Cadmium effects on carbonic anhydrase, photosynthesis, dry mass and antioxidative enzymes in wheat (Triticum aestivum) under low and sufficient zinc

Leaf carbonic anhydrase (CA) activity, net photosynthetic rate (P-N), stomatal conductance (g(S)) and plant dry mass (DM) exhibited a dose-dependent response to cadmium (Cd) in wheat (Triticum aestivum L.) grown under low and sufficient zinc (Zn) levels at 30 d after seedling emergence in sand culture. Cadmium at 10 mu M concentration enhanced CA, P-N and DM at low Zn level but these remain unaltered at sufficient Zn. Stomatal conductance decreased with increasing CdCl2 concentration at both the Zn levels. Cd higher than 10 mu M inhibited the characteristics irrespective of Zn level. The activity of superoxide dismutase (SOD) was not saturated the with highest Cd concentration (50 mu M) at both the Zn levels. However, the activities of ascorbate peroxidase (APX) and glutathione reductase (GR) increased up to 25 mu M Cd and decreased at 50 mu M Cd at both the Zn levels. It is suggested that CA activity was induced at low Cd (10 mu M) under low Zn level increasing the photosynthesis. The synergies among the activities of antioxidative enzymes helped to maintain CA and thus photosynthesis and plant DM at low Cd concentration under low Zn level.