Studies On The Excluding Mechanism Of Puccinellia Tenuiflora

The formation of alkaline soils has been a big problem throughout the world. Some plants can tolerate high levels of salt and their special mechanisms for tolerance are the focus of much research. Na⁺ is one of the most harmful ions causing plant salt stress. Puccinellia tenuiflora can live in high concentrations of Na⁺. Although there have been many physiological studies on the mechanisms of salt tolerance in P. tenui flora, there have been few on its tolerance to Na⁺. This study measured the amount of Na⁺ exclusion from roots and excretion from leaves of P. tenui flora and preliminarily analyzed the characteristic of roots refusing Na⁺.The plants which had grown in 25, 50 and 150 mmol·L^-1 NaCl solution were transferred into Hoagland solution without NaCl and cultured for 6 h, 12 h, 24 h, 48 h, 96 h, and 168 h,respectively. Na⁺ content of single plant was analyzed. The results showed Na⁺ content of plants which had been transferred to Hoagland solution had slightly higher Na⁺ levels than those under stress. It was sussested that has hardly excreted Na⁺ from the roots. Therefore, Na⁺ exclusion from roots is not the main way for P. tenui flora to tolerate Na⁺.Aboveground parts of P. tenui flora was washed in distilled water and the Na⁺ contents in extract solution and whole plants were analyzed. The Na⁺ content in the extract solution was significantly (P<0. 05) lower than that in the whole plant. The results showed that excretion of Na⁺ by the leaf was also not the main way that the plants tolerated Na⁺.Plants of P. tenui flora and Triticum aestivum were grown in Hoagland solution containing NaCl at concentrations of 5 mmol·L^-1, 25 mmol·L^-1, 50 mmol·L^-1, 100 mmol·L^-1, 150mmol·L^-1, and 200mmol·L^-1. Na⁺ contents were measured after 1d, 2 d, 4 d, and 7 d. The rates of Na⁺ absorption of T. aestivum were always higher than P. tenuiflora with the increase in NaCl concentration and time. However, it decreased when NaCl concentration was 200 mmol·L^-1. SA of two species increased as NaCl concentration rose , and decreased over time. SA of T. aestivum was lower than that of P. tenui flora for all treatments. So was ST of two species. These results showed that selective absorption of K⁺ and Na⁺ ability of P. tenui flora was greater than that of T. aestivum ,and the selective transportation of P. tenui flora was also better.In conclusion, the better selective absorption and transportation of K+ and Na+ may be the main path that P. tenui flora tolerances high levels of Na+in nature.