Physiological basis of the difference in net photosynthetic rate of leavesbetween two maize strains

Significant differences in net photosynthetic rate (P-N) Of leaves between two maize (Zea may L.) strains (Shuang 105 and 40x44) grown in the field we re observed. At several growth stages, P-N of 40x44 was higher than that of Shuang 105 (from 10.3 to 32.5 %). Moreover, the strain 40x44 had a higher plant height, larger leaf area, lower chlorophyll content, and higher photo chemical efficiency of photosystem 2 (PS2) (F-v/F-m and DeltaF/F-m') than s train Shuang 105. Shuang 105, which showed lower P-N, had lower stomatal co nductances (g(s)) but slightly higher intercellular CO2 concentrations (C-i ) than those of 40x44. Hence the differences in P-N between the two strains did not result from the difference in g(s), but probably from that in ligh t reaction system.