Rhizosheath of sinai desert plants is a potential repository for associative diazotrophs

Among 42 plant species representing the flora of north Sinai, two possessed sand grain sheath encasing the roots. They are Panicum turgidum Forssk. and Stipagrostis scoporia (Trin.and Rupr.) deWinter. Rhizosheaths, compared to surrounding free sand, accommodated higher population density of microorganisms including associative diazotrophs. Isolates secured belonged to the species of Bacillus circulans, Paenib. macerans (Bacillus macerans), Enterobacter agglomerans, Agrobacterium radiobacter and Chryseomonas luteola (Pseudomonos luteola). The rhizosheath potentiatity in revegetating sand dunes and and lands, through nitrogen fixation, plant-water relationship and root continuity for nutrient uptake, are discussed. (C) 2004 Elsevier GmbH. All rights reserved.