Effects of CaCO3 and Zn on growth and Zn uptake of five winter wheat genotypes as well as HCO_3~- concentration and pH in nutrient solution

In order to study effects of calcium carbonate(CaCO3) and zinc(Zn) supplied in the nutrient solutions on the seedling growth and zinc uptake of winter wheat,and bicarbonate concentration and pH value in nutrient solution,five winter wheat genotypes,namely S02-8,Yuanfeng 998,Zhongyu 6,Xiaoyan 22,and Xiza 1,were mix-cultivated in Hoagland nutrient solution in a greenhouse,and micronutrients were supplied by Arnon micronutrient composition except Zn,and Zn was supplied with three levels of 0,0.016,0.082 mg/L as ZnSO47H2O,and CaCO3 with four rates as 0,10,30,60 mg/L,respectively.The results showed that,on the basis of their susceptibility to Zn deficiency: S028 and Yuanfeng 998 could be classified the susceptibility-types,and Xiza 1 were non-susceptibility types.Rational supplying of Zn was favorable for the growth of wheat;Application of CaCO3 with low rates could promote the development of wheat to some extent,whereas,excessive application of CaCO3 inhibited the growth of wheat.The biomass yield and ratio of root to shoot of susceptibility wheat were significantly lower than that of non-susceptibility one.Application of CaCO3 had no significant influence on Zn uptake of wheat,but Zn uptake by roots and shoots of wheat plants increased with(increasing) Zn rates,and Zn was largely accumulated in the roots at the high rate of zinc supply;In addition,wheat plants of susceptibility types were more prone to accumulate zinc in roots than non-susceptibility wheat,and the Zn translocation rate of the former from root to shoot was much lower than that of the latter.Increased both HCO3- concentration and pH significantly with increasing rate of CaCO3 application.Under the condition of exchanging the nutrient solution with 10 day interval,the variation of nutrient pH was ranged within 0.2 pH unit during a day;however,pH of nutrient solution showed an increasing tendency with the proceeding of the cultivation and pH increased in the range of 0.79 to 2.37 within 10 days.At the end of culture,the pH differences between the treatment with various CaCO3 additions was much less pronounced than that at the beginning of culture.In addition,CaCO3 addition with high rate inhibited the growth of wheat seedlings,and exacerbated the zinc deficiency symptoms,but it did not decrease the zinc uptake rate,therefore,we could speculate that high rate of CaCO3 could decrease the physiological activity of Zn taken up in the plants through the induced high concentration of HCO3-.