A MICROBIOLOGICAL STUDY OF RHIZOSPHERE OF POPLAR

The total number of micro-organisms (bacteria and actinomycetes) in the rhizosphere of poplar reaches 16. 106 propagules per gram of dry soil and the length of mycelia averages 7 m per g of dry soil. A less active microflora occurs in the rhizospheres of young plantings (Site E). The rhizospheres of the oldest (Site A) or mycorrhized (Site B) trees are colonized by very efficient micro-organisms. The percentage of Pseudomonas falls as the poplars age. The rhizosphere of poplars is very selective to the actionmycetes. Only species with straight sporophores occur in Site A. Most of the fungal strains remain sterile. The activity of the rhizosphere micropopulation and the growth of poplars are enhanced by mycorrhiza. © 1969 Martinus Nijhoff.