A b s t r a c t. The aim of the experiment was to establish the influence of biostimulation on the sugar beet seeds. The seeds came from the specialized breeding program energ'hill or were irradiated by the laser in two doses. The impact of the biostimulation was analyzed by determining the nitrate reductase activity and the nitrate, chlorophyll and carotenoids contents in leaves, as well as, the dry matter and sugar concentration in mature roots. The field experiment was established for two sugar beet cultivars. Biostimulation by irradiation and a special seed breeding program energ'hill had a positive influence on some examined parameters (particularly on nitrate reductase activity in Ruveta and in numerous cases on photosynthetic pigments in both cultivars). Regarding the dry matter accumulation and sugar concentration this impact was more favourable for Tiziana than for Ruveta cultivar.K e y w o r d s:

A b s t r a c t. Germination and sugar beet yield after seed stimulation were investigated. The seeds came from the energ'hill technology and were subject to laser irradiation. The experiments were conducted in the laboratory and field conditions. Lengthening of germinal roots and hypocotyls was observed. A positive effect of the stimulation on the morphological features was observed for the Eh seeds and laser irradiation applied in a three-fold dose. The energ'hill seeds exhibited a significantly higher content of carotenoids in seedlings and an increase in the content of chlorophylls. Laser light irradiation favourably modified the ratio of chlorophyll a to b. The leaves and roots of plants developed from the energ'hill and irradiated seeds were characterized by higher dry matter content thanin non-stimulated seeds. Seed stimulation had a positive influence on yielding and the saccharose content.K e y w o r d s: sugar beet, seed stimulation, germination, yield

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Plants exposed to osmotic stress exhibit changes in their physiology and metabolism. In general, osmotic stress reduces water availability and causes nutritional imbalance in plants. In the present study, we compared the response of cucumber (Cucumis sativus L. var. W³adko F-1) to ionic (100 mmol·dm -3 NaCl) and osmotic stress (10% PEG 6000). Both stress factors reduced significantly fresh and dry weight of 7-day-old cucumber seedlings. Under PEG treatment reduction of cucumber dry mass was lesser than in fresh mass, whereas under salt stress decrease in dry weight of cucumber shoots was more pronounced than in fresh mass. Salt stress caused severe decrease in nitrate concentration and activity of nitrate reductase (NR). In cotyledons nitrate content declined to 17% of the control and similar reduction in NR activity was observed. In the roots, observed changes were not so drastic but there was also strong interaction between reduction in nitrate content and NR activity. Under 10% PEG both nitrate concentration and NR activity in cucumber roots were significantly higher in comparison to control plants. In cotyledons NR activity was significantly lower than in control plants, while decrease in nitrate content was not statistically significant. Phosphate concentration did not change significantly in cucumber cotyledons but increased in roots treated both NaCl (32% increase) and PEG (53% increase). Similar tendencies were observed in acid phosphatase activity. Obtained results indicated that osmotic and salt stresses evoke differential responses, particularly in growth reduction and nitrogen metabolism in cucumber seedlings.

In this study, investigated were the effects of NaCl (60 mmol·dm -3 ) and NaCl supplemented with different salts (5 mmol·dm -3 CaCl 2 , CaSO 4 , CaCO 3 , KCl), on growth of two maize varieties (Cyrkon and Limko). After 7 days of cultivation in nutrient solution the growth response to salinity of both maize varieties was similar. NaCl led to a dramatic decrease in growth of plants (approx. 50% reduction in fresh and dry weight of root, and 70% reduction in fresh weight of shoot). Addition of extra Ca 2+ or K + to nutrient solution containing NaCl did not definitely improve the growth parameters of maize. However, among the tested salts, CaCl 2 had a beneficial visual effect on maize seedlings. In other cases the plants showed noticeable symptoms of salt damage. In long term exposure to salinity (two weeks) growth of Cyrkon was more inhibited than Limko. Comparison of growth responses in short-term exposure to salinity (7 days) with long-term (14 days) showed that in Cyrkon variety the negative effects of NaCl were intensified and addition of CaCl 2 to salinized solution had not positive effects on growth. On the contrary, in Limko variety, there was a significant improvement in growth (especially in root dry weight). This fact indicates that during longer exposure to salinity Limko was able to adapt to those conditions. Salinity caused a significant decrease in leaf nitrate reductase activity (60% and 30% reduction respectively in Limko and Cyrkon). Addition of CaCl 2 to salinized nutrient solution resulted in greater enzyme inhibition in Cyrkon (50% decline in relation to plants grown under sole NaCl), and 30% increase in Limko. Inhibition of nitrate reductase activity did not cause a decrease in concentration of soluble protein in maize leaves.

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The aim of this study was to evaluate the effect of pre-sowing seed treatments on some agro-physiological parameters of sugar beets. The selected seed treatments were laser stimulation, hydropriming and a combination of hydropriming and laser irradiation. The impact of the stimulation of seeds was analysed by determining the acid phosphatase activity, concentration of phosphate and photosynthetic pigments in leaves as well as the nutrient status and some yield parameters of the roots. The plants were assayed four times during the growing period. The experiment showed that the priming methods had a relatively small effect on both the level of orthophosphate and total phosphorus concentration. On the other hand, the plants raised from seeds both hydro-and laser-primed preserved a more stable level of phosphates during the whole growing season than the other plants. The highest activity of acid phosphatase was observed in younger plants and among different seed treatment, plants grown from non-primed seeds and laser-primed seeds showed the highest enzyme activity. In later growth stages, enzyme activity lowered considerably. Considering the effect of different seed treatments, a significant increase in enzyme activity was observed in plants emerged from hydroprimed or laser stimulated seeds. In addition, an increase in chlorophylls occurred in plants emerged from hydroprimed seeds and from hydro-and laser-primed ones. Seed stimulation had a positive effect on the potassium content, particularly in leaves of sugar beet, and on some yield parameters of the roots. Concluding, the effect of pre-sowing seed stimulation (priming) was visible during the entire growing season. Out of the examined seed treatment methods, hydropriming alone or in combination with laser radiation caused the highest alterations in the assayed parameters.

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