Authors:Wu Xiaoli; Gu xiaoping
Abstract:Acetylene reduction activities of several bamboo species root have been investigated and determined. It is shown that with N2-backlling method, the maximum activity of two kinds of monopodia bamboo (Phyllostachys heterocycla va. Pubescens, Phyllostachys meyeri McClure) can reach 3.9 and 2.1 nmol C2H4 g¡1 dry root h¡1 respectively; with the direct determining method, the maximum activities of four kinds of sympodia bamboo (Dendrocalamus lati orus Munro, Dendrocalamopsis beecheyana (Munro) Keng f., Bambusa textilis McClure and Bambusa chungii McClure) can reach 20.5, 24.8, 10.8, 7.5 nmol C2H4 g¡1 dry root h¡1 respectively. When tested by enrichment culture method, for Ph. Pubescens and Ph. Meyeri, the maximum activities are 184 and 160 nmol C2H4 g¡1 fresh root h¡1; for D. latiorus, D. beecheyana, B. textiles and B. chungii species, the maximum activities are 978, 2743, 915, 397 nmol C2H4 g¡1 fresh root h¡1 respectively. The number of azotobacteria of four bamboo species at different rhizosphere position has been determined. It is shown that from non-rhizosphere soil to rhizosphere soil to root surface to root region the numbers of azotobacter increase sharply, and the rhizosphere effects of azotobacter are very obvious. Identi cation has been done to azotobacteria isolated from Ph. Pubescens and Ph. Meyeri. It is shown that in Ph. Pubescens rhizosphere, the azoterbacteria mainly belong to Bacillus polymyxa and Bacillus licheniformis. In Ph. Meyeri rhizosphere, it is Klebsiella pneumoniae. Using these strains(Nos 2, 12, 14, 7) to inoculating Ph. Pubescensseedlings and D. lati orus tissue culture plantlets, it is shown that inoculating associated nitrogen-xing bacteria can promote the growth of the plantlets.
Keywords:Soil fertility; azotobacter.