Do brassinosteroids and iron plaque affect the accumulation of As and Cd in rice (Oryza sativa L.)

Abstract Brassinosteroids (Brs) are a class of plant polyhydroxysteroids and play pivotal roles in plant growth and development. Furthermore, Brs are involved in the responses of plants to various heavy metal stresses. However, the role of Brs in the translocation and uptake of arsenic (As) and cadmium (Cd) in rice (Oryza sativa L.) remains largely unknown. The present study was performed to examine the impacts of 24-epibrassinolide (Br24: 10−10 and 10−8 M), 28-homobrassinolide (Br28: 10−10 and 10−8 M), FeSO 4 addition (1 g kg −1 Fe) and their interactions on the accumulation of As and Cd by rice in pot trials. The results showed that the Fe content in iron plaque was increased by Fe addition but not by Br24/Br28. The interactions of Br24/Br28 and Fe enhanced the Fe contents in roots and stems. Br24/Br28 or Fe addition decreased the translocation and accumulation of As and Cd in rice grains. The interactions of Br24/Br28 or Fe further reduced the contents of As and Cd in rice grains. The As contents in grain were reduced by 60% under Fe addition, 18%–63% under Br24, 56%–73% under Fe+Br24, and 66%–72% under Fe+Br28. The grain Cd contents were reduced by 65% under Fe addition, 33%–61% under Br24, 56%–67% under Fe+Br24, and 43%–66% under Fe+Br28. These results suggest that the application of Fe, Br24/Br28 or their combination is effective in reducing the contents of As and Cd in rice grains, which has strong implications for agricultural production and food security.