Growth, tolerance efficiency and phytoremediation potential of Ricinus communis (L.) and Brassica juncea (L.) in salinity and drought affected cadmium contaminated soil.

We have previously reported that Ricinus communis (castor) is more tolerant to soil cadmium (Cd) and more efficient for Cd phytoremediation than Brassica juncea (Indian mustard) (Bauddh and Singh, 2012). In the present study, R. communis was found more tolerant to salinity and drought in presence of Cd and removed more Cd in a given time than Indian mustard. R. communis produced 23 and twelve folds higher biomass in terms of fresh weight and dry weight, respectively than that in B. juncea during three months when grown in Cd contaminated soil in presence of 100mM NaCl salinity and ten day water withdrawal based drought at 90 day after sowing (DAS). Castor plants showed stronger self-protection ability in form of proline bioaccumulation (r(2)=0.949) than Indian mustard (r(2)=0.932), whereas a lower r(2) for malondialdehyde (MDA) and total soluble protein in R. communis (r(2)=0.914 and r(2)=0.915, respectively) than that of B. juncea (r(2)=0.947 and r(2)=0.927, respectively) indicated a greater damage to cell membrane in Indian mustard during the multiple stress conditions. Though, the amount of Cd accumulated in the roots and shoots of Indian mustard was higher as per unit biomass than that in castor, total removal of the metal from soil was much higher in castor on per plant basis in the same period in presence of the stresses. R. communis accumulated about seventeen and 1.5 fold higher Cd in their roots and shoots, respectively than that of B. juncea in 90 DAS under the multiple stresses. Salinity alone enhanced Cd uptake, whereas drought stress reduced its uptake in both the plants.