The effect of methyl jasmonate (MeJA) treatment on diploid and tetraploid plants of Matricaria chamomilla and the changes of the main physiological parameters and secondary metabolites content was studied. Leaf rosettes from 7-week-old plants were harvested at four different time points (24, 48, 72, 96 h) after foliar application of 0.4 mM MeJA. The treatment led to a moderate biomass accumulation accompanied by an accumulation of photosynthetic pigments and decrease in the total soluble proteins. The content of hydrogen peroxide and superoxide radical was most elevated at 24 and 72 h after the treatment. Although the values of stress parameters were higher in tetraploid plants (such as in control so in treated plants), their total increase after the MeJA application was similar. The absolute level of total soluble phenols and flavonoids in the controls was similar in both cultivars and their content was enhanced in 24-and 48-h variants, more rapidly in diploid plants. MeJA has been found to trigger different responses of the secondary metabolites accumulation. Almost all studied metabolites were higher in control plants in the tetraploid cultivar, but their biosynthesis was more stimulated in diploids. Significant changes, mainly increasing trends with a maximum between 24 and 48 h after elicitation, in the content of free coumarin herniarin and its glycosidic precursors (Z)-and (E)-2-b-D-glucopyranosyloxy-4-methoxycinnamic acid were observed. The umbelliferone level increased over time. The maximum values for chlorogenic acid and 1,5-dicaffeoylquinic acid were at 24-h and between the 24-72 h time points. Among dicycloethers, the amounts of (E)-form decreased with time, and for (Z)-form an opposite trend was observed, with a maximum of 96 h for diploid and 24 h for tetraploid after elicitation.

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Enhanced UV-B irradiation is one of the most important abiotic stresses that can influence various aspects of plant morphology, biochemistry and physiology. Silicon as a beneficial element can increase the plant's tolerance against different abiotic stresses, including UV-B stress. In this work, the effect of silicon supplementation on the sensitivity of young maize (Zea mays L.) seedlings exposed to short-term UV-B radiation was studied. The seedlings were grown with 0 or 5 mM silicon in cultivation medium and on the fifth day of cultivation, they were exposed for 15 and 30 min to UV-B (302 nm) radiation. No significant changes in growth and content of assimilation pigments and the chlorophyll a/b ratio were observed in any of tested irradiation periods in control or Si-treated plants. Under UV-B stress, the content of ROS (hydrogen peroxide and superoxide radical) and TBARS increased in control plants. The oxidative status of Si-treated plants was only slightly affected even after 30 min. Phenolic metabolites (total phenols and flavonoids), important for their screening function under radiation stress, slightly increased after UV-B exposure in control plants, however, only flavonoids increased after 30 min in Si-treated plants. The measured parameters indicated that to some extent silicon supplementation contributes to higher UV-B tolerance of maize seedlings.