| Land is such a valuable natural resource on which humankind depends to live that much attention has always been paid to it.Saline-alkali soil,accounting for about 25%of gross terrestrial area,is widely distributed in the world.The total area of various types of saline-alkali soil in china reaches about more than 33000 thousands hm2.The primary problem which requires immediately solution is how to develop it with efficient way.Ulmus pumila L,an indigenous tree species in China,has been cultivated in alkali lands as a forest planting tree species for a long time in history because of its resistance to drought,extreme temperature,and alkali.Ulmus pumila L has many variants,but by now the differences of its qualities and resistance to adverse environments among the variants have not been closely studied and certain conclusions have not been obtained.So it is not in favor of selecting superior strains of Ulmus pumila L.Based on prophase selecting of a number of Ulmus pumila L clones,our study conducted tissue culture and salinity-alkalinity screening tests for 12 Ulmus pumila L clones which showed larger growth and good adaptability in order to select superior alkali-resistance Ulmus pumila L clones.The optimum culture medium for Ulmus pumila L clones have been tested by the means of culture tissue in lab.The results showed that the growth and propagate coefficient of 4 Ulmus pumila L clones cultivated with pp culture medium added adequate hormone such as 6-BA0.2mg/L+ KT0.1 mg/L are better than that of the medium mainly composed of ms、wpm、dkw.We finally found that the best medium for Ulmus pumila L was PP+BA0.2mg·L-1+KT0.1 mg·L-1+S3%.By the means of simulating field experiments,the growth of seedlings of 12 Ulmus pumila L clones in the condition of various types of alkali such as chlorate,carbonate,sulphate,and sodium chloride with 20 different gradient concentrations had been measured.We also compared the resistant capability of single bud and bud lump of 12 Ulmus pumila L clones to saline-alkali.Experimental results showed:①the growth of 75%Ulmus pumila L clones bud lumps at the low different salt concentrations was more than the controls.Most of them grew well at the 3‰-4‰ concentration of chlorate and 6‰-8‰ of sulphate.At the same concentrations,they showed worse growth in soils containing sodium chloride and difficult to grow when concentration of sulphate was more than 1‰;various growths of No.58 Ulmus pumila L clones was superior to others and showed stronger resistances to alkali.②most individual plant of Ulmus pumila L clones grew well at the 3‰-4‰ concentration of chlorate and 6‰-8‰ of sulphate;At the same concentrations,they showed worse growth in soils containing sodium chloride and difficult to grow when concentration of sulphate was more than 1‰;various growths of No.58 Ulmus pumila L clones was superior to others and showed stronger resistances to alkali.Using simulating field experiment in lab,we studied the morphologic symptoms of 12 Ulmus pumila L clones at different types of salts with gradient concentrations.Experimental showed that the No.58 Ulmus pumila L clones manifested stronger vitality than others when it is stressed by 4 types of salts;No.20 Ulmus pumila L clones grew well at low concentrations of 4 types of salts and only inferior to the No.58 Ulmus pumila L clones at high concentrations gradient;the No.51,No.286,and No.65225 Ulmus pumila L clones grew well at low concentrations of 4 types of salts,but had dried-up in branches,crimp in leaves,and etiolation at high concentrations.By means of cluster analysis,PCA with morphologic assessment and PCA with synthetic data,it proved that No.58 Ulmus pumila L clones was the best one in resistance to saline-alkali.In conclusion,our study proved that Pp+6-BA(0.2mg/L)+KT(0.1 mg/L)+S(3%)was the best medium for Ulmus pumila L propagation which could be widely used in the industrial seedling growing for high quality Ulmus pumila L clones;No.58 Ulmus pumila L clones had higher growth at the condition of 4 types of salts with high concentrations.Bud lump of No.46 and No.51 Ulmus pumila L clones had higher growth in the soil containing chlorate.No.30 and No.41 Ulmus pumila L clones had higher growth at low concentration of salts.No.286 and No.65225 Ulmus pumila L clones had higher growth at low concentration of different salts;the value of morphological index of No.58 Ulmus pumila L clones was the largest and No.51,No.286 and No.65225 Ulmus pumila L clones took the second place.They all showed stronger resistances to alkali;among all of Ulmus pumila L clones,No.58 showed the highest quality to resist alkali and will be one of potential varieties for afforestation in saline-alkali lands. |
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