Effects of plant-growth-promoting bacteria on growth and yield of pepper under limited nitrogen supply

Abstract

The influence of plant-growth-promoting bacteria (Azospirillum brasilense and Pantoea dispersa) on sweet pepper plants (Capsicum annuum L.) under limited N supply was studied. Inoculation did not affect leaf CO2 assimilation, Ci/Ca (the ratio of the intercellular to the ambient CO2 concentration), concentration of chlorophylls, chlorophyll fluorescence (maximum quantum efficiency of PSII) or SPAD readings. Total plant dry weight was significantly reduced in both inoculated and non-inoculated plants when the N supply was reduced from 12 (control) to 7 mM, whilst the NO3− and total-N concentrations in the leaves were not significantly affected by inoculation. Inoculation did not affect marketable fruit yield or the pigments (chlorophylls, lycopene and β-carotene) and carbohydrate (sucrose, glucose and fructose) contents in the fruits but flavonoids and anthocyanins were increased significantly by the addition of the bacteria, relative to non-inoculated plants under limited N supply. Key words: Plant-growth-promoting bacteria, Capsicum annuum L., soilless, photosynthesis, chlorophylls, flavonoids