Effects of different Zn supply rates on growth and nutrient uptake of wheat seedlings of three genotypes under the condition of solution culture

In order to find wheat genotypes with tolerance to high rates of Zn,a solution culture experiment was conducted to investigate the influence of different Zn supply rates(Zn0、Zn0.5、Zn10、Zn40 were used to represent Zn rates at 0,0.5,10,40 mg Zn/L,respectively) on growth and Zn,Mn and Fe uptake of seedling plants of three semi-winteriness winter wheat genotypes.The obtained results showed that no obvious zinc deficiency symptoms were observed in wheat plants receiving no Zn supply.At Zn0.5 level,wheat plants also grew normally. Wheat plants of all the three genotypes tested were significantly affected in a negative way at high supplying rates(Zn10 and Zn40),with tiller,growth of root and shoot being inhibited,and leaf chlorophyll SPAD values and tolerance index(especially for root parts) being reduced.However,high rates of Zn greatly increased Zn concentration and uptake in various parts of wheat plants,especially in roots.It should be pointed out that Zn concentration and uptake,as well as Zn accumulation in roots at Zn10were higher than that at Zn40.Zn and Fe stimulated each other's absorption in roots,but inhibited each other in shoots,while Zn and Mn only had antagonistic effect on each other.Under the conditions of excessive Zn supply,Xinong 979 had the highest tolerance index,translocation rate of Zn and Fe,and Mn concentration among the three genotypes.In conclusion,when Zn was supplied 5-10 times of normal rate to wheat plants,there was not obvious negative effect on growth and development of winter wheat plants.However,when Zn was supplied at 100200 or 400800 times of normal rates,the wheat plants would be harmed severely due to Zn toxicity.Xinong 979 had the largest tolerance to Zn toxicity among the three genotypes.