Physiological responses of chickpea (Cicer arietinum) against chromium toxicity

Plant scientists are most concerned about metal toxicity and detoxification strategies because metals accumulate in plants and enter the food chain. To provide scientific references on metal detoxification strategies, we investigated the defense mechanism of chickpea as it can grow properly in a chromium-contaminated environment. Chickpea plants were grown on the hydroponic solution treated with chromium, and different biochemical analyses were conducted to determine the physiological responses to chromium toxicity. When the roots of chromium-treated seedlings were compared to control plants, they contained a significant amount (six times more) of chromium, but its translocation to shoots was limited, indicating the retention of excess chromium in roots. The reason behind this retention is chromium adsorption on the root surface as an attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) study reveal that roots induce divergent functional groups. Furthermore, the catalase (1.12 ± 6 × 10−2 U/min/mg) and peroxidase (0.97 ± 8 × 10−2 U/min/mg) enzyme activities play a partial role in removing oxidative stress in roots. However, no effective roles of exogenous salicylic acid (SA) and citric acid (CA) were observed in this mechanism. Findings of this study suggest that root-induced functional groups provide negative charges for the binding of chromium cations, resulting in the adsorption of chromium on the root surface. Adsorption of chromium due to surface charges preventing the entrance of chromium into plants may provide an avoidance strategy against chromium toxicity in local chickpea plants.