MICROBIAL COLONIZATION OF THE SURFACE OF ROOTS AT THE EARLY STAGES OFPLANT-GROWTH

The inoculation method and light and scanning electron microscopy were employed to study the bacterial and fungal colonization of the rhizop lane during the early growth stages of tomatoes, cucumbers, onions, ba rley, and blue millet. To study the microbiota composition and make di rect microscopic observations, a technique was designed for growing pl ants in nylon gauze, which makes it possible to obtain a root surface unshielded by soil particles. The extent of the rhizoplane colonizatio n by bacteria was shown to be higher than that by saprotrophic mycelia l micromycetes. On average, the projective bacterial coverage of the b asal root zone and the zone of root hairs was 0.2-2%. Virtually no mic robial cells were revealed on the root tip. The maximal bacterial colo nization of the root surface (2-9%) was observed in the basal portion of roots, very close to the seed-root juncture. During the first weeks of plant growth, microbial associations characteristic of the rhizopl ane were formed; they included a group of species common to different plants and species specific for particular plants. We identified certa in micromycete species which predominantly colonize the apical root zo ne.