The Research On Endogenous Rhizobium Of Alnus And The Effection Of Alnus Growth Through Inoculation Experiment

Actinorhizal Plants are a kind of important natural nitrogen-fixing resources,and they have high value in reforestation as pioneer and accompanying species.In this study,we isolated endogenous rhizobium that took root nodule of Alnus collected from Changsha Milu City in Hunan Povince for materials,researched their biological characteristics and the effection of Alnus growth through back inoculation experiment. The main conclusions are as follows:(1) Isolation of endogenous rhizobium and its physiological type and biological characteristics tests:we obtained two endogenous rhizobium of Alnus (AC0812T017, AC0812S009).Their colony morphology were very similar.The colony texture was hard,tightness,ivory-white,showed radial or heave on solid medium.And in liquid medium,the colony was white flocculent or growth around the bottom.The strains was considered preliminarily as the member of Frankia because they had the typical mycelium morphology of frankia.The results of physiological type and biological characteristics tests showed,physiological type of AC0812T017 and AC0812S009 were both Type B.the best culture condition is:tween-80 as carbon source,pH 7.0 and temperature 30℃.(2) Nitrogenase activity and growth cycle:the strains nitrogenase activity could be effect by culture time and culture temperature.The study found out the nitrogenase activity of AC0812T017 was highest when culture time was 36h and the culture temperature was 25℃.When culture time was 24h and the culture temperature was 30℃,the nitrogenase activity of AC0812T017 reached the highest. The strain growth curve showed AC0812S009 and AC0812T017 growth very slowly in the culture condition of 28℃without nitrogen source.Began growth from the 4th day,entered logarithmic growth phase after 7 to 8 days,then reached stationary phase and continuous growth 20 to 21 days,decline phase after 22 days.(3) Back inoculation experiment of endogenous rhizobium and the impact factor of inoculation effect:the back inoculation experiment result proved that strains AC0812S009 and AC0812T017 was certainly belonged to endogenous rhizobium of Alnus,and infection ability is very strong.The best inoculation method was cut-root method.This method could obtain more root nodule and the seedling growed well. The best inoculation volume was 30-60mg per seedling.The suitable height of Szechwan alnus seedling was about 20cm.(4) Influence on the seedling growth by nodulation:the result of back inoculation experiment showed,the seedling through inoculation treatment had a strong growth situation,each growth index developed a lot.But the seedling without inoculation treatment growed slowly and weaknesses apparently.So Frankia has a great application potential for promoting forest growed and vegetation restoration of barren area,and improving the soil nutrient.