Study On The Differences Varieties Of Wheat Cadmium Uptake And Translocation

Heavy metals are an important pollutant in the environment and agricultural products.Compared with other heavy metal elements,cadmium is extremely mobile in the soil,and it is easy to accumulate for crops and be stored at the harvest site.Wheat is an important food crop and the most widely covered food crop in the world.Different wheat varieties have different absorption,translocation and detoxification rules for cadmium.Exploring this difference is of great significance to further adopt effective agricultural measures to reduce cadmium content in wheat grains.In this paper,the high-cadmium accumulation varieties(Bainong 160)and low-cadmium accumulation varieties(Pingan 8)obtained in the previous screening were selected to analyze the differences in cadmium absorption,translocation and cadmium detoxification mechanisms between the varieties,the result shows:(1)Hydroponic test showed that at Cd30 level,SOD,POD,CAT activity of Bainong 160 were significantly higher than Pingan 8,the MDA,H2O2 concentration of Pingan 8 was significantly higher than Bainong 160,and after cadmium stress the growth index of Pingan 8 decreased larger than Bainong 160 indicated Pingan 8 suffered a greater degree of oxidative damage and is a cadmium-sensitive variety,Bainong 160 is a cadmium-tolerant variety.(2)Under hydroponic conditions,in addition to the transport coefficient,the cadmium concentration in the shoots and roots and the cadmium accumulation of the whole plant of Bainong 160 wheat seedlings were significantly higher than that of Pingan 8,and the cadmium absorption time/concentration kinetic test also proved this conclusion.The lower cadmium absorption capacity of Pingan 8 may be related to the low expression of heavy metal transporter gene TaNramp6 and cadmium-induced programmed cell death.Compared with Pingan 8,cadmium stress induced a strong reaction in the root cells of Bainong 160,included lignin deposition,simultaneous increase of NPT and GSH,and high expression of TaHMA3 and inhibited expression of TaHMA2,these responses may collectively resulted in the roots of Bainong 160 has a stronger cadmium retention capacity and a lower migration of cadmium from the roots to to shoots.(3)Under pot conditions,the grain cadmium content of Bainong 160 was significantly higher than that of Pingan 8,and the soil cadmium in Bainong 160 was more effective,and the cadmium absorption of Bainong 160 unit mass root system was significantly higher than Pingan 8,indicated that its root system has a stronger ability to absorb cadmium.In the two-year pot experiment,under the treatment of Cd1.5 and Cd10,the total cadmium accumulation of Bainong 160 was significantly higher than that of Pingan 8,and the cadmium accumulation ratio of the two varieties reached 76%-95%during the flowering period,and there was no difference between varieties.Compared with other tissues,the cadmium distribution ratio of the two varieties in the stalk under mature stage was the largest,Bainong 160 and Pingan 8 were 30%-35%and 37%-49%,respectively.The cadmium in the grains of Bainong 160 mainly came from the redistribution of cadmium in plants(58%),and the cadmium in the grains of Pingan 8 mainly came from the absorption of cadmium after flowering(62%),which was also the reason for the difference between the two varieties.From the perspective of transshipment,there was no significant difference between the transfer coefficients of the two varieties at each node under Cd1.5 treatment.Under Cd10 treatment,the transfer ability of cadmium in Bainong 160 in the rachis and the first node was an important part of the difference in the upward transfer of cadmium between the two wheat varieties.(4)At the mature stage,the cadmium distribution ratio of the two varieties in the stalk under mature stage was the largest,Bainong 160 and Pingan 8 were 30%-35%and 37%-49%,respectively.The leaves and roots are the photosynthetic organs and nutrient absorption organs of the plant.The presence of cadmium in these parts affects the plant’s cadmium tolerance and cadmium transfer.In the first leaf,second leaf and roots,the cadmium in the cell walls and soluble fraction of Bainong 160 and Pingan 8 accounted for a large proportion,and the total was about 93%.In addition,cadmium is mainly combined with pectin or protein in the first leaf,second leaf and root cells,and the proportions reach 38%-73%and 12%-58%,respectively.Under the treatment of Cd10,the percentage of cadmium combined with insoluble phosphate in the first leaf and the second leaf of Bainong 160 was significantly higher than that of Pingan 8.This shows that the insoluble phosphate in Bainong 160 has a strong binding ability with Cd,and the complex formed by it has less fluidity and toxicity in vivo,so Bainong 160 has a stronger detoxification ability.