This paper outlines the effects of corn smut (Ustilago maydis) infection on the physiological, morphological parameters of corn (Zea mays L.). At present, resistant corn hybrids do not exist, therefore these examinations may contribute to further studies aimed at the observation of crop resistance. The experiments described in this paper were established in greenhouse conditions and maize was grown in peat and irrigated steadily.

The infection was carried out at the phenophase of 4–5 leaves of the plants, and two ml inoculum per plant was injected into the stem between the second and third nodes. Samples were taken on the seventh and eleventh days after the infection. Furthermore, to clarify the roles of plant hormones (auxin, gibberellin, cytokinin and ethylene) in protection against the pathogen, 1 ml of each hormone per plant was also injected at the same time with the infection.

The quantity of relative chlorophyll content, photosynthetic pigments (chlorophyll-a, chlorophyll-b and total carotenoids), and the rate of lipid peroxidation were analysed. Results showed the evident beneficial effects of hormonal treatments (except for ethylene) against the fungus, which were further supported by the results of the second sampling.

Observing the morphologic parameters similar results were obtained. It is important to emphasise that the inhibitory effect of the pathogen on the plant productivity was more obvious 11 days after the infection, in terms of dry weight of plants, compared to hormonal treatments.

These results contribute to further understanding of the pathogenicity of Ustilago maydis, as well as to clarify the role of plant hormones in natural physiological control and in practical applications.

Keywords: chlorophyll content, lipid peroxidation, morphologic parameters, plant hormones, Ustilago maydis,