Management of chromium (VI) toxicity by calcium and sulfur in tomato and brinjal: Implication of nitric oxide.

To reduce pressure of toxic metals on crop plants, several strategies are being employed of which nutrient management is gaining much importance. Moreover, whether nitric oxide (NO), has any role in nutrients-mediated management/amelioration of metal toxicity is still not known. Therefore, the role of Ca and S in managing Cr(VI) toxicity was investigated in tomato and brinjal with an emphasis on possible involvement of NO. Cr(VI) reduced growth in both vegetables which was accompanied by increased accumulation of Cr(VI), lignin and reactive oxygen species (ROS), and altered cell cycle dynamics and photochemistry of photosynthesis. However, external addition of either Ca or S reversed these effects and hence improved growth noticed in both vegetables. Cr(VI) toxicity was further increased by NG-nitro-l-arginine methyl ester even with additional Ca and S while sodium nitroprusside either restored growth up to the control level or increased it in both vegetables, even in the presence of L-NAME, suggesting that NO might have a positive role in nutrients-mediated management/amelioration of Cr(VI) toxicity. In this study, role of Ca, S and NO with reference to Cr(VI) and NO accumulation, components of phenylpropanoid pathway, cell cycle dynamics, photosynthesis, ROS and antioxidant potential in managing Cr(VI) toxicity is discussed.