Document Type : original paper
Authors
1
Sari Agricultural Sciences and Natural Resources University
2
Department of Agronomy - Sari Agricultural Sciences and Natural Resources University, Sari, Iran.
Abstract
Background and Objectives: Chromium (Cr) at higher concentrations acts as a major pollutant and heavy metal (HM), causing many environmental problems and contaminating the food chain. In plants, the toxic effects of Cr are also evident, exhibiting symptoms such as delayed germination, damaged roots and reduced root growth, decreased biomass, reduced plant height, photosynthesis, reduced grain yield and ultimately cause plant death. In recent years, the use of organic amendments such as biochar in HM-contaminated soils with a significant performance in the stabilization of HMs in soil and water has been considered. Therefore, the present research was conducted to investigate the use of different levels of rice straw-derived biochar in mitigating the negative effects of Cr in cowpea (V. unguiculata L.).
Materials and Methods: A factorial experiment based on a completely randomized design was used in 2023 at research greenhouse of Sari Agricultural Sciences and Natural Resources University. The treatments consisted of biochar (0, 1, 2 and 4 weight percent) and Cr (0, 2.5, 5, 10 and 25 mg kg-1) with three replications. In this experiment stem diameter (SD), plant height (PH), root and shoot dry weight (RDW and SDW), chlorophyll a, b (Chl a and b) and carotenoids (CAR), electrolyte leakage (EL), hydrogen peroxide (H2O2), the activity of catalase (CAT) and superoxide dismutase (SOD) were measured.
Results: Based on the findings, the interaction of the application of biochar levels in different concentrations of Cr showed a significant difference in all traits except for the SD trait. Increasing the Cr concentration adversely affected the studied traits, but the application of biochar could mitigate these negative effects and the best performance in all Cr levels was always observed at the 4-weight percent level of biochar. So that, the use of four weight percent biochar increased physiological traits including Chl a and b, CAR and EL by 92.88, 95.27, 95.36 and 63.94%, respectively. It also reduced the activity of CAT and SOD enzymes and H2O2 production by 4.88, 53.68 and 34.25 percent, respectively. In addition, between the activity of the two enzymes of CAT and SOD and the production of H2O2 with the SDW, a negative and significant correlation of (-0.89**, -0.85** and -0.81**) was observed, respectively.
Conclusion: Overall, increasing the concentration of Cr in the soil negatively affected all the studied morpho-physiological and biochemical traits and conversely, the use of different levels of biochar moderated the negative effects of chromium. The use of different levels of biochar improved these traits. The concentration of 25 mg/kg of Cr had the most negative effects, and at all levels of Cr, the level of 4 (weight percent) of biochar always had the best results in terms of evaluated parameter. According to the results of the current research, biochar can significantly improve the growth of the cowpea under Cr stress conditions.
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