Adaptation Mechanism Research Of Syntrichia Caninervis Under Salt Stress

There is large area of soil salinization in Xingjiang province. Salinization could produce serious consequences like land desertification, soil degraded and effect for the sustainable development of Xingjiang oasis. Therefore, research on plants grown in saline soil can make important practical significance to improve the saline-alkali land and ecological environment.This article made the Syntrichia caninervis in Gurbantunggut Desert as research object. We had study the changes of physical activity such as cell ultrastructure,photosynthetic pigment, photosynthetic physiological characteristics, osmotic regulation substances and antioxidant of Syntrichia caninervis under different salt concentrations and different days, to explore the salt tolerance mechanism of Syntrichia caninervis. Specific research results showed that:(1) In the concentration of less than 200mmol/L, cell ultrastructure of Syntrichia caninervis didn’t change, and returned to normal, cell wall integrity and cell membrane were clear, chloroplast structure was normal and integrated, the nucleus and nuclear membrane were clearly visible; In the concentration of 200 and300mmol/L, cell wall of Syntrichia caninervis occured plasmolysis phenomenon and fuzzy, chloroplast swelling, double membrane damaged, osmiophilic gramules increased, nucleolus dispersed; In the concentration of 400 and 500mmol/L,plasmolysis phenomenon was serious, cytoplasm damage was serious, chloroplast disintegrated, casule broke completely, nucleus atrophy, nucleolus dispersed and;(2) In different concentrations and days of salt stress, chlorophyll content of Syntrichia caninervis increased at fist and then decreased. Net photosynthetic rate(Pn)of Syntrichia caninervis reduced with the increase of concentrations and days,increased first then decreased with the change of the day. Transpiration rate(Tr)maintained a high level at first, third and fifth day less than 200mmol/L, continued to fall to the lowest point; Water use efficiency(WUE) was higher than the contrast and decreased with the concentration less than 200mmol/L, WUE decreased with theincrease of salt concentrations and days;(3) Organic osmoregulation substance(soluble sugar, soluble protein and proline)appeared different changing trends in different concentrations and days. Souble sugar content increased first then decreased with the increase of salt concentrations and days;soluble protein content decreased first then increased with the increase of stress days;With the increase of stress concentrations days, proline content increased;(4) Antioxidants(superoxide dismutase(SOD), peroxidase(POD) and malondialdehyde(MDA)) content also occured differences under different concentrations and days of salt stress. MDA content showed a trend of increase,reached maximum in the seventh day; SOD content increased with the increase of concentrations and days, appeared irregular phenomenon in the forth day; POD content increased first then decreased in different stress days and higher than the contrast. In different stress concentrations, POD content increased during the first three days and increased first then decreased in the last four days;(5) This study showed that the ultrastructure of Syntrichia caninervis,physiological and biochemical indexes and photosynthetic physiological parameters had a close relationship with stress concentrations and days, also had obvious threshold response, namely showed the ability to adapt low salt concentration(<200mmol/L) and first three days. It shows that Syntrichia caninervis has strong potential ability to adapt adversity.