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Environmental stresses are forcing breeders to produce new plant genotypes with higher resistance to stressors. Biochemical markers of stress tolerance would assist in the selection of tolerant cultivars on the early stages of plant development. The aim of these studies was to examine whether the concentration of micro and macroelements of embryos and/or endosperm could specify the wheat grains in terms of their tolerance to stress conditions. Two sensitive to drought (Radunia and Raweta), two tolerant (Nawra and Parabola) and one with intermediate tolerance (Manu) were chosen. After dividing embryos and endosperm, the microelements content (Mn, Fe, Cu, Zn and Mo) was analyzed by inductively coupled plasma mass spectrometry (ICP-MS) and macroelements (K, Ca, Mg, P and S) by inductively coupled plasma optical emission spectrometry (ICP-OES). Independent of genotype, the concentration of all elements was higher in embryos than in endosperm. In both embryos and endosperm of tolerant plants, higher content of microelements (except for Cu in embryos) was detected. The accumulation of macroelements was lower in embryos of tolerant plants (except for K), however, in the case of endosperm, higher amounts of these elements, were registered. In embryos of Manu genotype, the content of microelements was more alike to sensitive and macroelements to tolerant plants but in endosperm, the level of both micro- and macroelements was more similar to tolerant ones. It was concluded that mineral composition of wheat grains, especially those in embryos, could inform about possible resistance of genotypes to stress conditions.

The comparative responses of ten spring wheat cultivars to water stress were investigated. Wheat plants were cultured under hydroponics conditions (Hoagland nutrient) to the stage of three-leaf seedlings. Then, the water medium was supplemented with PEG (drought) or NaCl (salinity) to obtain a water status equal to - 1.5 MPa. After a 2-day treatment, the changes in the following parameters were determined: fresh and dry weight, macro- and microelement accumulation, membrane injury (elec- trolyte leakage, lipid peroxidation) and fatty acid content of the phospholipid fraction of plasmalemma (in comparison to plants not stressed, taken as a control). Generally, the plants were more significantly influenced by water stress stimulated by PEG than by NaCl treatment, as compared to the plants cultivated in the control media. The results of the decrease in water content in leaves and electrolyte leakage from cells corresponded well with the intensity of lipid peroxidation (determined by malondialdehyde—MDA- content) and were chosen for the selection of investigated genotypes for tolerance to both stresses. The more tolerant genotypes exhibited the opposite changes in phospholipid fatty acid unsaturation for two applied stresses i.e. NaCl treatment caused a decrease in unsaturation whereas in PEG-treated plants an increase in unsaturation was observed. These changes were reversed for less tolerant plants, i.e. NaCl treatment influenced an increase in fatty acid unsaturation whereas in PEG-treated plants a decrease in unsaturation was measured. The ratio of U/S (unsatu- rated to saturated fatty acids) correlated with the total amount of accumulated macroelements. The content of Mg, Ca and S in leaves of plants undergoing both stress factors (NaCl and PEG) dropped whereas the K and P content increased in leaves of wheat seedlings cultured on media containing NaCl only. For microelements, a decrease in the accumulation of these nutrients was detected in all investigated seedlings. However, a greater reduction in the level of these elements occurred in seed- lings grown on media with PEG in comparison to those grown on NaCl containing media.

Manganese, a microelement important for plant metabolism, when accumulated at higher doses, may act as a stress factor. Such action of this element is not fully recognized and is currently being intensively studied. The influence of manganese, at high (1, 2 and 3 mM) concentrations, on the induction of oxidative stress in wheat cells was studied under in vitro conditions. Calli of two wheat cultivars, different in terms of stress tolerance, were cultured for 7 days on Murashige–Skoog media with or without auxin (2,4-D) and with additional Mn supplementation. Changes of malondialdehyde (MDA) concentration and the activity of enzymes (SOD, CAT and POX) involved in oxidative response as well as the accumulation of Mn and elements essential for plant development (Mn, Mg, S, Ca, K, P, Na, Zn, Mo, Cu, Fe) were detected. Moreover, proline and carbohydrate contents were determined to check the induction of osmotic stress. An increase of lipid peroxidation (expressed by MDA content), induced by ROS generation, was smaller in the tolerant (‘Parabola’) cultivar than in the sensitive one (‘Raweta’). The activation of antioxidative enzymes was more effective in the cells of tolerant wheat, where a lower quantity of Mn was accumulated. Mn uptake was correlated with a decrease of an amount of almost all the investigated elements. Auxin presence in the culture media accelerated the stressogenic effect of Mn.

Effects related to the adaptation of wheat to Mn excess were determined by structural and biochemical characterization of chloroplasts obtained from three-leaf seedlings of Mn-treated wheat. Chloroplasts were isolated from two wheat genotypes: sensitive (Raweta) and tolerant (Parabola) cultivated in hydroponic conditions in Hoagland nutrient supplemented with 0 (control), 5, 10, and 20 mmol dm−3 MnSO4. Microscopic observations of the chloroplast structure revealed differences in the size and starch presence between both objects. Changes indicating the stresogenic influence of Mn on Raweta seedlings appeared already at the Mn dose of 10 mmol dm−3, whereas on Parabola, only at 20 mmol dm−3. Biochemical analysis indicated the differences in starch content. Results of measurements of lipid peroxidation, polarity, and electrokinetic potential of chloroplasts point to Mn-stimulated modifications of chloroplast membranes which occurred to be larger for Raweta. The activation of antioxidative enzymes (SOD and POX) shows that ROS are generated under Mn-excess conditions. The content of Mn and Cu, Fe, Mo, and Zn (microelements) as well as Ca, Mg, K, P, and S (macroelements) in chloroplasts was determined by mass (ICP MS) and plasma optic emission (ICP OES) spectrometry. Raweta accumulated greater amount of Mn in comparison with Parabola at all Mn doses in media. Increased concentration of Mn was accompanied with a decrease of uptake other investigated elements (except for K).