ALLEVIATION OF NICKEL TOXICITY BY CALCIUM SALINITY

Abstract

Dose-response curves were obtained in a background of 1/10 strength Hoagland nutrient solution for lettuce seedlings with Ni at different background levels of CaCl2 and for CaCl2 at different background levels of Ni. Nickel showed a toxicity threshold at 20 μeq L−1 of Ni and a 50% reduction in yield at Ni concentrations of about 30 μeq L−1. However, if the available Ca was increased from that in the control 1/10 strength Hoagland solution of 1.0 to 257 meq L−1, most of the reduction in growth due to Ni toxicity at 30 μeq L−1 was reversed, giving a yield of better than 90% of control. This concentration of Ca (CaCl2) was where Ca started to have a salinity effect and further increases of Ca resulted in yield decrease due to salinity, so that any further alleviation of the Ni toxicity was not discernible. When an Ni dose-response curve was run in the presence of high background concentrations of Ca, Ni concentrations close to its toxic threshold level provided some alleviation of the salinity stress. These curves also showed a strong alleviation of Ni toxicity at high Ni concentrations in the presence of high background concentrations of Ca.