The aim of this study was to determine the effect of different zinc and iron concentrations in culture
medium on growth and development of maize and wheat seedlings in terms of their inoculation with bacteria of
Azospirillum genus. Maize and wheat in vitro cultures were inoculated, respectively, by strains of Azospirillum
lipoferum and Azospirillum brasilense strains. The experimental factor was the supplementation of the culture
medium with zinc (25, 200 and 600 mg·kg-1 of the medium) and iron (25, 200 and 600 mg·kg-1 of the medium).
Counts of bacteria from the Azospirillum genus were analysed and plant seedling growth and development as
well as the content of chlorophyll in plant leaf blades were monitored.
Zinc turned out to reduce strongly numbers of bacteria of the Azospirillum genus. Azospirillum brasilense
turned out to be particularly sensitive to elevated levels of this chemical element in the environment. The negative influence of increased quantities of zinc on cereal seedlings became apparent only after the application of
the highest concentrations of this metal in the medium (600 mg·kg-1), while quantities which did not exceed
200 mg·kg-1 exerted a stimulation effect on the mass of maize and wheat seedlings.
Iron added to the culture medium in quantities which did not exceed 200 mg·kg-1 did not reduce numbers of
bacteria of the Azospirillum genus; on the contrary, they stimulated their growth. However, at higher concentrations, this metal turned out to exert a strong negative impact on the chlorophyll content in leaf blades as well as
on the mass of maize and wheat seedlings.
The inoculation with bacteria of the Azospirillum genus exerted a positive influence on the mass increase of
maize and wheat seedlings and increased chlorophyll concentrations in leaf blades. At the same time, it contributed significantly to limiting or even levelling out the toxic impact of zinc and iron during the initial phases of
plant growth and development.
The aim of the performed experiments was to analyse relationships occurring between endophytic
bacteria from the Herbaspirillum genus and Sinorhizobium meliloti Bp nodule bacteria and to examine the
condition of plants subjected to coinoculation with the above-mentioned strains in in vitro conditions. In experiments examining the impact of Herbaspirillum frisingense on Sinorhizobium meliloti BP, the stimulation of
growth of inoculated bacteria from the Sinorhizobium genus was recorded in all three combinations (48-hour
culturing, sediment and supernatant). On the other hand, the examination of interactions between the Sinorhizobium meliloti strain and Herbaspirillum frisingense strain revealed that in the case of culture and supernatant, an
antagonistic action was recorded. Besides, it was found that such coinoculation exerted a beneficial influence on
the process of seed lucerne symbiosis and yielding as confirmed by increased numbers of root nodules, higher
nitrogenase activity and greater plant mass.