Physiological Responses Of Kochia Sieversiana And Effects Of Root On Rhizosphere Environment During Adaptation To Mixed Salt-alkaline Stress

The salinization of soil has already become an important environmental problem limiting the agricultural productivity. Songnen plain in the western of Jilin province is one of the three major regions of soda salt-alkalinized soil in the world. In this region, salinization and alkalization frequently occurred, the salt component in soil is also very complex. However, Kochia sieversiana (Pall.) C.A.M., a natural alkali-resistant plant, can survive in the region. Therefore, K. sieversiana was chosen as the test organism for this experiment. In this article, we probed the effects of root system activities on rhizosphere environment to provide the theoretical basis for the ecological recovery of salt-alkalinized grassland and the development of natural genetic resource of alkali resistant plant species.According to the features of salt-alkalinized soil in the western Jilin province, 25 salt-alkali conditions with different salinities and pHs were established by mixing NaCl, Na2SO4, NaHCO3 and Na2CO3, in various proportions. K. sieversiana seedlings were treated under these salt-alkaline mixed conditions. We consecutively detected the electric conductance and pH outside roots to analysis the effects of the root system activity on rhizosphere environment. We also determined root secretion, RGR, the contents of chlorophyll, inorganic ions and organic solutes, in order to explore the physiological response of K. sieversiana to mixed salt-alkaline stress.The results showed that the pH and salinity of 25 stress conditions were 6.35-10.62 and 60-300 mM, respectively, and that the root system activity affected mightily rhizosphere environment and regulated rhizosphere pH. The 25 stress treatments all showed that, with increasing stress time, the rhizosphere environment pH gradually move to about 8. The regulatory speed decreased with increasing salinity or stress time, which may be due to the increasing regulatory difficulty. This experiment demonstrated that K. sieversiana has a self-regulating capacity to change rhizospherere environment pH to optimum pH by the root system activity. This may be one of the reasons that K. sieversiana can adapt its salt-alkaline habitat.