Relationship between various physiological and biochemical parameters activated by cadmium in Sinapis alba L. and Hordeum vulgare L.

The aim of this study was to examine the phytotoxicity of cadmium (Cd) on commonly measured physiological parameters [root and shoot growth inhibition, dry mass (DM) and fresh mass (FM) production, water content (WC), Cd accumulation] and biochemical parameters [photosynthetic pigments (chlorophyll a, b, total carotenoids), proteins, thiobarbituric acid reactive substances (TBARS), and protein sulfhydryl group content] using regression analyses. Biochemical parameters were evaluated to estimate oxidative stress in seedlings. For all parameters, the sensitivity of Hordeum vulgare L. and Sinapis alba L. plants was studied as representative of widely cultivated crop plants. Cd showed a greater inhibitory effect on root than shoot growth, predominantly in S. alba. In addition to growth inhibition, Cd reduced biomass production (FM, DM), mainly in the shoots. Although Cd was accumulated chiefly in the roots, the accumulation of Cd in S. alba shoots exceeded that in H. vulgare. While Cd resulted a greater reduction of chlorophyll b than chlorophyll a, carotenoids content in S. alba increased when metal concentration reached 71 and 143 mg Cd l−1. The adverse effect of Cd was also confirmed by a significant reduction in protein sulfhydryl groups. In a regression analysis, positive correlations were observed between proteins and sulfhydryl groups in shoots of S. alba and TBARS and sulfhydryl groups in H. vulgare, while negative correlations were found between Cd concentrations in S. alba roots and proteins, TBARS, and WC contents. Cd concentration in H. vulgare roots was also negatively correlated with TBARS and shoot length.