Genetic Diversity Analysis Of Non-Selective Cation Channel Ion Transport Efficiency In Rice

In the areas suffering from heavy metal pollution in the south of China,there are significant different cadmium contents in rice among genotypes,regional and years,cadmium content of roots,stems,leaves and other vegetative organs also have significant differences in the genotypes.The uptake of cadmium by various organs of rice needs to be transferred and accumulated into the kernel through a variety of ways,and the non-selective cation channels(NSCCs)is one of the important ways to absorb and transport cadmium.In this paper,taking several rice genotypes as experimental objects,the genetic diversity of ion transport efficiency of non-selective cation channels in rice was analyzed.The conclusions are as follows:1.The contribution of NSCCs to the uptake and translocation of Cd2+ in rice seedlings was significantly different among genotypes.When 0.2 mmol/L La Cl3 is added to the nutrient solution,the cadmium contents of the roots and aboveground parts of 23 rice genotypes was significantly decreased,the inhibitory effect of NSCCs inhibitors on the cadmium accumulation of low accumulation rice root genotype was significantly higher than the high accumulation one.The results shows that the contribution rate of NSCCs on the cadmium accumulation of high accumulation rice root genotype was significantly lower than the low accumulation one,however,there was no significant difference in the contribution of NSCCs to the aboveground cadmium accumulation among 23 rice genotypes.2.In the environment of cadmium stress,there are significant differences in the genotypes for the cadmium accumulation of isolated rice cobs and grains,and also for cadmium transfer coefficient between them.The cadmium accumulation of rachis and grain rises with the increase of cadmium concentration(1.0?1.5?2.0 mg/L)in the treatment solution.The cadmium contents in cob between the high cadmium accumulation genotype and low cadmium accumulation genotypes have great differences,which are by 10.37 times,9.79 times and 12.14 times,respectively;the cadmium contents in grain are more than by 4.31 times,3.94 times and 11.11 times,respectively.The cob cadmium transfer coefficients of grain transport(TF)among genotypes were significantly different,the transport coefficient of No.1(hardcore Ukraine),No.8(three hundred tablets)and No.72(Nanjing 7623)are low and stable,while the transfer coefficient of No.70(IR661-1)is high and stable.3.There are remarkable difference in the rate of chlorosis of detached leaves,thecadmium accumulation and the cadmium translocation rate of NSCCs in the leaves under cadmium stress.Under the 0.1~1.0 mg/L cadmium stress for 5 days,the total chlorophyll content of the detached leaves shows a different degree of decline with the increase of Cd2+concentration.Compared with the control group,the drop of the total chlorophyll content for low accumulation genotypes are more than the high accumulation genotypes.Under the1.0~2.0 mg/L cadmium stress for 5 days,the cadmium accumulation of the detached leaves rises with the increase of Cd2+ concentration,the cadmium accumulation of the detached leaves in most of the high accumulation rice genotypes are higher than the low accumulation genotypes.NSCCs for the contribution of the accumulation of Cd in detached leaves are greatly different among different genotypes.4.In the natural environment,the cadmium contents in rice are determined by the cadmium contents of the soil,growth season,rainfall and genotype.The content of cadmium and other elements in late rice genotypes are significantly higher than that of early rice genotypes.The content of cadmium in the soil of rice roots changes with the growing season,for example,which can increase from 0.13 to 0.19 mg/kg in July to 0.85 to 1.48 mg/kg in October.The contents of Cd,K,Mg,Fe and Mn in late rice grain and cob are much higher than that of early rice.However,the contents of Ca and Zn in late rice grains are lower than those in early rice.The concentrations of some elements in cob are about 2~10 times higher than that in grain.The concentrations of Cd and the transfer rate in the cob of the low Cd accumulation genotype are lower than the high accumulation Cd genotype.There was a significant relationship between Cd and Mn content in rice grains harvested at different Cd contents.Different rainfall is the key factor for the change of Cd content in the surface soil and grain of early rice and late rice.