Effect of salinity, gibberellic acid and Azospirillum inoculation on growth and nitrogen uptake of Zea mays

Abstract

Pot experiments were conducted to evaluate the possible interaction of salinity (osmotic potential -0.3, -0.9 and -1.2 MPa) and occurrence of Azospirillum lipoferum or exogenous gibberellic acid (GA3) (100 μg g-1) on growth and some physiological parameters of maize. 15N-uptake as well as the percentage of nitrogen derived from 15N-fertilizer were decreased by increasing the NaCl concentrations and completely inhibited at concentrations corresponding to osmotic potentials -0.9 and -1.2 MPa. The percentage of nitrogen originating from N2 fixation was significantly correlated to the total counts of Azospirillum cells that colonized the histosphere. At high NaCl concentrations although no significant changes in N % in shoot dry mass either in inoculated or uninoculated plants were observed, the total N-yield [mg(N) pot-1] was decreased. Fresh and dry shoot mass significantly increased by Azospirillum inoculation. Azospirillum and GA3 treatments were positively correlated with most of the parameters analysed. Azospirillum inoculation or GA3 application at NaCl concentrations up to -1.2 MPa significantly increased the chlorophyll, K, Ca, soluble saccharides and protein contents as compared with control plants.