Although growth stimulation at low arsenic doses was observed in several plants, few studies have focused on this phenomenon in more detail. The effects of different concentrations of arsenic (0–50 mg kg⁻¹ of soil: As0–As50) on the growth and selected physiological parameters of two maize cultivars (Zea mays L. cvs. Chapalu and MvNK 333) were tested. Cultivar MvNK 333 manifested a generally higher tolerance to As than cv. Chapalu, which may be related to the lower content of As in the tissues. The highest stimulatory effect of As was recorded at doses of As1 and As2 (cv. Chapalu), and at the As5 dose (MvNK 333), there was an increase in shoot elongation, biomass, and relative water content (RWC), as well as the content of photosynthetic pigments. The stimulatory effect of lower doses of As apparently represents an adaptation mechanism that is associated with water content regulation in the given conditions. The stomata of the studied cultivars were involved in this regulation in different ways. While cv. Chapalu exhibited increased numbers of stomata on both sides of leaves, cv. MvNK 333 instead responded to the given conditions with decreased stomata size. Although hormetic manifestations closely related to changes in stomatal number and size were observed, a typical stomatal hormetic response was not observed in the given range of As doses.

In addition to the structural and storage functions of the (1,3; 1,4)-β-d-glucans (β-d-glucan), the possible protective role of this polymer under biotic stresses is still debated. The aim of this study was to contribute to this hypothesis by analyzing the β-d-glucans content, expression of related cellulose synthase-like (Csl) Cs1F6, CslF9, CslF3 genes, content of chlorophylls, and β-1,3-glucanase content in oat (Avena sativa L.) leaves infected with the commonly occurring oat fungal pathogen, Blumeria graminis f. sp. avenae (B. graminis). Its presence influenced all measured parameters. The content of β-d-glucans in infected leaves decreased in all used varieties, compared to the non-infected plants, but not significantly. Oats reacted differently, with Aragon and Vaclav responding with overexpression, and Bay Yan 2, Ivory, and Racoon responding with the underexpression of these genes. Pathogens changed the relative ratios regarding the expression of CslF6, CslF9, and CslF3 genes from neutral to negative correlations. However, changes in the expression of these genes did not statistically significantly affect the content of β-d-glucans. A very slight indication of positive correlation, but statistically insignificant, was observed between the contents of β-d-glucans and chlorophylls. Some isoforms of β-1,3-glucanases accumulated to a several-times higher level in the infected leaves of all varieties. New isoforms of β-1,3-glucanases were also detected in infected leaves after fungal infection.

In this study, we evaluate the mechanisms of oat tolerance under various stress conditions. Five oat varieties were exposed to cadmium ions (Cd²⁺, 50 mg kg ^− 1 soil) after 22 days of cultivation in soil substrate, and to Blumeria graminis after 33 days. Simultaneously, the response of oats to both stressors was assessed (variant P + Cd) in the context of changes in the activity of β-1,3-glucanases and chitinases. Overall, we detected six isoforms of total β-1,3-glucanases (35–140 kDa) and six total chitinases (23–260 kDa) on polyacrylamide gels. The increased activity of most isoforms (total, acidic, and basic) of these enzymes in infected leaves confirms their major role in defence against the pathogen, and we also recorded de novo accumulation of some isoforms. Changes in their activity were dependent on genotype, experimental variant, and isoform. Some isoforms of β-1,3-glucanases and chitinases were also Cd-responsive. The reduced activity of certain β-1,3-glucanase isoforms (48 kDa) suggests their involvement in other defence mechanisms, likely related to the synthesis or degradation of other polysaccharides. The metal’s protective effect was not clearly confirmed in the context of the response to powdery mildew. Metal content in tissues did not correlate with the activity of β-1,3-glucanases and chitinases in any metal variant of the experiment.