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Gamma-aminobutyric acid (GABA) is considered an important stress metabolite with regulatory functions in plants. Exogenous GABA can enhance the tolerance of different plant species to drought and salt stress. However, its effects on the functioning of stress-protective systems in triticale, an intergeneric wheat-rye hybrid with specific adaptation strategies to abiotic stresses, remain completely understudied. We examined the effects of exogenous GABA (0.5 mM) on the growth, antioxidant, and osmoprotective systems of triticale seedlings (cv. 'Rarytet') under simulated drought (15% PEG 6000), salt stress (100 mM NaCl), or a combination of these two factors. GABA mitigated the growth-inhibitory effects of drought by approximately 15% and salt stress by approximately 23%. However, GABA's most noticeable impact was seen on biomass accumulation under combined stress: it decreased the biomass accumulation inhibition caused by a drought-salt stress combination by 67%; GABA also increased the water content in seedling tissues when subjected to each stressor separately and to the combination of the two. GABA considerably reduced drought- and salt-triggered enhancement of ROS generation and lipid peroxidation. GABA increased the activities of antioxidant enzymes, such as superoxide dismutase, catalase, and guaiacol peroxidase, under physiologically normal conditions under the influence of PEG 6000 or NaCl. Subjected to a drought-salt stress combination, GABA prevented a reduction in the activities of these enzymes. Under normal and stressful conditions, exogenous GABA also modulated the contents of proline, sugars, phenolic compounds, and anthocyanins in the seedlings. We concluded that the stress-protective systems of triticale were highly susceptible to GABA and that it was possible to use GABA to enhance the tolerance of this species to osmotic stresses, especially under a combined impact of drought and salinity. [ABSTRACT FROM AUTHOR]

The challenge of increasing plant tolerance to low temperatures is still relevant despite the upward trend in the average temperatures on Earth. Sharp temperature fluctuations during growing periods and cultivation of thermophilic crops in more northern latitudes increase the likelihood of plants being damaged by cold. Physiologically active substances, primarily hormones and signalling molecules, are considered to be effective for increasing plant tolerance to extreme temperatures. In the last decade, among such compounds, researchers' and practitioners' considerable attention has been paid to gasotransmitters - gaseous substances that are synthesized by living organisms and perform signalling functions. The review analyses the molecular mechanisms of stress protective effects of two major gasotransmitters - nitric oxide (NO) and hydrogen sulfide (H2S). In particular, the physiological effects of gasotransmitters that are attributed to their ability to cause post-translational modifications of numerous target proteins as well as those related to their functional interactions with other signaling intermediaries, primarily ROS and calcium ions, are discussed. The available data on the actions of donors of these gasotransmitters on thermophilic and cold-tolerant plants are summarized. Particular attention is paid to the influence of exogenous NO and H2S on the antioxidant system in plants, their ability to accumulate osmolytes and other low-molecular compounds with multifunctional stress protective effects. Data on the influence of gasotransmitters on fruits during low-temperature storage are analysed separately. It is emphasized that increased storability of fruits under the influence of NO and H2S donors is largely controlled by the ability of both gasotransmitters to inhibit ethylene synthesis. It was concluded that exogenous nitric oxide and hydrogen sulfide could be effective tools for increasing tolerance of different plant taxon's to low temperatures and used in crop production and storage technologies for fruits and vegetables. [ABSTRACT FROM AUTHOR]

This review considers the action of nitric oxide (NO) as a signaling molecule of plant cells, the effects of which can be modulated in crop production practice through the use of nitric oxide donors. The current understanding of nitric oxide synthesis in plants is briefly described. The characterization of synthesized and natural compounds that can be nitric oxide donors is given. The main molecular mechanisms of nitric oxide action in plant cells are characterized: post-translational modification of proteins under the action of NO, its influence on the content of other cellular mediators, in particular, reactive oxygen species and calcium ions. Considerable attention is paid to the functional interaction of nitric oxide with individual phytohormones and new groups of physiologically active substances of plants. Modern ideas on the mechanisms of nitric oxide action on seed germination and plant resistance to adverse abiotic factors are presented. Data on the effects of priming seeds with nitric oxide donors on their germination under optimal and stress conditions are discussed. [ABSTRACT FROM AUTHOR]

Extremely high temperatures affecting cotton plants at various stages of ontogenesis. Oxidative damage of cell structures inflicted by moderately high temperatures is a main cause for the deleterious effect of heat stress. However, the status of the protective antioxidant system (AOS) in cotton plants has been studied mainly at the generative stages of development, while peculiarities of its functioning in the juvenile plants of various genotypes remains underexplored. The work was done to study the reaction of growth and the AOS response to the heat stress in the 7-8-day seedlings of various cotton cultivars obtained by various selection methods differing in economically valuable features. Surkhan-103 and Bukhara-102, the cultivars generated by classical selection, as well as those generated by biotechnological methods with higher fiber quality, to cultivars Porlok-1, Porlok-2, Ravnak-1 and Ravnak-2, were the objects of experiments. The 7-day seedlings were exposed to the 6-hour effect of high temperature (45°C) to subsequently assess the increment of control and stressinflicted plants and to determine parameters of the AOS state and development of oxidative damages. Surkhan-103, Porlok-4 and Ravnak-2 cultivars were found to distinguish by significantly lower post-stress inhibition of growth of both seedlings and roots than those of Bukhara-102, Ravnak-1 and Porlok-1. The sensitive cultivars affected by heat stress demonstrated higher post-stress contents of hydrogen peroxide and malondialdehyde (MDA), a product of lipid peroxidation, in the leaves. At the same time, the resistant cultivars demonstrated higher activity of catalase and superoxide dismutase. The higher post-stress content of proline were typical of the resistant cultivars. A close direct correlation between inhibition of growth of seedlings and higher contents of hydrogen peroxide and MDA was demonstrated. In addition, high-level inverse correlation was demonstrated between the growth inhibition and higher catalase activity and proline content. The juvenile cotton plants were concluded to be promising in assessment of heat resistance and its dependence on the AOS state. [ABSTRACT FROM AUTHOR]

Melatonin is a multifunctional molecule whose biological activity has been intensively studied in recent years in the context of plant adaptation to abiotic stresses, including drought. However, comprehensive studies on the effect of melatonin on the status of antioxidant and osmoprotective systems in wheat varieties with different drought adaptation strategies have been lacking. We studied the effect of melatonin on the growth and functioning of stress protection systems of wheat (Triticum aestivum L.) seedlings of Tobak (drought-tolerant) and Doskonala (drought-sensitive) varieties. Two-day-old etiolated seedlings were transferred to a 15% PEG 6000 solution for 2 days to create a model drought. The addition of melatonin to the incubation medium of seedlings at concentrations in the range of 0.2-5.0 µM significantly alleviated the inhibition of root and shoot growth of seedlings caused by drought. The effects of melatonin were more pronounced in the drought-sensitive cultivar Doskonala. Melatonin treatment almost completely eliminated the effect of increased hydrogen peroxide content under drought conditions in both varieties. Also in Doskonala variety, melatonin treatment reduced stress-induced accumulation of lipid peroxidation products. Drought caused a decrease in superoxide dismutase activity in both varieties, while melatonin treatment helped to maintain the enzyme activity at a level close to that of the control variants. In both varieties, melatonin treatment also reversed the stress-induced decrease in guaiacol peroxidase activity. Under the influence of melatonin, proline accumulation was significantly enhanced in Doskonala under drought conditions. Drought caused a decrease in sugars and flavonoid compounds, while melatonin mitigated these effects in both varieties. It is concluded that melatonin significantly modulates the adaptive responses of etiolated wheat seedlings to drought and that its effects depend on cultivar characteristics. [ABSTRACT FROM AUTHOR]

The phenomenon of plant cross-tolerance to various stressors, particularly heat and drought, has been studied in considerable detail. However, there are no data on the relationship between resistance to these stressors in Triticum aestivum cultivars of different ecological and geographical origins at the stage of etiolated seedlings. At the same time, they are used for an accelerated assessment of the heat and drought resistance of breeding samples (separately for each factor). This work compared the response of seedlings of seven winter common wheat cultivars to heat stress (4-hour heating at 45°C) and a model drought (action of 12% PEG 6000). A correlation was found between the inhibition of seedling biomass accumulation as a whole (r=0.55) and separately for shoots (r=0.66) under heat and osmotic stress. A high correlation was shown between inhibition of shoot growth and accumulation of hydrogen peroxide and lipid peroxidation (LPO) products in shoots during heating (r=0.91 and 0.76, respectively) and a much lower correlation between the values of these markers of oxidative stress and inhibition of shoot growth during drought. A significant inverse correlation was found between the accumulation of sugars in the shoots and inhibition of shoot growth under drought (r=-0.85), and moderately high under heat stress (r=-0.60). At the same time, only a positive medium correlation (r=0.49) was observed between proline content and growth inhibition under both types of stress. However, a high positive correlation was found between proline and LPO products under drought conditions (r=0.91). It is concluded that the resistance of wheat seedlings to oxidative stress is more closely related to heat tolerance than to drought tolerance. The results also indicate a significant contribution of sugars, but not proline, to the resistance of wheat seedlings to drought and heat stress. [ABSTRACT FROM AUTHOR]

The response of etiolated seedlings of winter rye (Secale cereale), bread (Triticum aestivum) and durum (T. durum) wheats, as well as triticale (x Triticosecale) to the action of hyperthermia in relation to their resistance to oxidative stress was studied. Exposure of seedlings to 45°C for 4 hours led to a significant inhibition of the growth of T. aestivum, while the growth of T. durum and x Triticosecale seedlings was less sensitive to hyperthermia, and S. cereale seedlings showed the greatest resistance to heat stress. In bread wheat seedlings after heating, intensive development of oxidative stress. In durum wheat and triticale, such effects were less pronounced, and in rye, they were almost absent. In rye, triticale, and durum wheat seedlings, peroxidase activity increased under hyperthermia conditions, while in bread wheat, on the contrary, it decreased. In all four studied cereals, in response to the action of high temperature, the content of multifunctional stress metabolite proline increased, however, in rye, its absolute content significantly exceeded that in other species. The content of sugars during hyperthermia increased in S. cereale and T. durum, but did not change in the other two cereals. Triticale and especially rye have a high base content of anthocyanins and its increase in response to high temperature. A conclusion was made about the relationship between the ability of cereal seedlings to maintain growth under the action of hyperthermia and their resistance to oxidative stress, which is mainly due to the accumulation of metabolites with antioxidant activity. [ABSTRACT FROM AUTHOR]