Abstract
Cadmium (Cd) contamination in soil adversely affects crop productivity, grain quality, and human health. Applications of boron (B) and biochar are known to impart tolerance to crops against abiotic stresses. A pot experiment was performed to assess the effects of the sole and combined application of B and biochar on growth, physiological and antioxidant defense mechanisms, yield, and grain quality of wheat under Cd toxicity-induced stress. The treatments included control (0 mg kg−1 and 0 g kg−1), only Cd (15 mg kg−1), only B (5 g kg−1), only biochar (50 g kg−1), B plus biochar, Cd plus B, Cd plus biochar, and Cd plus B plus biochar, which were applied at the time of sowing and were arranged using completely randomized design (CRD) with five replications. The individual Cd toxicity (15 mg kg−1) significantly reduced chl a, chl b, and chl a+b, as well as primary metabolites (soluble protein, amino acids, total soluble sugar, and phenolic contents), while it increased the activities of enzymatic antioxidants like superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APX) in the leaves of wheat. In addition, Cd stress (15 mg kg−1) increased lipid peroxidation in the form of malondialdehyde (MDA), and it enhanced the hydrogen peroxide (H2O2) content, electrolyte leakage (EL), and proline contents in the leaves. Furthermore, Cd (15 mg kg−1) contamination reduced the grain yield and yield-related attributes relative to respective no-Cd treatments. Soil-applied B and biochar improved wheat grain yield by triggering the activities of enzymatic antioxidants. Individual or combined B and biochar applications improved proline contents and reduced H2O2 and MDA contents in plants. The combined application of B and biochar enhanced soluble sugars and total phenolic as compared to the control and Cd-contaminated plants. In conclusion, the combined application of B and biochar was found to be the best soil amendment strategy to improve the yield of wheat under Cd-contaminated soil.
Highlights
Cadmium (Cd) is one of the main hazardous elements and is generally considered the most toxic element in cereal crops [1]
Cadmium stress had a drastic effect on plant growth parameters, and it significantly reduced plant height by 16.57%, spike length by 15.58%, grains per spike by 16.43%, 100grain weight by 14.54%, and grain yield per plant by 16.33%, as compared to the control (Figures 1 and 2)
The maximum results were observed when the combined application of boron and biochar was done on wheat plants
Summary
Cadmium (Cd) is one of the main hazardous elements and is generally considered the most toxic element in cereal crops [1]. Cd toxicity hinders the growth and development of plants, which reduces their morphological and yield attributes. Cadmium (Cd) affects the physiochemical and biological processes in plants which disrupt plants vegetative growth and development, leading to decreased grain yields and lowered grain quality [3]. Cadmium (Cd) induced oxidative stress hinders antioxidant defense systems in crop plants [4]. Due to cadmium (Cd) stress in plants, reactive oxygen species (ROS) are produced, which stimulate antioxidant defense systems [5,6]. Antioxidants like catalase (CAT), ascorbate peroxidase (APX), superoxide dismutase (SOD), and peroxidase (POD) detoxified the adverse effects of reactive oxygen species in wheat grown under Cd-contaminated soil [7]. Antioxidant enzymatic processes were reduced due to cadmium (Cd) toxicity in wheat crops [8]. The accumulation of Cd in plant cells impairs the plant’s physiological and metabolic processes due to the possibility of imbalance in nutrient uptake, interrupting energy production [11]
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