Increasing phosphate inhibits cadmium uptake in plants and promotes synthesis of amino acids in grains of rice

• Published in: Environmental pollution (1987) Vol. 257; p. 113496
• Main Authors: Zhao, Yanling, Zhang, Changbo, Wang, Changrong, Huang, Yongchun, Liu, Zhongqi
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.02.2020
• Subjects: Amino acids; Amino Acids - metabolism; Biological Transport; Cadmium; Cadmium - analysis; Cadmium - metabolism; Cadmium - toxicity; Fertilizers - analysis; Iron - analysis; Oryza - metabolism; Phosphate; Phosphates - analysis; Phosphates - chemistry; Phosphorus - metabolism; Plant Leaves - chemistry; Plant Roots - metabolism; Rice; Root iron plaque; Soil - chemistry; Soil Pollutants - analysis; Soil Pollutants - metabolism; Soil Pollutants - toxicity; Cadmium; Root iron plaque; Amino acids; Phosphate; Rice
• ISSN: 0269-7491; 1873-6424
• DOI: 10.1016/j.envpol.2019.113496

Technologies for cleaner production of rice in cadmium (Cd) contaminated field are being explored worldwide. In order to investigate the inhibition mechanism of phosphate on Cd transport in soil-plant system, controlled experiments were performed in this study. Experimental results showed that Cd levels in roots, flag leaves, rachises and grains of rice plants (Oryza sativa L.) were significantly reduced by supplement of 0.5–2.5 g kg−1 calcium magnesium phosphate fertilizer (CMP). Path coefficient analysis revealed that phosphorous had significant negative direct effect on Cd, but positive indirect effect on essential and non-essential amino acids. Applying 2.5 g kg−1 CMP made the Cd concentration decreased by 45.7% while free essential and non-essential amino acids increased by 28.0–28.6% in grains. Levels of the branched-chain amino acids in grains were much higher than other essential amino acids, and increased with the amount of CMP fertilization. After application of CMP, pH of soil solution and thickness of the iron plaque around roots increased significantly. Spectra from X-ray photoelectron spectrometer (XPS) showed that content of N, P and Fe increased apparently, C, O and Ca had no change, while S decreased by 74.2% in roots after application of 2.5 g kg−1 CMP. Meanwhile, Cd concentration in protoplasts of root cells decreased by 39.5–80.1% with the increase of CMP. These results indicate that application of CMP can effectively inhibit Cd accumulation in root protoplasts by promoting iron plaque formation on the root surface, reduce Cd concentration and increase free amino acids in rice grains. [Display omitted] •Increasing P level inhibits Cd accumulation and promotes synthesis of amino acids in rice grains.•P inhibits cadmium transport from root protoplasts to rachises of panicles.•Precipitation of Cd in vegetative organs as well as in soil is promoted by P application.•N, P and Fe in roots increased greatly but S decreased with P application. Main findings: (1) Increasing phosphate level inhibits Cd accumulation and promotes synthesis of amino acids in rice grains. (2) Precipitation of Cd in vegetative organs as well as in soil is promoted by application of phosphate fertilizer.