Response Of Narrow Crown Black Poplar And Narrow Crown Black-Cathay Poplar To Salt Stress

Narrow crown black poplar No 2 (Populus ×zhaiguanheiyang No.2, short form L2), narrow crown black-cathay poplar No 31 (short form Lu31) and Zhonglin-46 (P. ×euramericana cv. 'Zhonglin-46', short form Z46), the three poplar varieties were cultured in the basal solution of 1/10 Hoagland nutrient solution, and were treated respectively under 5 stress gradients from 0 mmol·L^-1 NaCl to 160 mmol·L^-1 NaCl. The indexes, such as morphological indexes, photosynthesis, fluorescence parameters, and the contents of Na⁺, K⁺, Ca²⁺, protein, chlorophyll, MDA, Proline, and SOD activities, were measured to study the response of these varieties to salt stress. Z46 appeared injury symptom earlier and more seriously than the two narrow cown poplar varieties, under salt stress. Lu31 showed good ability of saline tolerance. The content of Na⁺ in roots, stems and leaves for the three varieties increased with the reinforce of salt stress, and descended in roots under heavy salt stress because of some of roots died. The content of K⁺ in roots, stems and leaves decreased with the reinforce of salt stress. Whereas the scope of K⁺ decreasing was less than that of Na⁺ increasing, which indicated that poplar had the characteristic of K-Na selective absorption and selective transportation. The content of Ca²⁺ in roots, stems and leaves changed less than Na⁺ and Ca²⁺, indicating that salt stress hardly affected the calcium pool in poplar cells. The content of MDA in roots and leaves of the three varieties increased under salt stress, as well as the membrane permeability. This indicated that protoplasm membranes were injured by salt stress. The SOD activity in roots and leaves of the two narrow crown poplar varieties increased under light and middle salt stress, whereas decreased under heavy salt stress. While the SOD activity of poplar Zhonglin-46 decreased under all NaCl treatments. This reflected that Lu31 and L2 could tolerate heavier salt stress than poplar Zhonglin-46. The proline content increased or decreased under salt stress. That was...