Promotion of plant growth by inoculum with aggregated and single cell suspensions of Azospirillum brasilense Cd

Abstract

Azospirillum brasilense Cd was grown with either malate or fructose as the carbon source. Malate-grown cells formed aggregates, whereas those 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 number of malate-grown cells adsorbed under similar conditions. Inoculation with fructose-grown bacteria resulted in a higher significant increase in root surface area and root and foliage dry weight of maize seedlings, as compared to plants inoculated with malate-grown bacteria or the controls. Inoculation of oak ( Quercus ithaburansis Decaisne) seedlings with fructose-grown bacteria, did not significantly promote any of the above characteristics, whereas malate-grown cells at 10 7 cfu plant −1 significantly improved the development of oak seedlings in the first month after sprouting.