Comparative effect of organic amendments on physio-biochemical traits of young and old bean leaves grown under cadmium stress : a multivariate analysis

The current study investigated the influence of organic amendments on cadmium (Cd) uptake and its effects on biochemical attributes of young and old leaves of bean. Bean seedlings were exposed to two levels of Cd (25 and 100 μM) in the presence and absence of different levels of ethylenediaminetetraacetic acid (EDTA) and citric acid (CA). An increase in Cd concentration in growth medium significantly enhanced Cd accumulation in bean roots and shoot. Cadmium stress increased the production of H2O2 which resulted in lipid peroxidation and decreased chlorophyll contents. The presence of organic amendments significantly affected Cd accumulation and toxicity to bean plants. Application of EDTA alleviated Cd toxicity in terms of chlorophyll contents, H2O2 contents, and lipid peroxidation possibly by chelating toxic Cd ions, and as such forming Cd-EDTA complexes. The presence of CA decreased Cd toxicity by decreasing its uptake. The biochemical responses (H2O2 contents, lipid peroxidation, and chlorophyll contents) of bean plants were more severely affected by Cd treatments in old leaves compared to young leaves. This study shows that the effect of CA and EDTA on biochemical behavior of Cd varies greatly with applied levels of Cd and amendments as well as the age of leaves. Based on the results, it is proposed that the presence of organic amendments can greatly affect biogeochemical behavior of Cd in the soil-plant system (ecosystem).