic rate (Pn) and grain yield when the subsoil bulk density was differed. The Pn and grain yield decreased with increasing subsoil bulk density, and the higher the bulk density, the more significant the decrement in Pn and grain yield. The diurnal changes of Pn and intercellular CO2 concentration (Ci) were not in the same trend. Pn was high at noon and low at twilight and dusk, and decreased with increasing subsoil bulk density; while Ci was in adverse. The stomatal limitation (Ls) and stomatal conductance (Gs) also decreased with increasing subsoil bulk density. With the development of maize, the Pn, Ls and Gs, decreased gradually, while Ci increased continuously.