Green Excellent Valley Mixed-salinity Stress Physiological Response

[Abstract] According to approximate estimate, there is 1000 million hectare land which is affected by alkali-saline in more than 100 countries of the world, and that the area of alkali-saline land is 25 percent of the total area of plantation in our country. Superabundance of salinity in the soil imperils the growth of the mass of plants, especially does more harm to croppers which have lower tolerance to salinity. As the rapid increase in population, there are more inconsistencies between the decrease in arable area and the rapid increase in population. So there is the important significance in researching into physiological and biochemical changes of the plants in alkali-saline environment and in exploiting new salt tolerant varieties. Seedlings of millet (Setaria italica (L.) Beauv.) were stressed with 20 kinds of mixed salt which were composed of NaCl, Na2SO4, NaHCO3 and Na2CO3 at various proportions and were different in salinity and alkalinity each other (the range of total salt concentration 50-150mmol/L and pH 7.12-11.03). Ten strain indexes, such as survival rate, were determined. The relationships between the all stress acting factors and each strain index were statistically analyzed.The results showed as follows. â‘  All the strain indexes were changed regularly with the increasing strength of mixed salt-alkaline stress. Survival rate, relative growth rate, water content, chlorophyll content decreased; proline content,saccharose content, soluble sugar content and MDA content increased; superoxide dismutase activity increased first then decreased, peroxidase activity increased; â‘¡ There was a combined effect of salinity and alkalinity in mixed salt-alkaline stress, and this effect was more great than either simple saline stress or alkaline stress.â‘¢ According to the changes of water content, surperoxide dismutase activity and peroxidase activity, seedlings of millet showed some adaptability to lower stress of salinity and alkalinity. Mixed salt-alkaline stress was different from simple saline stress, such as NaCl stress, or simple alkaline stress in damaging to crops .The composition of mixed salt-alkaline was more close to natural salt-alkaline soil, so that this research can contribute to improve the salt-alkaline soil.