Foliar application of several reagents reduces Cd concentration in wheat grains

Mechanism of foliar application of boron to alleviate cadmium toxicity in winter wheat (Triticum aestivum L.)

Our previous work shown that boron (B) can inhibit cadmium (Cd) absorption in winter wheat, while the mechanism is not well understood. In this study, the mechanism of foliage spray B on Cd uptake in Cd-contaminated farmland was characterized with three treatments: spraying distilled water (CK), spraying 0.3% B fertilizer (F0.3%), and spraying 0.6% B fertilizer (F0.6%). The spraying treatment was conducted during the jointing stage and booting stage, respectively. The objective was to investigate the impact of different concentrations of B fertilizer application on Cd content, yield, physiological biochemical response, Cd transporter in wheat. Results showed that the yield increased with increasing B spray concentration compared with CK treatment. The wheat yield increased by 1.29%∼12.50% under foliar B application. The Cd concentration in both shoot and root of wheat seedlings were significantly decreased with foliar application of B at jointing stage and booting stage. The Cd concentrations in root and seed were also decreased with B treatment at maturity stage, especially after treatment with F0.6%, the Cd absorption in wheat grains exhibited a significant reduction of 31.20%. In addition, foliar application of B significantly increased antioxidant enzyme activities, include APX, SOD, CAT, and POD. Compared with CK, the MDA content in leaves showed a significant decrease with 30.48%-50.14%, while the GSH content showed an increase with 76.32%-1.05%. The down-regulation of the uptake and transport genes (TaNramp5, TaLCT1 and TaHMA2) and the up-regulation of compartmentalization transport genes (TaTM20 and TaHMA3) may contribute to the reduction of Cd accumulation in shoot. Overall, our results suggest that foliar spraying of B could increase B accumulation and yield, and alleviate Cd toxicity by reducing Cd uptake, enhancing the antioxidant capacity, regulating the expression of Cd genes in wheat.

Heavy Metals in Agricultural Soils: Sources, Influencing Factors, and Remediation Strategies

Soil heavy metal pollution is a global environmental challenge, posing significant threats to eco-environment, agricultural development, and human health. In recent years, advanced and effective remediation strategies for heavy metal-contaminated soils have developed rapidly, and a systematical summarization of this progress is important. In this review paper, first, the anthropogenic sources of heavy metals in agricultural soils, including atmospheric deposition, animal manure, mineral fertilizers, and pesticides, are summarized. Second, the accumulation of heavy metals in crops as influenced by the plant characteristics and soil factors is analyzed. Then, the reducing strategies, including low-metal cultivar selection/breeding, physiological blocking, water management, and soil amendment are evaluated. Finally, the phytoremediation in terms of remediation efficiency and applicability is discussed. Therefore, this review provides helpful guidance for better selection and development of the control/remediation technologies for heavy metal-contaminated agricultural soils.