[Impact of high salt stress on Apocynum venetum growth and ionic homeostasis]

A pot experiment was conducted in a net room to study the growth responses and related mechanisms of Apocynum venetum treated with different concentrations (100-400 mmol x L(-1)) of NaCl for 30 days. The biomass accumulation, growth rate, root vigor, salt ion content and mineral ion uptake and distribution were measured. Compared with the control, treatment 100 mmol x L(-1) NaCl had lesser effects on the plant dry mass, but decreased the plant fresh mass and growth rate significantly. With increasing NaCl concentration in the medium, the plant dry mass, fresh mass, and growth rate all decreased significantly. The plant root vigor was obviously higher under 100 and 200 mmol x L(-1) NaCl stress, but decreased significantly under 300-400 mmol x L(-1) NaCl stress. With the increase of NaCl concentration in the medium, the Na+ content in A. venetum roots, stems and leaves increased gradually while the K+ content had a slow decrease, the Ca2+ and Mg2+ contents in leaves decreased obviously, and the Ca2+ content in stems and the Mg2+ content in roots increased in different degree. Under NaCl stress, the K+ /Na+, Ca2+/Na+, and Mg2+/Na+ ratios in roots, stems, and leaves decreased markedly, while the selective absorption and transportation of K+ and Ca2+ increased significantly. The stronger ability of salt exclusion and the higher selective absorption and transportation of K+ and Ca2+ were the key adaptive mechanisms of high salt-tolerance of A. venetum.