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

Abstract

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) (Fv/Fm and ΔF/Fm') 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.