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Two kinds of barley genotypes with various water-stress tolerances, tolerant Cam/B1 and sensitive Maresi, were subjected to 10-day soil-drought stress in seedling and flag leaf developmental phases. After this time, both genotypes regardless of the growth stage showed a decrease in quantum yield of PSII photochemistry (Φ PSII ) upon stress treatment; however, this effect was stronger in the sensitive plants than in the tolerant ones. The drought stress in the flag leaf stage was associated with an increase in superoxide dismutase (SOD) level in both genotypes, whereas in seedlings, this effect was observed only for Maresi. The activity of other enzymes (catalase and peroxidase) was changed only in small degree. An increase in proline levels and activities of D 1 -pyrroline-5-carboxylate synthetase (P5CS) and ornithine delta-aminotransferase (OAT) were observed independently of genotype and the phase of plant development, whereas the activity pyruvate dehydrogenase (PDH) decreased in tolerant genotype. Moreover, changes in the concentration of monocarbohydrates (glucose and fructose) and dicarbohydrates (saccharose, raffinose and maltose) were found: in seedlings, the amount of all soluble sugars increased, while in flag leaves decreased. The drought treatment resulted in a drop in starch level in the tolerant genotype, but in the sensitive one, the content of this substance increased in both developmental stages. EPR studies allowed the determination of the amount and character of organic radicals present in leaves. In control conditions, the content of these radical species was higher in the sensitive genotype than in tolerant one and decreased upon water stress, with the exception of flag leaves of the sensitive plant. Simulation procedure revealed four types of signals in the EPR spectra. One of them was attributed to a chlorophyll a cation and decreased upon drought. The second, ascribed to semiquinone radicals, reflected the redox balance disturbed by water deficit. The two remaining signals were connected with carbon-centred radicals situated in the carbohydrate matrix. Their number was correlated with starch concentration.

The aim of this work was to evaluate the effect of potassium and magnesium treatment on physicochemical and rheological properties of native potato, corn, and spelt starches. Treatment of starch by one of the metals resulted in an increase in the amount of the used element, with the increase accompanied by decrease in the amount of the other metal. Starches fortified with metal ions did not differ significantly from the native starches in gelatinization characteristics. Effect of metal ions on rheological behavior of starch pastes was the greatest in corn starch with potassium. In the case of the other pastes the effect depended both on type of starch and kind of metal ions. The modified starches formed harder gels than the native starches. Starches treated with potassium ions showed lower rate of retrogradation than the respective native starches. The modified starches were also more susceptible to enzymatic hydrolysis than their native counterparts. Thermal treatment of native and modified with potassium and magnesium starches led to formation of carbohydrate radicals, which character and amounts depended on the starch origin as well as the kind of metal ions. Spelt starch was the most susceptible to the formation of radicals, whereas the structure of corn starch was the most stable. Effects of metal ions were opposite: potassium ions increased, whereas magnesium ones decreased the amount of radicals in comparison with native spelt starch.

These studies concentrate on the possibility of using selenium ions and/or 24-epibrassinolide at non-toxic levels as protectors of wheat plants against zearalenone, which is a common and widespread mycotoxin. Analysis using the UHPLC-MS technique allowed for identification of grains having the stress-tolerant and stress-sensitive wheat genotype. When germinating in the presence of 30 µM of zearalenone, this mycotoxin can accumulate in both grains and hypocotyls germinating from these grains. Selenium ions (10 µM) and 24-epibrassinolide (0.1 µM) introduced together with zearalenone decreased the uptake of zearalenone from about 295 to 200 ng/g and from about 350 to 300 ng/g in the grains of tolerant and sensitive genotypes, respectively. As a consequence, this also resulted in a reduction in the uptake of zearalenone from about 100 to 80 ng/g and from about 155 to 128 ng/g in the hypocotyls from the germinated grains of tolerant and sensitive wheat, respectively. In the mechanism of protection against the zearalenone-induced oxidative stress, the antioxidative enzymes—mainly superoxide dismutase (SOD) and catalase (CAT)—were engaged, especially in the sensitive genotype. Electron paramagnetic resonance (EPR) studies allowed for a description of the chemical character of the long-lived organic radicals formed in biomolecular structures which are able to stabilize electrons released from reactive oxygen species as well as the changes in the status of transition paramagnetic metal ions. The presence of zearalenone drastically decreased the amount of paramagnetic metal ions—mainly Mn(II) and Fe(III)—bonded in the organic matrix. This effect was particularly found in the sensitive genotype, in which these species were found at a smaller level. The protective effect of selenium ions and 24-epibrassinolide originated from their ability to inhibit the destruction of biomolecules by reactive oxygen species. An increased ability to defend biomolecules against zearalenone action was observed for 24-epibrassinolide.

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