Various abiotic stresses cause the appearance of reactive oxygen species (ROS) in plant cells, which seriously damage the cellular structures. The engineering of transgenic plants with higher production of ROS-scavenging enzyme in plant cells could protect the integrity of such a fine intracellular structure as the cytoskeleton and each cellular compartment. We analyzed the morphological changes in root tip cells caused by the application of iso-osmotic NaCl and Na₂SO₄ solutions to tomato plants harboring an introduced superoxide dismutase gene. To study the roots of tomato plants cultivar Belyi Naliv (WT) and FeSOD-transgenic line, we examined the distribution of ROS and enzyme-linked immunosorbent detection of α-tubulin. In addition, longitudinal sections of the root apexes were compared. Transmission electronic microscopy of atypical cytoskeleton structures was also performed. The differences in the microtubules cortical network between WT and transgenic plants without salt stress were detected. The differences were found in the cortical network of microtubules between WT and transgenic plants in the absence of salt stress. While an ordered microtubule network was revealed in the root cells of WT tomato, no such degree of ordering was detected in transgenic line cells. The signs of microtubule disorganization in root cells of WT plants were manifested under the NaCl treatment. On the contrary, the cytoskeleton structural organization in the transgenic line cells was more ordered. Similar changes, including the cortical microtubules disorganization, possibly associated with the formation of atypical tubulin polymers as a response to salt stress caused by Na₂SO₄ treatment, were also observed. Changes in cell size, due to both vacuolization and impaired cell expansion in columella zone and cap initials, were responsible for the root tip tissue modification.

The high salinity of soil salts limits plant growth. Wheat is sensitive to toxic levels of mineral salts. Salinity leads to the accumulation of toxic ions in all organs of wheat. Depending on the level of ion accumulation, wheat is defined as salt stress-tolerant or -sensitive. The wheat variety Zolotaya accumulated Cl⁻ and Na⁺ ions to a greater extent than the Orenburgskaya 22 variety. The accumulation of toxic ions was accompanied by an increase in ROS and an increase in damage to root tissues up to 80% in the Zolotaya variety. The formation of autophagosomes is considered a defense mechanism against abiotic stresses in plants. At a concentration of 150 mM NaCl, an increase in the expression level of TOR, which is a negative regulator of the formation of autophagosomes, occurred. The level of TOR expression in the Zolotaya variety was 2.8 times higher in the roots and 3.8 times higher in the leaves than in the Orenburgskaya 22 variety. Under the action of salinity, homeostasis was disturbed in the root cells and ROS production accumulated. In the unstable variety Zolotaya, ROS was found in the cap zone and the root meristem in contrast to the resistant variety Orenburgskaya 22 in which ROS production was found only in the cap zone. Accumulation of ROS production triggered autophagy and PCD. PCD markers revealed DNA breaks in the nuclei and metaphase chromosomes, cells with a surface location of phosphatidylserine, and the release of cytochrome c into the cytoplasm, which indicates a mitochondrial pathway for the death of part of the root cells during salinity. Based on electron microscopy data, mitophagy induction was revealed in wheat root and leaf cells under saline conditions.

Various stressors lead to an increase in ROS and damage to plant tissues. Plants have a powerful antioxidant system (AOS), which allows them to neutralize excess ROS. We detected an intense fluorescent glow of ROS in the cells of the cap, meristem, and elongation zones in the roots of wheat Triticum aestivum (Orenburgskaya 22 variety) and Triticum durum (Zolotaya variety). An increase in ROS was accompanied by DNA breaks in the nuclei of wheat root cells, the release of cytochrome c from mitochondria into the cytoplasm, and the translocation of phosphatidylserine into the outer layer of the plasma membrane under salt stress and hypoxia. The different resistances of the two wheat varieties to different abiotic stresses were revealed. The soft wheat variety Orenburgskaya 22 showed high resistance to salt stress but sensitivity to hypoxia, and the durum wheat variety Zolotaya showed tolerance to hypoxia but high sensitivity to salt stress. Different activations of AOS components (GSH, MnSOD, Cu/ZnSOD, CAT, PX, GPX, and GST) were revealed in different wheat genotypes. The basis for the tolerance of the Zolotaya variety to hypoxia is the high content of glutathione (GSH) and the activation of glutathione-dependent enzymes. One of the mechanisms of high resistance to salt stress in the Orenburgskaya 22 variety is a decrease in the level of ROS as a result of the increased activity of the MnSOD and Cu/ZnSOD genes. Identifying the mechanisms of plant tolerance to abiotic stress is the most important task for improving breeding varieties of agricultural plants and increasing their yield.

The toxicity of high concentrations of sodium chloride creates significant difficulties in realizing the productivity potential of wheat. The development of effective test systems for the identification and selection of resistant genotypes is an urgent task given the global increase in soil salinity in agricultural land. To identify the characteristics of the plant’s reaction to the toxic effect of sodium chloride, wheat genotypes with different resistance to ionic toxicity (the Orenburgskaya 10 and Orenburgskaya 22 varieties) were used. In model experiments, we used fluorescence, light-optical and electron microscopy to characterize the structural and functional features of the cells of the roots of wheat seedlings, and cytological markers suitable for creating a test system for the early diagnosis of the sensitivity of wheat genotypes to sodium chloride were established. The response of the plants to the effects of sodium chloride was assessed by changes in biometric data, respiration rate, peculiarities in the accumulation of reactive oxygen species (ROS) and mitochondrial staining, and the quantitative assessment of coleoptile cell viability as putative sensitivity markers. In the sodium chloride-sensitive genotype (Orenburgskaya 10), toxic effects resulted in oxidative damage in the root cells, while in the resistant genotype (Orenburgskaya 22), oxidative damage to the cells was minimal. A high level of expression of mitochondrial superoxide dismutase (MnSOD) was found in the roots of the Orenburgskaya 22 variety. The identification and functional analysis of cytological and molecular markers provide the basis for further studies of the resistance of wheat to sodium chloride stress.

Like phytohormones, peptide hormones participate in many cellular processes, participate in intercellular communications, and are involved in signal transmission. The system of intercellular communications based on peptide–receptor interactions plays a critical role in the development and functioning of plants. One of the most important molecules are reactive oxygen species (ROS). ROS participate in signaling processes and intercellular communications, including the development of the root system. ROS are recognized as active regulators of cell division and differentiation, which depend on the oxidation–reduction balance. The stem cell niche and the size of the root meristem are maintained by the intercellular interactions and signaling networks of peptide hormone and ROS. Therefore, peptides and ROS can interact with each other both directly and indirectly and function as regulators of cellular processes. Peptides and ROS regulate cell division and stem cell differentiation through a negative feedback mechanism. In this review, we focused on the molecular mechanisms regulating the development of the main root, lateral roots, and nodules, in which peptides and ROS participate.

Determining salt tolerance potential in wheat is one of the most important problems in breeding practice for areas with primary and secondary salinity. Presence of large areas of saline soils results in inhibition of growth, development and stability in obtaining high yields of agricultural plants. Therefore, there is a need for a comprehensive studying and improving of diagnostic methods during early growth stages. Different genotypes of wheat Triticum aestivum Host. and Triticum durum Desf. were used to identify salt tolerance markers. Both morphometric and some biochemical indicators of wheat varieties were used as salt tolerance markers. At this stage, it was shown that a comprehensive description of wheat varieties is needed to assess resistance of wheat varieties to chloride salinity.