Methyl jasmonate (MJ) is an important plant growth regulator that plays a key role in tolerance to biotic and abiotic stresses. In this research, the effects of exogenous MJ on cold tolerance, photosynthesis, activity and gene expression of antioxidant enzymes, proline accumulation, and expression of cold-regulated (COR) genes in wheat seedlings under low temperature (4 °C) were investigated. Exogenous MJ treatment (1 µM) promoted wheat cold tolerance before and during cold exposure. Low temperature significantly decreased photosynthetic parameters, whereas MJ application led to their partial recovery under cold exposure. Hydrogen peroxide (H₂O₂) and malondialdehyde (MDA) levels increased in response to low temperature, and this was counteracted by MJ application. Exogenous MJ significantly enhanced the activities of antioxidant enzymes and upregulated the expression of MnSOD and CAT during cold exposure. MJ application also led to enhanced proline content before 4 °C exposure, whereas the P5CS gene expression was upregulated by MJ’s presence at both normal (22 °C) and low (4 °C) temperatures. It was also shown that MJ tended to upregulate the expression of the COR genes WCS19 and WCS120 genes. We conclude that exogenous MJ can alleviate the negative effect of cold stress thus increasing wheat cold tolerance.

The effect of salicylic acid (SA) on the reaction of cucumber plants (Cucumis sativus L.) on the effect of low positive temperatures has been studied. It was found that treatment with SA promotes a decrease in the release of electrolytes from the tissues of cotyledonous leaves of seedlings exposed to subdamaging (12°C) and damaging (4°C) temperatures. In the leaves of seedlings treated with SA and exposed to cold, a higher activity of superoxide dismutase, catalase, and guaiacol-specific peroxidase was recorded as well as an increase in the accumulation of transcripts of the genes encoding them (CuZnSOD and CAT) compared to the control variant (without SA treatment). Under the action of low temperatures (12 and 4°C) on seedlings, SA also reduced the formation of one of the end products of lipid peroxidation, malondialdehyde, in seedling leaves. It was concluded that SA has a protective effect on cucumber seedlings when exposed to low positive temperatures, which is expressed in the activation of antioxidant enzymes and a decrease in the level of oxidative stress.

The effect of seed treatment with salicylic acid (SA) on the carbonic anhydrase (CA) activity, photosynthesis rate, stomatal conductance, and pigment content in wheat leaves was studied at an optimal zinc content (2 μM) and zinc excess (1500 μM). It was shown for the first time that the CA activity and stomatal conductance increased upon seed treatment with SA at the optimal zinc content as compared with untreated plants, while the photosynthesis rate was not affected. When zinc was in excess in the root zone, seed treatment with SA decreased the CA activity to a greater extent, but the photosynthesis rate was higher than in untreated plants, apparently due to an increase in the contents of chlorophylls and carotenoids and stomatal conductivity. It was concluded that SA is involved in the protective and adaptive responses of wheat plants to excess environmental zinc along with other nonhormonal factors and hormones.

The aim of this study was to investigate the effect of zinc (Zn) deficiency on the growth and grain yield of wheat with different allele statuses of the Gpc-B1 gene. For this research, common wild emmer wheat (Triticum turgidum ssp. dicoccoides (Koern. ex Asch. &Graebn.) Schweinf.), bread wheat (Triticum aestivum L. cv. Festivalnaya), and two intogressive lines were used. T. dicoccoides and introgressive line 15-7-1 carry a functional allele of the Gpc-B1 gene, while the T. aestivum cv. Festivalnaya and introgressive line 15-7-2 carry the non-functional Gpc-B1 allele. Zn deficiency did not affect the shoot height or fresh weight of any of the studied plants. The only exception was T. dicoccoides, where a small decrease in shoot height was registered. Additionally, under Zn deficiency T. dicoccoides had an increase in flag leaf area, spike length, and dry weight, as well as in grain number and grain yield per spike. The other variants did not experience changes in the above-described parameters under Zn deficiency. Under Zn deficiency, the Zn concentration in the grains was higher in the plants with a functional allele of the Gpc-B1 gene compared to the plants with a non-functional allele. These results show that wheat with a functional allele of the Gpc-B1 gene growing under Zn deficiency is capable of grain production with a sufficient Zn concentration without a decrease in yield.

We studied the effect of seed treatment with salicylic acid (SA, 100 μM) on seed germination, growth, the level of lipid peroxidation (LPO), and the functioning of a number of components of the antioxidant system in wheat plants (Triticum aestivum L.) Zlata variety grown with optimal (2 μM) or excess (1500 µM) zinc content in the root environment. It has been shown that excess zinc has an inhibitory effect on root and shoot growth and also enhances the accumulation of one of the indicators of LPO development: malondialdehyde (MDA). At the same time, the structural integrity of the membranes was maintained, as indicated by the absence of changes in membrane permeability, recorded by the yield of electrolytes. The activity of antioxidant enzymes, superoxide dismutase (SOD) and catalase (CAT), did not change under these conditions, but the activity of guaiacol-specific peroxidase (GPO) decreased. Treatment of seeds with SA at a concentration of 100 μM, which stimulates their germination, enhanced the negative effect of excess zinc on growth performance and MDA accumulation in wheat leaves. However, in this case, the yield of electrolytes did not increase, which is presumably due to an increase in the activity of SOD and GPO. Based on the data presented in the work and previously obtained, as well as an analysis of the literature, it was concluded that the response of plants to excess zinc in the external environment, like the reaction to other abiotic stresses, is not only multicomponent and multiechelon but also variable, depending on many factors and circumstances: the dose of exposure (zinc concentration and duration of its action), biological characteristics of the plant species (variety), their age condition, etc. Treatment of seeds with SA can change the nature of the plant’s response to the action of excess zinc, and the direction of these changes will, in turn, depend on the concentration of SA, the duration of its action, and the method of treatment.