The influence of stress factors on the plant can, on the one hand, lead to worse functioning of the plant and loss of its crop, but on the other, it can have a positive effect on the metabolism of compounds with documented biological activity. In this study, the effect of light and drought intensity on photosynthetic activity and physiological status of two barley varieties, as well as the antimicrobial, antioxidant properties and profile of polyphenolic compounds of green barley were analysed. It was shown that under the conditions of water shortage, the KWS Olof variety showed a smaller decrease in CO₂ assimilation and transpiration and higher values of these parameters at both light intensities. Only in the KWS Olof variety increased stress as a result of increased light intensity. It has also been shown that both the intensity of radiation and drought-related stress have a significant impact on the profile of polyphenolic compounds from green barley, without a simple relationship between the impact of stress factors on the content of polyphenols. Changes in the profile of polyphenolic compounds augmented the antioxidant and antimicrobial activity of the material. This, in turn, proposes the possibility of reducing the applied doses of herbal material thanks to a greater content of active substances in extracts obtained from the plants used to produce medicinal preparations.

The research was conducted during the years 2007–2013, on the base of a long-term study established in 1958, at the Experimental Station Brody (52°26′ N; 16°18′ E), belonging to the Poznań University of Life Sciences. Varieties of potatoes resistant to cyst nematodes were grown in a seven-course crop rotation (potato—spring barley—alfalfa—alfalfa—spring oilseed rape—winter wheat—winter rye) and in continuous monoculture. The presented study from the years 2007–2013 covers the next 8th rotation of the 7-field crop rotation (since 1958). With regard to continuous cultivation, this is the period between the 50th and 56th year of the potato monoculture. The experiment included 11 fertilization variants, of which the following 7 were included in the study: 1—control object without fertilization, 2—manure, 3—manure + NPK, 4—NPKCa, 5—NPK, 6—NP, 7—NK and 8—PK. Every year, mineral and organic fertilization was applied in the following doses per 1 ha: N—90 kg, P—26 kg, K—100 kg, manure—30 t and Ca—0.7 t. Potato cultivation in monoculture resulted in a significant reduction in tuber yield compared to crop rotation and a reduction in the number of tubers per plant and the average weight of one tuber. Manure fertilization, especially in combination with NPK mineral fertilizer, had a more favorable effect on the level of potato yielding and the content of N, P, K and Mg in tubers compared to only mineral fertilization, but decreased the content of dry matter, starch and Ca. The results of long-term experiment indicate that the most effective in potato cultivation is the combined application of both manure and full mineral fertilization (NPK) with the proper sequence of plants (crop rotation).

The article presents the technological and antioxidant properties of potato juice (PJ) protein concentrate obtained by the novel ultrafiltration method. Commercial products, obtained from waste PJ by the traditional method of acid coagulation of proteins, were studied for comparison. Functional properties such as water or oil absorption, foaming capacity, and foam stability (FS) as well as solubility at various pH were assessed. Moreover, the total phenolic compound content, antioxidant activity, and mineral composition were determined. The results showed that PJ protein concentrate obtained by ultrafiltration has good oil absorption properties (6.30 mL/g), which is more than two times higher than the commercial proteins used in the comparison (P2 = 2.33 mL/g and P3 = 2.67 mL/g). Moreover, the ability to create and stabilize foam was also higher (FS ranging from 20.0% at pH = 10 to 11.3% at pH = 2 after 60 min of testing). It had higher content of macro- and microelements and antioxidant activity compared to other samples. Therefore, it is possible to obtain interesting potato protein concentrate from the waste product of the starch production process, which may be an interesting raw material for enriching food.

Climate change, including decreasing rainfall, makes cultivating cereals more difficult. Drought stress reduces plant growth and most all yields. On the other hand, consumers’ interest in ancient wheat varieties, including spelt, is growing. The aim of this work is to compare the response to drought stress between spelt (Triticum aestivum ssp. spelta) and common wheat (Triticum aestivum ssp. vulgare). Six cultivars of spelt from different European countries and common wheat ‘Bogatka’ as a reference were chosen for research. The photosynthesis process, chlorophyll fluorescence, relative water content, and the content of free proline and anthocyanins in well-watered and drought-stressed plants were measured. It was shown that the spelt cultivars ‘Franckenkorn’ and ‘Badengold’ were much more resistant to water deficit than other cultivars and even common wheat. A slight reduction of CO₂ assimilation (by 27%) and no reduction of transpiration rate, with simultaneous intensive proline (eighteen times fold increase) and anthocyanins accumulation (increase by 222%) along with a slight increase in lipid peroxidation level (1.9%) revealed in ‘Franckenkorn’ prove that this cultivar can cope with drought and can be effectively cultivated in areas with limited water abundance.

To prevent the staggering degradation of the environment, restrictions in the use of plant protection products and fertilizers are being strengthened every year. Therefore, methods for improving plant tolerance to unfavorable environmental conditions are sought to positively affect both plants and the natural environment. Here, we evaluated and compared the efficacy of four commercial biostimulants on the tolerance of winter wheat to drought stress. The effects of the following biological agents: Bacillus sp., soil bacterial strains, free amino acids, and humic substances on winter wheat were assessed in a pot experiment under full hydration soil moisture and under drought. Among the studied biostimulants, the two based on bacterial strains had the strongest beneficial effects on improving the tolerance of wheat plants to drought. In plants treated with either of these two, the highest level of CO₂ assimilation was recorded under drought. Moreover, in the same plants, the decrease in transpiration value due to drought was the smallest. The highest stomatal conductance under drought was also noted in these same plants. The results of chlorophyll fluorescence also indicate the smallest damage to the photosynthetic apparatus in the plants on which these bacterial biostimulants were used. Under drought, the lowest initial fluorescence values were noted for these bacterial preparations, as were the highest values of maximum fluorescence. On the other hand, a parameter indicating stress was reduced due to drought in all plants, except for those treated with one of these preparations. Another parameter showing the efficiency of the use of light photons in the photosynthesis process increased only in plants treated with one of these preparations, whereas for other plants it decreased due to drought, with the smallest decrease observed in plants treated with the other preparations. The most effective work of the photosynthetic apparatus in such treated plants was observed by the fastest transport of electrons through photosystems under drought. Additionally, under drought, the highest grain yield was obtained in plants treated with one of these bacterial preparations. The drought stress resistance index indicated that among all tested formulations, plants treated with either of these bacterial preparations scored the best. The use of these two biostimulants is recommended for comparative efficacy studies in the field, to help combat the drought-related yield losses of wheat.