Absorption Evaluation Of Total Nitrogen And Mineral Elements Among Four Citrus Rootstocks Under Pot Culture

In the study, characterics of total nitrogen and mineral element absorption were investigated among four citrus rootstocks under pot culture:red tangerine, Citrus junos, trifoliate orange and Carrizo citrange. The main results in the present study are as follows:1. Under normal environmental conditions, the accumulation of each nutritional element varied in rootstocks, as well as in their different tissues. In the root of four rootstocks, trifoliate orange has the highest contents of nitrogen (N), phosphorus (P), potassium (K) and zinc (Zn) while red tangerine has the highest manganese (Mn) content and Citrus junos has the highest contents of magnesium (Mg) and iron (Fe); in the stem, red tangerine has the highest contents of P, K, Mg and calcium (Ca) while Citrus junos has the highest contents of Mg, Fe and Zn, and trifoliate orange has the highest contents of N, Mn and boron (B); in the leaf, red tangerine has the highest contents of P, Ca, Mg and B while Citrus junos has the highest contents of Mn and Zn, and trifoliate orange has the highest contents of N, K and Fe. On the other hand, each nutritional element varied in the distribution in different rootstock tissues. For example among the three tissues of root, stem and leaf, the stem has the highest Mg content, the second is in the leaf and the third is in the root; contents of Fe, Mn and aluminum (Al) is higher in the root than those in stem or in leaf while contents of Ca and Mg in the root is lower than those in stem or in leaf. Moreover, the order of Ca content in tissues of red tangerine or Citrus junos is stem, leaf and root while in tissues of Carrizo citrange is leaf, stem and root; the order of K content in tissues of red tangerine or Citrus junos is stem, root and leaf while in tissues of trifoliate orange is root, leaf and stem, and in tissues of Carrizo citrange is root or stem and leaf.2. Drought stress affected the absorption and distribution of each nutritional element in four citrus rootstocks, which changed as drought stress extended. For example,20-day drought stress increased N absorption in the root of Carrizo citrange. However, after40days of drought stress, there was no obvious difference in the N contents in the Carrizo citrange roots between treatment and control. Moreover,20-day drought stress decreased K absorption in the roots of red tangerine, Citrus junos and trifoliate orange. At40days after drought stress, the root K content of trifoliate orange in the treatment was still significantly lower than that in the control while as for red tangerine, the root K content in the treatment is similar as that in the control, and the root K contentof Citrus junos in the treatment is obviously higher than that in the control. Drought stress had no effect on K absorption in the root of Carrizo citrang.