Photosynthetic ability of Horse gram [Macrotyloma uniflorum (Lam.) Verdc] plants in response to metal stress

Abstract

The effects of heavy metals' stress like aluminium (Al), bismuth (Bi), lithium (Li) and nickel (Ni) on photosynthetic ability of Horse gram plants inoculated with the four metal tolerant rhizobial strains were studied. Horse gram plants can grow in Al contaminated soils up to 400 μg g^–1, at this concentration also they have shown maximum PS ability than in uninoculated plants when they were inoculated with the strain HGR-13. In soils containing Bi, the rate of PS increased up to 200 μg g^–1 with the strain HGR-13 and 400 μg g^–1 with the strain HGR-25. Li has shown significant changes on PS ability of horse gram plants. The PS ability of these plants increased with the strain HGR-6 up to 30 μg g^–1 only. The plants inoculated with the strains HGR-4, 6 and 25 along with uninoculated plants have shown their maximum PS ability at 80 μg g^–1 of Ni. The net PS ability of HGR-4 and HGR-6 was maximum than uninoculated plants. In conclusion, these plants were able to grow in Al, Bi, Li and Ni contaminated soils. The metal tolerant rhizobial strains enhanced the PS ability of horse gram plants when they were inoculated in metal contaminated soils. Horse gram plants and the rhizobia associated with it besides having the nitrogen fixing ability, also have heavy metal tolerance. So, it is concluded that horse gram plants can be used as reclamation agents and phytoremediation.