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The effect of different rates and methods of fertilizer nitrogen application and potassium nutrition on the root nodule t'ormation of faba bean plants vat. Nadwiglafiski and on their nitrogenase activity was studied. It was found that fertilizer N depressed the nodule formation and nitrogenasc activity, but inhibitory effect of N was smaller when it was supplied to the leaves instead to the soil. Plants growing at higher K level were in a position allowing on better development of nodules and consequently higher N2 -fixation.other legume plants (Wojcieska et al. 1993, Premaratne andOertli 1994). Addition of mineral nitrogen to the culture lnedium depresses, however, the root nodule formation and symbiotic nitrogen fixation (Ruszkowska et al. 1991, Kocoti 1993, Wojcieska et al. 1993 and many others).T h e paper presents the results of the investigation on the effect of different rates and methods of N application, at two levels of potassium fertilization, on the r o o t nodule formation of faba bean var.Nadwiglafiski and on their nitrogenase activity at successive stages of plant development.

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Some experiments were performed to investigate the physiological role of copper in oat and sunflower and to recognize some effects of copper deficiency. Oat and sunflower plants were grown in pots on a peat soil under copper deficiency conditions (–Cu) or with the optimal copper supply (+Cu). In plants the following measurements were carried out: 1) the activity of ascorbic acid oxidase (AAO) and of catechol oxidase (PPO) in different plant organs and at different stages of plant development, 2) the activity and the rate of photosynthesis, 3) the activity of RuDP-carboxylase, 4) the intensity of plant respiration. The activity of AAO and of PPO, and also the rate and the activity of photosynthesis were significantly lower under conditions of copper deficiency. The activity of both discussed oxidases depended on: 1) the plant species, 2) plant organs, 3) stage of plant development. Copper deficiency caused decrease of the respiration intensity of sunflower leaves but it increased to some extent the respiration of oat tops. Obtained results are consistent with the earlier suggestion of the authors that the PPO activity in sunflower leaves could be a sensitive indicator of copper supply of the plants, farther experiments are in progress.