Effects Of Cadmium Stress On Mineral Elements Accumulation And Water Metabolism In Rice

Water mediates the transport of cadmium and mineral elements from roots to the shoots.The uptake of cadmium by plants can lead to unbalanced absorption of nutrients,disturbing water balance,affecting photosynthesis,and even leading to the death of plant in severe cases.Abiotic stresses such as heavy metals can cause water imbalance in plant cells,and aquaporins play an important role in controlling water transport,metal ion transport,and stress resistance.In this study,four rice varieties were used as experimental materials to study the effect of Cd on the growth of different genotypes of rice through hydroponic culture.The effects of Cd on the absorption and accumulation of other mineral elements in plants,the absorption and translocation of Cd in plants,the relationship between accumulation mechanism and water use were studied.The results are as follows:1.The absorption and accumulation of cadmium in rice have differences among varieties.When Cd was treated for 15 days,the Indica rice cultivar ANZ1 exhibited low Cd accumulation characteristics.Cd treatment for 30 days showed low Cd accumulation characteristics for Indica rice cultivar ANZ1 and Japonica rice variety B814.Indica rice ZH479 and Japonica rice variety R9475 exhibited low Cd accumulation characteristics.The uptake and accumulation of cadmium in rice also differed among different organs of plants,manifested as: root> aboveground.2.Cd will have a certain inhibitory effect on rice plants when it was Cd treatment for 15 days or Cd treatment for 30 days,manifested as plant height,dry matter weight decreased,and the degree of inhibition exists between varieties.3.Cadmium affects rice’s absorption and utilization of mineral elements.Whether it was Cd treatment for 15 days or Cd treatment for 30 days,the contents of S and Mn in shoots and roots of rice increased significantly,and the contents of Zn,Fe,and Cu decreased significantly.The content of Fe and Cu in roots were higher than that in the shoots,while the contents of roots Zn,Ca,Mg,Mn,P,and S were lower than those in the shoots.4.The expression of OsNramp1,OsIRT1,and OsHMA3 genes in roots were up-regulated by Cd treatment,indicating that OsNramp1,OsIRT1,and OsHMA3 were induced by Cd.5.The chlorophyll content,leaf area,and photosynthetic coefficients(Pn,Gs,Ci,Tr)of rice leaves were significantly reduced under Cd treatment for 30 days,indicating that cadmium treatment was suppressed to rice photosynthesis.6.The water consumption of the four rice varieties increased under Cd treatment for 30 days,the water consumption was higher in high-Cd-accumulated cultivars than the low Cd-accumulated cultivars.7.The expression levels of OsPIP1;2,OsPIP2;2,OsPIP2;5,and OsPIP2;6 genes were down-regulated under Cd stress,indicating that Cd stress may affect the absorption of water in root systems via aquaporins.