PROMOTION OF PLANT-GROWTH BY INOCULUM WITH AGGREGATED AND SINGLE-CELLSUSPENSIONS OF AZOSPIRILLUM-BRASILENSE CD

Azospirillum brasilense Cd was grown with either malate or fructose as the carbon source. Malate-grown cells formed aggregates, whereas thos e grown with fructose remained separate. Scanning electron microscopy revealed a larger number of fructose-grown cells adsorbed to the root surface of inoculated maize (Zea mays) plants, as compared to the numb er of malate-grown cells adsorbed under similar conditions. Inoculatio n with fructose-grown bacteria resulted in a higher significant increa se in root surface area and root and foliage dry weight of maize seedl ings, as compared to plants inoculated with malate-grown bacteria or t he controls. Inoculation of oak (Quercus ithaburansis Decaisne) seedli ngs with fructose-grown bacteria, did not significantly promote any of the above characteristics, whereas malate-grown cells at 10(7) cfu pl ant-1 significantly improved the development of oak seedlings in the f irst month after sprouting.