Effects Of Silicon On Cadmium Absorption And Translocation In Rice

In recent years,cadmium?Cd?pollution in farmland of China becomes increasingly prominent,which makes the safety of rice production attached a great deal attention.Silicon?Si?is beneficial for growth of rice.Rice seedlings can effectively accumulate Si.In our study,hydroponic experiments and field experiments were performed to study the effect of Si on the uptake and transport of Cd in plants and the mechanism of Si in improving rice tolerance to Cd stress.The main results were as follows:1.The results of hydroponic experiments indicated that Si alleviated the inhibiting effect of Cd stress on the growth of rice seedlings effectively and maintained the stability of antioxidant enzyme in the range of silicon concentrations.Under 2.7?mol·L^-11 CdCl₂ stress,the growth of rice seedlings was inhibited,the content of Malondialdehyde?MDA?was significantly increased,the content of soluble protein and the activity of Peroxidase?POD?was significantly decreased.Adding Si in Cd solution increased the activity of POD and the content of soluble protein,while decreased the content of MDA,improved the tolerance of rice seedlings to Cd stress.2.Si had significant influence on the absorption and transport of Cd,Si by rice seedlings in the range of silicon concentrations.Si concentration had no significant effect on the Cd content in roots but significantly decreased the Cd content in shoots with increasing Si concentration in the rhizosphere.The transport factor?TFs?of Cd from roots to shoots was significantly decreased while the accumulation of Si was significantly increased in roots of rice seedlings,and the transport ratio of Si from roots to shoots was significantly increased.3.The concentration of Si had significant effects on the absorption of necessary elements in rice seedlings under the cadmium stress.Si significantly increased the content of Mg,Ca,Fe and Zn in roots and the content of Zn and Fe in shoots.But Si had no significant effects on the content of K and Mn in roots,and the content of K,Mg,Ca and Mn in shoots.4.Foliar application with nano-silicon had significant influences on the absorption and accumulation of Cd in rice.Foliar application with 5.0²5.0 mmol·L^-1 nano-Si reduced Cd content in grains and rachises by 31.6%⁶4.9%and 36.1%⁶0.8%respectively.The content of Cd in flag leaves,second leaves,uppermost internodes and nodes decreased when 25 mmol·L^-1 nano-Si was supplied.Foliar application with nano-silicon had no significant effect on the Cd content in roots,stalks,second nodes and second internodes.5.Foliar application with nano-silicon had significant effects on the accumulation of K,Mg and Fe in grains and rachises of rice,but had little impact on the accumulation of Ca,Mn and Zn in grains and rachises of rice.The uppermost internodes displayed much higher K concentration than other aerial organs and second leaves under flag leaves displayed much higher Mg than other aerial organs.The content of Fe in rice roots was as high as 74.12⁷8.60 g·kg^-1,but Fe in other organs was only in the range of 0.11⁰.93 g·kg^-1.6.Spaying nano-silicon had a significant impact on the transfer of K,Mg,Fe and Cd between different organs in rice.After foliar application with nano-Si,TFs of Cd ions from the uppermost nodes to rachises significantly declined,but TFs of K,Mg,and Fe from the uppermost nodes to rachises increased significantly.High dose of nano-Si was more effective than low dose of nano-Si in reducing TFs of Cd from roots to uppermost nodes and from uppermost nodes to rachises.