عنوان مقاله [English]
Low efficiency of phytoremediation process of some heavy metals in calcareous soils due to low mobility of these elements, has led to significant growth in research on the use of chelating agents and biostimulants to improve the efficiency of this process. In present study, the efficiency of cadmium (Cd) phytoremediation potential of Calendula officinalis L. was investigated in a Cd-spiked calcareous soil as affected by foliar and soil application of humic acid. For this purpose, in a greenhouse experiment, seedlings of C. officinalis were transferred to Cd-spiked soils (0, 50 and 100 mg kg-1) and treated separately with soil (soil drench) and foliar (spraying plant leaves) humic acid applications at different levels (0, 10, 20 M). The humic acid treatments were applied 2 weeks after transferring plant and eventually the various biochemical-physiological traits and phytoremediation indices of Cd in C. officinalis were measured at (specific) time points. According to the results, in Cd-spiked soils the C. officinalis apparently grew normally without any toxicity signs (chlorosis and necrosis symptoms), however with increasing the Cd levels, the dry weight biomass decreased and antioxidant enzymes activities (catalase, peroxidase, ) increased. Both foliar and soil humic acid application in Cd-spiked soils increased dry weight biomass, Cd concentration, and bioconcentration factor (BCF). Furthermore, the application of this organic substance, obviously moderated the Cd stress since the antioxidant enzymes activities reduced compared to the control. Based on the results, the obtained translocation factor (TF) and BCF values of Cd, which were >1, indicated that this plant is a Cd-hyperaccumulator, which could extract Cd via phytoextraction mechanism. Generally, among the humic acid treatments, application of 20 M (especially soil drench application) had the best effect on increasing Cd phytoremediation efficiency in the studied soil and it recommended to enhance the efficiency of Cd phytoremediation in calcareous soils.