Study on associated nitrogen fixation of bamboo plants rhizosphere

Abstract

Acetylene reduction activities of several bamboo species root have been investigated and determined. It is shown that with N 2 -backfilling 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 C 2 H 4 g -1 dry root h -1 respectively; with the direct determining method, the maximum activities of four kinds of sympodia bamboo ( Dendrocalamus latiflorus Munro , Dendrocalamopsis beecheyana (Munro) Keng f., Bambusa textilis McClure and Bambusa chungii McClure ) can reach 20.5, 24.8, 10.8, 7.5 nmol C 2 H 4 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 C 2 H 4 g -1 fresh root h -1 ; for D. latiflorus, D. beecheyana, B. textiles and B. chungii species, the maximum activities are 978, 2743, 915, 397 nmol C 2 H 4 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. Identification 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. pubescens seedlings and D. latiflorus tissue culture plantlets, it is shown that inoculating associated nitrogen-fixing bacteria can promote the growth of the plantlets.