| The increase of population and decline of the productivity of forestry are aggravating the supply-demand situation of wood.It is well solved by means of cultivating fast-growing and high-yield plantations. But cultivating pure forest for many years ,especially coniferous forest, lead to decline of productivity of soil and degradation of the physicochemical properties of soil, threatening the sustainable operation of woodland. Acacia. is typically heliophilous species, with a short growth circle. Its root nodule can improve the soil conditions and soil fertility with a great economic, social and ecological benefit.It is convenient to cultivate large acreage plantation of Acacia .for Fujian province large parts of which lie in the southern subtropical zone.It has not been investigated whether there are strains of rhizobia which are matched with the Acacia . because it is introduced lately.In the study, 32 strains of rhizobia were isolated and purified from over ten of the Acacia .,such as A.crassicarpa, A.mangium, A.continma, A.podalyriifolia and so on, from Fuzhou, Quanzhou and Zhangzhou, Fujian province. Based on the analysis of its physiological biochemical characteristic, stress resistance, ability of infection and nodulation,and effect of inoculation, the super strains were screened which have wider rang of adaption for growth environments,power ability of infection and nodulation,and of nitrogen fixation,and which can adapt special environments,so as to support decision making in cultivating fast-growing and high-yielding timber forests of Acacia. and sustainable development of forestry. The result shows that:1．The root nodules collected from roots of Acacia. such as A.crassicarpa, A.mangium,present various shape,such as round shape, elliptoid shape,shape of cone,and so on; meanwhile it appear pink appearance,or yellow appearance. This proves a wide variation of phenotype of root nodules at varying sites in Fujian province where Acacia. were introduced.2．The colony that grows from the isolated strains in YMA culture medium plate is round, transparent or subtransparent milkiness, mucoidal, bossed in surface, regular in border, lustrous, Gram-negative, with typically individual morphology and colony property of rhizobium.3．The physiological feature was measured on Acacia. rhizobium.The result shows that in the beef-extract peptone experiment, all strains fail to grow well or not grow. In the utilization of citrate experiment, all strains can use citrate. In the utilization of carbon source experime nt, except tiny amounts of strain ,the other strains can utilize xylose, galactose, fructose, dextrose and maltose as carbon source to varying extent,and there is discrepancy among them.It shows that there are great variety of Acacia.. rhizobia in where Acacia. were introduced in Fujian province.4．According to the measurement on biochemical characters of Acacia. rhizobium, it shows that all strains in 3-keto lactose experiment are in negative reactions, proving that the isolated have not the ability of oxidizing lactose. In B.T.B reaction experiments, except that the three strains of MZ01,MZ05 and TW02 produce alkali, the others all produce acid. There are 14 strains producing alkali and 18 ones producing acid in litmus milk experiment. In gelatin hydrolization experiment, there are 23 strains liquifying the gelatin, but the others not, there is discrepancy among them.It shows that there are great variety of Acacia, rhizobia in where Acacia. were introduced in Fujian province.5．Screening tests on the stress resistance for Acacia . rhizobium were done in the study. According to temperature gradient screening test, the temperature most favorable to growth of strains is between 18℃and 32℃,and all of strains can grow at the temperature ranging from 12℃～32℃,but there is discrepancy among them. 10 strains of HJ04,HJ06,ZG01 etc can tolerate the low temperature of 8℃, and 6 strains of HJ04,LZJ01 etc still grows well at the temperature of 39℃, which are typical high-temperature resistant ones. In acidity and alkalinity gradient screening test, except 8 strains of HJ05,MZ03, all the other can grow within the acidity alkalinity scope of pH 4～9, among which the strains of ZZ02和LZJ01 can grow well at pH4 with a stronger acid resistance. In the screening test of salin e tolerance gradient, except 3 strains of MZ04,JJ03和WJ01, the other can grow under the NaCl(%) concentration less than 2．5 ,of which, 3 strains of MZ04,JJ03和WJ01 have stronger saline tolerance.Through a general comparison and analysis, super strains of Acacia. rhizobia,3strains of HJ04,LZJ01 and HM01 which grow well under the conditions of low temperature, high acidity and high NaCl concentration(%), were initially selected.6．According to the infection nodulation screening test for Acacia(?) rhizobium, inoculation with rhizobia significantly improve the figure of single nodule weight, nodulation amounts of single seedling ,nodule weight of single seedling and nodulation rate,and effect of inoculation is visible.Three month later,the results show that inoculated seedling's average nodulation amounts of single seedling were 8．1 while average nodule weight of single seedling 25．7 mg, average single nodule weight 3mg, average nodulation rate 88．75%,which were more than the control group.Through a general comparison and analysis,the strain of HJ03 have a stronger infection performance,besides strains of MZ06,HJ01,DH01,MZ03,DH02 and ZZ01．7．According to the inoculation effect test for Acacia(?) rhizobium, inoculation with rhizobia can obviously promote the growth of seedlings of A. mangium with apparent inoculation effect variation for different rhizobium strains. The results show that inoculated seedling's average seedling height growth was 8．1 cm,and average biomass of single seedling was 250mg, average chlorophyⅡcontents of leaf of seedlings of A. mangium was 1．107mg, average nodulation amounts of single seedling 6．9, average nodule weight of single seedling 15．4 mg, average single nodule weight 2．3mg, average nodulation rate 77．5%, which were more than the control group. Through a general comparison and analysis,the strains of MZ02,WJ02 and BJ01 have a excellent performance on the effect of inoculation.8．According to the impact test for inoculation effect of seedlings of A. mangium by leaching solution from winter cereal, differences of average nodulation amounts of single seedling and average nodule weight of single seedling of seedlings of A. mangium between Which was treated by leaching solution from winter cereal and which not did not reach remarkable level. |
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