Studies on Relative Ion Content and Distribution in Broussonetia papyrifera Under NaCl Stress by Energy Spectrum Analysis

Ion relative content and distribution feature in the roots, stems and leaves of Broussonetia papyrifera plantlets under salt stress were analyzed with ESEM and Xray EDS. The results showed that the relative contents of Na+ and Cl- in the above three different organs of B. papyrifera under salt stress were significantly higher, while the relative contents of K+, Ca2+ and Mg2+ were lower than those in the control. With an increase of the salt concentration, the relative contents of Na+ and Cl- significantly increased both in the cortex and pith cells of the roots. Whereas the Na+ and Cl- were mainly accumulated in the stem epidermis cells, and the content of these two types of ions in the stem cortex cells was comparatively low. In addition, the contents of Na+ and Cl- were higher in the epidermis cells than those in the palisade tissue and spongy parenchyma of the leaves. The relative content of Ca2+ in the above ground part of the seedlings was significantly higher than that in the root system with the salt concentration increment in the treatment solution. Under the NaCl salt stress, the relative content of K+ declined with varied amplitude in different organs of the B. papyrifera seedlings, i.e., it dropped obviously in the roots and stems, but it did not change significantly in the leaves. At the tissue level, the relative K+ content increased in the palisade tissue and in the spongy parenchyma tissue along with the salt stress increment. Salt stress had little effect on the P3+ content in the experiment, because it was mainly distributed in the root system.