Stress effect of NaCl and Na_2CO_3 on medlar (Lycium bararum L.) seedlings

Five-month old seedlings of medlar were treated with 0.3%~0.9% solutions of neutral salt (NaCl) or basic salt (Na_2CO_3) to observe their tolerant extent to salt and alkali. The results showed that the maximum stress value that medlar seedlinos could tolerate was 0.3% for the basic salt and 0.9% for the neutral salt. Under both stress conditions, the variation trend of relative growth rate, O_2~(-·), H_2O_2, MDA content and membrane permeability was similar. However, under Na_2CO_3 stress, the relative growth rate was decreased more significantly, and the O_2~(-·), H_2O_2, MDA content and membrane permeability were increased more than remarkably were than that under NaCl stress. The chlorophyll, soluble protein, soluble sugar and starch content were also evidently reduced. But under NaCl stress, there was some increase of soluble sugar in the leaves and starch in the roots. The difference of stress effect between NaCl and Na_2CO_3 was obvious, which indicated that the tolerance of medlar to saline stress was higher than to alkaline stress.