Physiological Basis of the Difference in Net Photosynthetic Rate of Leaves between Two Maize Strains

Significant differences in net photosynthetic rate (P_N) of leaves between two maize (Zea mays L.) strains (Shuang 105 and 40×44) grown in the field were observed. At several growth stages, P_N of 40×44 was higher than that of Shuang 105 (from 10.3 to 32.5 %). Moreover, the strain 40×44 had a higher plant height, larger leaf area, lower chlorophyll content, and higher photochemical efficiency of photosystem 2 (PS2) (F_v/F_m and F/F_m) than strain Shuang 105. Shuang 105, which showed lower P_N, had lower stomatal conductances (g_s) but slightly higher intercellular CO₂ concentrations (C_i) than those of 40×44. Hence the differences in P_N between the two strains did not result from the difference in g_s, but probably from that in light reaction system.