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The effect of melatonin on growth parameters, the photochemical activity of photosystem II (PS II), the content of the main photosynthetic pigments, and lipid peroxidation in barley plant leaves under polymetallic stress were studied. Melatonin reduces the toxic effect of polymetals on biomass accumulation, root growth, and maintenance of the assimilating surface. The protective action of the hormone is based on its ability to reduce the intensity of oxidative stress by maintaining the level of carotenoids and increasing the activity of superoxide dismutase, but not by regulating the photochemical activity of chloroplasts. The effectiveness of melatonin does not depend on the duration of exposure. The data obtained can be the basis for optimizing the use of melatonin as a plant priming inducer.

A comparison was made of the physiological activity of brassinosteroids (BS) of different chemical structures—lactone-containing 24-epibrassinolide (EBL) and ketone-containing brassinosteroid 24-epicastasterone (ECS)—during dark aging of cut barley (Hordeum vulgare L.) leaves. The functional state of the photosynthetic apparatus, the amount of photosynthetic pigments, the content of lipid peroxidation products, and gene expression of HvS40 (senescence marker) were assessed. The separated barley leaves were incubated on solutions of EBL and ECS in the concentration range of 0.01–1 µM in Petri dishes on filter paper. Synthetic cytokinin 6-benzylaminopurine (BAP) at a 10 μM concentration was used as a positive control, and distilled water was used as a negative control. Petri dishes with leaves were kept in the dark for 5 days. Measurements of the analyzed parameters were carried out on the first, third, and fifth days from the beginning of incubation, mainly in the middle part of the leaf plate. ECS at a concentration of 1 μM reduced oxidative stress by the fifth day of incubation to a greater extent than EBL at a similar concentration. Regarding maintenance of chlorophyll a (Chl a) levels, 24-epicastasterone (1 μM) was more effective than 24-epibrassinolide. It was shown that exogenous brassinosteroids showed a protective effect on the main photochemical processes of the second photosystem during aging of barley leaves. Moreover, when assessing the coefficient of nonphotochemical quenching (qN), indicators of regulated (Y(NPQ)) and nonregulated (Y(NO)) energy dissipation, the ECS showed a more pronounced protective effect for the second photosystem compared to EBL. It was found that treatment with brassinosteroids reduced the level of gene expression of HvS40, a senescence marker on the fifth day of incubation, which was especially characteristic for the ketone-containing brassinosteroid. Thus, it can be concluded that the ketone-containing brassinosteroid not only exhibits high biological activity but, in terms of a number of parameters, is also more effective than the lactone-containing brassinosteroid in reducing the damage caused by aging.

The ability of brassinosteroids (BS) of different chemical structures (for example, 24-epibrassinolide (EBL) and 24-epicastasterone (ECS)) to induce priming in rapeseed (Brassica napus L.) plants, increasing resistance to “delayed” salt stress (150 mM NaCl), was studied. After 2 weeks of growth of rapeseed seedlings in a hydroponic setup in Hoagland-Snyder (HS) medium, they were transferred to the same medium supplemented with EBL or ECS (10 nM) for 4 h. The plants were then kept on the HS medium without BS for 20 h. Then they were grown on HS nutrient medium in the absence or in the presence of 150 mM NaCl for 6 days. Salinization inhibited growth processes (stem length, number of leaves, assimilating surface area, raw mass of plants (by 30–35%)); decreased levels of chlorophylls a and b and carotenoids (by 38–44%), tissue water content (by 3.54%), and osmotic potential of cells (1.7 times); and increased lipid peroxidation (LPO) (by 62%) in leaves. At the same time, salt stress stimulated the level of proline in leaves by six times and in stems and roots by 11 times, the activity of superoxide dismutase (SOD) by 2.3 times, and the activity of peroxidase by 26%. The concentration (at %) of Na and Cl under salinization increased in all parts of the plants, but the concentration of K, Ca, Mg, S, P, Al, and Fe ions decreased. Treatment of plants with BS (10 nM, 4 h) stimulated growth processes under optimal conditions, which was more typical for ECS, which also increased the content of chlorophyll a and carotenoids (by 11 and 18% in leaves, respectively). BS stimulated the activity of antioxidant enzymes (EBL increased the activity of SOD by 4.6 times, ECS increased the activity of SOD and peroxidase (by 48%)), which could affect the development of the priming state in plants. Pretreatment of rape seedlings with BS increased their resistance to subsequent salt stress. The protective effect of BS manifested at the levels of growth responses (primarily in ECS), water status, and osmotic potential of leaves. The LPO level decreased due to the activation of SOD and peroxidase in the case of EBL and ECS, respectively. The accumulation of ions in plants subjected to hormonal priming depended on the chemical structure of BS. It has been suggested that the protective effect of BS priming is explained by the ability of hormones to activate antioxidant enzymes before stress and to influence the inorganic ion transport system in such a way that plants accumulate ions more actively with subsequent salinization, resulting in a decrease in the osmotic potential of cells and maintenance of the water status. The obtained results can be useful in the development of technology for increasing the salt tolerance of rapeseed.

Melatonin supports the photochemical activity of photosystem II (PS II) and slows down the degradation of the main photosynthetic pigments during aging of leaves of monocotyledonous plants. The protective effect of melatonin is manifested in an increase in the maximum (Fv/Fm) and effective (Y(II)) quantum yield of PS II, in an increase of regulated (Y(NPQ)) and a decrease in unregulated dissipation of excitation energy (Y(NO)). These effects are based on the ability of melatonin to reduce the intensity of oxidative stress by maintaining a high level of carotenoids, which exhibit pronounced antioxidant properties, during aging.

The effect of polymetallic stress (Mn

Brassinosteroids are promising agents for alleviating the negative effects of salinity on plants, but the mechanism of their protective action is far from being understood. We investigated the effect of pretreatment with 24-epibrassinolide (24-EBL) on the photosynthetic and physiological parameters of potato plants under progressive salinity stress caused by root application of 100 mM NaCl. Salinity clearly inhibited primary photosynthetic processes in potato plants by reducing the contents of photosynthetic pigments, photosynthetic electron transport and photosystem II (PSII) maximal and effective quantum yields. These negative effects of salinity on primary photosynthetic processes were mainly due to toxic ionic effects on the plant’s ability to oxidize the plastoquinone pool. Pretreatment with 24-EBL alleviated this stress effect and allowed the maintenance of plastoquinone pool oxidation and the efficiency of photosystem II photochemistry to be at the same levels as those in unstressed plants; however, the pretreatment did not affect the photosynthetic pigment content. 24-EBL pretreatment clearly alleviated the decrease in leaf osmotic potential under salinity stress. The stress-induced increases in lipid peroxidation and proline contents were not changed under brassinosteroid pretreatment. However, 24-EBL pretreatment increased the peroxidase activity and improved the K+/Na+ ratio in potato leaves, which were likely responsible for the protective 24-EBL action under salt stress.

The effect of polymetallic stress (Mn2+, Cd2+, Cu2+, Ni2+, Zn2+, Pb2+, and Al3+) of different duration and intensity on the endogenous brassinosteroids (BS) content and photochemical activity of photosystem II in barley plants was studied. The content of steroid hormones was determined by a two-stage enzyme immunoassay. It was established for the first time that barley plants responded to polymetallic stress by changing the endogenous content of various phytosteroid groups (24S-methylBS, 24-epiBS, 28-homoBS, B-lactoneBS, and 6-ketoBS). It was shown that the stress-dependent dynamics of changes in the endogenous content of various BS groups is characterized by organ specificity and is determined by the age of plants, the intensity of the acting stressor, and the specificity of brassinosteroids. The observed changes in the endogenous status of BS in barley plants under polymetallic stress are accompanied by inhibition of growth processes, a decrease in the content of the main photosynthetic pigments, and a slight decrease in the efficiency of photochemical processes in PS II (Fv/Fm, ETR, qN, and NPQ). Considering the multifunctional stress-protective effect of brassinosteroids, it is assumed that the change in the endogenous status of BS against the background of polymetallic pollution is adaptive and allows minimizing the damaging effects of toxic heavy metals and aluminum.

We compared the defensive response of rape plants to treatment with 24-epibrassinoldide (10 nM, EBL) before the onset of salt stress (preadaptation stage) and under conditions of chloride salination (150 mM NaCl). It is shown that salt stress inhibits some growth parameters by 30-35%. EBL, regardless of the plant treatment method, showed a pronounced protective effect, first of all, at the level of the assimilating surface, the main photosynthetic pigments, and the photochemical activity of photosystem II. It was established for the first time that the pretreatment of plants with EBL followed by salt stress is accompanied by suppression of NaCl-induced accumulation of proline and an increase in superoxide dismutase activity, whereas the addition of a hormone under salt stress increases the content of carotenoids, which leads to a decrease in the level of lipid peroxidation.

We compared the defensive response of rape plants to treatment with 24-epibrassinoldide (10 nM, EBL) before the onset of salt stress (preadaptation stage) and under conditions of chloride salination (150 mM NaCl). It is shown that salt stress inhibits some growth parameters by 30-35%. EBL, regardless of the plant treatment method, showed a pronounced protective effect, first of all, at the level of the assimilating surface, the main photosynthetic pigments, and the photochemical activity of photosystem II. It was established for the first time that the pretreatment of plants with EBL followed by salt stress is accompanied by suppression of NaCl-induced accumulation of proline and an increase in superoxide dismutase activity, whereas the addition of a hormone under salt stress increases the content of carotenoids, which leads to a decrease in the level of lipid peroxidation.

The endogenous brassinosteroids content in the roots and shoots of early- and mid-season potato microclones was determined. Among the analyzed plant steroid hormones were representatives of brassinolide group, 24-epi- brassinolide group, 28-homobrassinolide group, B-lactones and B-ketons. The level of all brassinosteroids in plant roots exceeded significantly that in shoots, irrespective of the potato term of ripening. Of interest is the fact that in plant shoots there were no BS groups of 24-epibrassinolide. We have first found a relationship between the terms of potato ripening and endogenous content of different BS groups in the aerial and underground plant parts; we have also assessed the age-related changes in the content of BSs, as well as their ratio in the potato plants of the Red Scarlett variety.

Potato plant tolerance to chloride salinity rose after short-term exposure to blue light, which has been first shown in this study. The protective effect of blue light was based on its ability to stimulate the accumulation of low-molecular weight organic compounds with antioxidant activity.

The brassinosteroid (BS) profiles in shoots and roots of the potato plants were shown to be organ-specific and dependent on the term of variety ripening. The amount of all studied groups of steroid phytohormones proved to be an order of magnitude higher in roots than in shoots. In roots, the brassinosteroid lactones predominated, while in shoots, their biogenetic precursors, 6-ketones, were prevailing. The early-ripening variety Zhukovsky Early is characterized by a high content of almost all BS groups (first of all, brassinolide group) and a relatively high content of B-lactones in shoots. With aging, the content of B-lactones in plants decreases, while that of B-ketones grows up.

Physiological mechanisms of canola (Brassica napus L., cv. Westar) plant protection afforded by melatonin (at 0.1–100 μM) from copper salts (at 10–100 μM) were studied. Plants were cultivated on Hoagland–Snyder medium. At the age of 5 weeks, they were subjected to melatonin, copper sulfate, or their combination for 7 days. It was found that excessive copper in a nutrient medium inhibited the dry biomass accumulation against the control by 25–85%. Copper sulfate diminished the content of chlorophylls and carotenoids and functional activity of the thylakoid membranes in the chloroplasts. It increased 2.0–2.5 times the lipid peroxidation (LPO) intensity and the proline level up to 20 times. Melatonin reduced the changes caused by copper, and the degree of the protection depended on melatonin and CuSO4 concentrations. It was found that melatonin decreased the oxidative stress and proline accumulation, both induced by CuSO4. At first, we established the positive correlation (with the coefficient 0.8240) between the level of oxidative stress and proline content in the presence of CuSO4. Possible mechanisms of protection by melatonin and its biological role under conditions of technogenic stress are discussed.

The effect of melatonin on growth parameters, the photochemical activity of photosystem II (PS II), the content of the main photosynthetic pigments, and lipid peroxidation in barley plant leaves under polymetallic stress were studied. Melatonin reduces the toxic effect of polymetals on biomass accumulation, root growth, and maintenance of the assimilating surface. The protective action of the hormone is based on its ability to reduce the intensity of oxidative stress by maintaining the level of carotenoids and increasing the activity of superoxide dismutase, but not by regulating the photochemical activity of chloroplasts. The effectiveness of melatonin does not depend on the duration of exposure. The data obtained can be the basis for optimizing the use of melatonin as a plant priming inducer.

Endophytic entomopathogenic fungi are promising agents for the promotion of plant growth, the activation of immunity, and protection against phytopathogens. However, physiological changes in plants after treatment with fungi are insufficiently studied. We investigated the effect of potato inoculation with conidia from Metarhizium robertsii and Beauveria bassiana on the growth (fresh and dry weight, length of shoots and roots, counts of stolons and leaves, and total surface area of leaves) and physiological parameters (pigment contents, free proline and malondialdehyde content, and activity of antioxidant enzymes) at the initial stage of the plant–fungus interaction (seven days) under hydroponic conditions. The results showed that the fungi could act as an immune-modulating factor for plants based on the increase in malondialdehyde and proline contents. At the same time, we observed growth retardation and a decrease in the content of photosynthetic pigments, which may be caused by a tradeoff between plant growth and the immune response.

The approaches are identified that increase the survival rate of honeysuckle microclones in the process of adaptation to ex virto conditions up to 98%.

The microclones of potato (variety Lugovskoy) were grown on the modified Murashige-Skoog (MS) agar medium in the absence (control) or presence of JA at concentrations of 0.001, 0.1, and 10 µM. We evaluated plant growth parameters such as the length of the axial organs, the number of stolons, leaves, the area of the assimilating surface, and the wet and dry mass of aboveground and underground organs. For the first time, has been demonstrated, that jasmonic acid (0.1 and 10 µM) was showed a pronounced growth-stimulating effect on potato plants.

We investigated the effect of 125 mM NaCl on the potato leaves photosynthetic parameters (the content of chlorophylls a, b, and carotenoids; photochemical activity of photosystem II).

Melatonin supports the photochemical activity of photosystem II (PS II) and slows down the degradation of the main photosynthetic pigments during aging of leaves of monocotyledonous plants. The protective effect of melatonin is manifested in an increase in the maximum (F

Under study is a conjugate boundary value problemdescribing a joint motion of a binary mixture and a viscous heat-conducting liquid in a two-dimensional channel, where the horizontal component of the velocity vector depends linearly on one of the coordinates. The problemis nonlinear and inverse because the systems of equations contain the unknown time functions—the pressure gradients in the layers. In the case of small Marangoni numbers (the so-called creeping flow) the problem becomes linear. For its solutions the two different integral identities are valid which allow us to obtain a priori estimates of the solution in the uniform metric. It is proved that if the temperature on the channel walls stabilizes with time then, as time increases, the solution of the nonstationary problem tends to a stationary solution by an exponential law.

The mechanisms of potato (Solanum tuberosum L.) plants’ tolerance to chloride salinity were investigated in cv. Lugovskoi regionalized in Russia. Regenerated plants were produced in vitro from apical meristem and grown on half-strength Murashige and Skoog medium (0.5 MS) using a hydroponic unit in controlled-climate conditions. At the age of six weeks, the plants were exposed to salt stress (50–150 mM NaCl, 7 days). Plant response to salt stress was estimated by growth parameters (fresh and dry biomass of the aboveground and underground parts of plants, linear dimensions of shoot and root, area of leaf surface, and number of stolons) and physiological characteristics (level of photosynthetic pigments, accumulation of sodium, potassium, and calcium ions in the aboveground and underground parts of plants, content of proline, activity of antioxidant enzymes, plant tissue hydration, osmotic potential, and POL). It was found that, in response to salinity, the plants of potato, cv. Lugovskoi, showed a considerable inhibition of growth processes, reduction in chlorophyll a content, and suppression of stolon formation, which points to a rather low salinity tolerance of the cultivar. At the same time, under weak or moderate salt stress, the plants preserved water homeostasis owing to effective osmoregulation, actively accumulated proline that acted as a stress protector, and showed hardly any signs of oxidative stress. It was assumed that low salt tolerance of this cultivar depends on the inability of its root system to retain sodium ions and ensure selective ion transport to the aboveground part of the plant and on inefficiency of the system of sodium ions’ removal from the cytoplasm of leaf cells and their compartmentalization in the central vacuole with the purpose of reducing their toxic effect. The obtained results may be useful for working out a technique of improving salt tolerance of this cultivar by the methods of molecular genetics.

The protective effect of jasmonic acid (JA) was evaluated under the stress conditions (100 mM NaCl). The potato plants Solanum tuberosum L, mid-season variety Lugovskoy, were used in the experiments. The plant-regenerants were grafted and grown in test tubes on the modified Murashige and Skoog agar medium in the absence (control) or presence of JA at concentrations of 0.001, 0.1, and 10 μM under the optimal conditions or with addition of NaCl. After 28 days of cultivation, the growth (stem and root lengths, tier and leaf numbers, and plant mass) and physiological (proline and photosynthetic pigment contents and teh osmotic potential of cell exudate) characteristics of the plants were assessed. Jasmonic acid (0.1 and 10 μM) has been demonstrated to display a pronounced protective effect on potato plants under the salt stress condition. JA abolished partially the negative salt effect on the main photosynthetic pigments and maintained the cell osmotic status during salinization.

This is the first study to show that brief pretreatment of potato plants with two brassinosteroids differing in structure causes in plants the ability to react to delayed salt stress by accumulation of compounds with antioxidant activity and by increased salt tolerance.

The ability of brassinosteroids, such as 24-epibrassinolide (EBL) to increase the resistance of oilseed rape plants (Brassica napus L.) to salt stress (175 mM NaCl) was investigated along with the possible mechanisms of their protective action. Seedlings were grown for three weeks on the Hoagland-Snyder medium under controlled conditions. The experimental plants were treated with either (1) 175 mM NaCl, or (2) 10−10 M EBL, or (3) 175 mM NaCl plus 10−10 M EBL by adding the corresponding components to the growth medium. The exposure was 7 and 14 days. As compared to the control, salinization inhibited plant height by 33–35%, reduced leaf area by 2.0–2.5 times, reduced 2.5- and 2-fold plant fresh and dry weight, respectively, reduced water content of plant tissues by 26–31% and, twofold, the content of chlorophylls a and b. Plants responded to NaCl by developing oxidative stress conditions, lowering the osmotic potential of the cell contents down to −2 MPa, accumulating proline (by 43–52 times) and low-molecular-weight phenolics (by 1.9–2.7 times). Oilseed rape plants were shown to respond to salinization with an increase of endogenous content of steroid hormones: 24-epibrassinosteroids (24-epibrassinolide and 24-epicastasterone), 24S-methyl-brassinosteroids (brassinolide and castasterone), and 28-homobrassinosteroids (28-homobrassinolide and 28-homocastasterone); such evidence indirectly confirms the involvement of brassinosteroids in the development of salt tolerance. Adding EBL to the nutrient medium under optimal growth conditions did not significantly affect the indices under study. Under salt stress, EBL showed a pronounced protective effect: stem growth was fully restored, plant assimilation area increased by as much as 67–76% as compared to the control index, fresh and dry weight largely recovered (up to 85–92% of the control values), and the inhibitory effect of NaCl on photosynthetic pigments was diminished. Exogenous EBL impeded the development of NaCl-dependent lipid peroxidation and increased the osmotic potential of the leaf cell contents. The protective effect of EBL under salt stress was probably associated with EBL antioxidant effect, rather than the hormone-induced accumulation of proline and of low-molecula-weight phenolics, as well as with the ability to regulate water status by maintaining intracellular ion homeostasis.

Transgenic Arabidopsis thaliana plants carrying the GUS reporter gene fused to the promoter of the gene of primary response to cytokinins (CKs), ARR5, were used to estimate the influence of several brassinosteroids (BRs): brassinolide (BL), epibrassinolide (EBL), homobrassinolide (HBL), and 6-o-carboxymethyloxohomocastasterone (CHC) on the expression of CK signalling genes. BRs tested differed in their ability to activate the ARR5 gene promoter in 4-day-old seedlings and 3-week-old plants. BL caused the most prominent effect, yet it was considerably less than that of 6-benzylaminopurine (BA). An increase in GUS activity was observed in both dark and light conditions; however, the rate of elevation was higher in dark conditions. The activation of the PARR5:GUS fusion was accompanied by a moderate induction of the PAHK:GUS constructs, in which the reporter GUS gene was fused to the promoter of one of the CK receptor histidine kinases. The effects of BL on the AHK gene promoters were organ specific and correlated with the ability of a particular AHK gene to respond to BA treatment. BL activated the AHK3 promoter in 4-day-old seedlings and in shoots and roots of 3-week-old plants without any effect in detached leaves. The AHK2 gene promoter was activated by BA and BL only in seedlings, whereas the AHK4 gene promoter was activated only in roots. BL treatment caused the coordinate elevation of the CK levels in leaves to the same degree as the activation of the PAHK:GUS construct, suggesting that the accumulation of CKs was the reason for the activation by BRs of the CK signalling genes. The data obtained provide the evidence for the involvement of BRs in the regulation of the genes of the CK signalling pathway through an increase in the CK levels. However, the exact molecular mechanisms underlying BR-induced elevation of the CK content are unclear and warrant identification in the future.

In order to evaluate whether brassinosteroids (BS) and green light regulate the transcription of plastid genes in a cross-talk with cytokinins (CKs), transcription rates of 12 plastid genes (ndhF, rrn23, rpoB, psaA, psaB, rrn16, psbA, psbD, psbK, rbcL, atpB, and trnE/trnY) as well as the accumulation of transcripts of some photoreceptors (PHYA, CRY2, CRY1A, and CRY1B) and signaling (SERK and CAS) genes were followed in detached etiolated barley leaves exposed to darkness, green or white light ±1μm 24-epibrassinolide (EBL). EBL in the dark was shown to up-regulate the transcription of 12 plastid genes, while green light activated 10 genes and the EBL combined with the green light affected the transcription of only two genes (psaB and rpoB). Green light inhibited the expression of photoreceptor genes, except for CRY1A. Under the green light, EBL practically did not affect the expression of CRY1A, CAS and SERK genes, but it reduced the influence of white light on the accumulation of CAS, CRY1A, CRY1B, and SERK gene transcripts. The total content of BS in the dark and under white light remained largely unchanged, while under green light the total content of BRs (brassinolide, castasterone, and 6-deoxocastasterone) and HBRs (28-homobrassinolide, 28-homocastasterone, and 6-deoxo-28-homocastasterone) increased. The EBL-dependent up-regulation of plastome transcription in the dark was accompanied by a significant decrease in CK deactivation by O-glucosylation. However, no significant effect on the content of active CKs was detected. EBL combined with green light moderately increased the contents of trans-zeatin and isopentenyladenine, but had a negative effect on cis-zeatin. The most significant promotive effect of EBL on active CK bases was observed in white light. The data obtained suggest the involvement of CKs in the BS- and light-dependent transcription regulation of plastid genes.

Comparative analysis of growth characteristics, content of auxins and cytokinins, and the level of photosynthetic pigments was conducted in det2 mutant plants of Arabidopsis thaliana (L.) Heynh notable for a disturbed synthesis of brassinosteroids and therefore their low endogenous level. In this mutant line, we observed de-etiolation: the formation of large cotyledons and long hypocotyls in the dark already shown earlier. For the first time, we analyzed transcription of 12 chloroplast genes encoding functionally different proteins and RNAs in rosette leaves of wild type and det2 plants. In rosette leaves of mutant plants, transcription activity of the investigated plastid genes was much higher than in the parental line. On these grounds, we assumed that the low level of brassinosteroids was correlated with the activation of transcription of some chloroplastic genes and realization of the de-etiolation program.

The regulatory role of more active brassinosteroids - brassinolide in seedling development in darkness was studied. The growth parameters and photosynthetic pigment content of Arabidopsis thaliana seedlings under differ light conditions were investigated. The plant model to study regulatory role of selective light and brassinosteroids are Arabidopsis thaliana. A. thaliana ecotype Columbia (Col) and det2 mutant with disturbed synthesis of brassinolide were used. The plant grow parameters depending on the brassinolide concentration. Physiological activity of green light also blue light in the regulation of Arabidopsis seedling development was noted. The interaction between plant development program - skoto- or photomorphogenesis and endogenous level of brassinosteroids has been shown.

The effects of blue light (BL) and jasmonic acid (JA) on morphogenesis of Arabidopsis thaliana (L.) Heynh seedlings of genotypes Col and Ler and their mutants, namely, axr1-3 and jar1-1 mutants resistant to IAA and JA, respectively, and a CRY1 photoreceptor-deficient mutant hy4 were studied. Both 1 μM JA and BL exposure retarded hypocotyl growth of Ler, Col, and jar1-1 seedlings, whereas JA had no effect on hypocotyl growth of axr1-3, but the suppression of hypocotyl growth of this mutant by BL was even more noticeable than that of Ler, Col, and jar1-1. JA and BL applied simultaneously inhibited hypocotyl growth of axr1-3 and especially of Ler, Col, and jar1-1 more than either of factors applied separately. The hy4 mutant did not respond to BL, whereas JA stimulated its hypocotyl growth. JA did not change the cotyledon size of Col, axr1-3, and jar1-1 and reduced the cotyledon size of Ler and hy4. BL enhanced the cotyledon growth of all wild-type and mutant plants used in the study. The cotyledon sizes of all plants except Ler were also increased when JA and BL were applied together. Some of the growth responses correlated with the endogenous IAA and ABA contents. Thus, for example, the hypocotyl and cotyledon growth retardation of Ler seedlings in the presence of JA correlated with a reduced level of free IAA and a considerable increase in the free ABA level in plants grown both in darkness and in BL. Under other growth conditions, no correlation between the endogenous IAA and ABA levels and A. thaliana seedling growth was noted. The interaction between the signal transduction pathways triggered by BL and JA at the early stages of arabidopsis morphogenesis is discussed on the basis of Col, Ler, axr1-3, and jar1-1 hypocotyl growth responses.

The effects of blue light (BL), green light (GL), and red light (RL) on morphogenesis photoregulation of transgenic tobacco (Nicotiana tabacum L.) plants containing a copy of human interleukin-18 gene were studied. Wild-type and transgenic (Il1 No.87–1 and Il18 No.7–11) lines and derived calluses were used. Photomorphogenesis of transgenic lines under GL and RL differed substantially from that of initial line at early stages of morphogenesis; this was expressed in hypocotyl lengthening under GL and cotyledon enhanced expansion under RL. Growth responses to light quality were related to changes in the levels of zeatin, IAA, and ABA. Thus, hypocotyl lengthening and increased cotyledon area under GL occurred at the elevated level of IAA and reduced level of ABA. Growth of callus cells in transgenic lines during zero passage differed from wild-type calluses only in darkness. The data obtained indicate that tobacco plant transformation with the human interleukin-18 gene changed functioning of the photoregulation systems at early developmental stages. This phenomenon is evidently explained by the pleiotropic effects of the gene inserted.

The effects of low intensity red luminescent radiation emitted by the polyethylene light-correcting film due to the conversion of UV-A radiation on Arabidopsis thaliana (L.) Heynh. morphogenesis and hormonal balance were studied. Wild-type Ler plants and two mutants, hy3 and hy4, displaying disturbances in the synthesis of phytochrome B and cryptochrome 1, respectively, were compared. In wild-type and hy4 plants grown under the light-correcting film, growth and development were substantially accelerated, whereas, in hy3 plants, they were retarded. These changes were correlated with changes in the levels of endogenous hormones, both growth activators and inhibitors. We concluded that low intensity red luminescent radiation affected the plant hormonal balance. In its turn, the changes in the hormone ratios, growth stimulators and inhibitors, affected the rate of plant growth and their productivity.

We studied the effect of 24-epibrassinolide (EB) on the levels of endogenous hormones and photomorphogenesis of Arabidopsis thaliana (L.) Heynh wild-type (Ler) and mutant (hy4) seedlings. This mutant is deficient in the cryptochrome 1 (CRY1) synthesis. CRY1, which is a product of the HY4 gene, is a blue light photoreceptor in wild-type plants, but is sensitive to green light as well. In dark-grown seven-day-old mutant seedlings, the ABA/zeatin ratio differed from this ratio in wild-type seedlings. Thehy4 mutant exhibited a lower zeatin and higher free-ABA contents, which could retard its hypocotyl growth in darkness. EB retarded the growth of hypocotyls in etiolated hy4 seedlings and enlarged their cotyledons more efficiently than in wild-type seedlings. Green light (GL) did not affect the growth of hypocotyls but enlarged cotyledons of hy4 seedlings, which might be associated with some increase in the level of free IAA and a considerable decrease in free ABA and also with a decrease in the cytokinin level in seedlings. The hy4 cotyledon response to GL depended evidently on photoreceptors other than CRY1. GL enhanced the effects of EB on the morphogenesis of both Ler and hy4 seedlings, which was coupled with changes in the balance of endogenous IAA, ABA, and cytokinins. We may suppose that EB is involved in the control of photomorphogenesis by interaction with endogenous hormones, which are involved in the transduction of a light signal absorbed by the GL photoreceptors.

Light is a key environmental factor regulating the growth and development of plants. The regulatory and photosynthetic roles of light depend on its intensity and spectral composition. The red and blue spectral regions are characterized by a high physiological activity [1]. Many researchers consider green light to be rather inactive part of solar radiation. This point of view is based mainly on the fact that the leaves of the majority of plants are green and, therefore, plants rather reflect green light than use it as a source of energy. However, some studies of Russian and foreign researchers revealed a special regulatory role of green light. It is obvious that the ratio between different wavelengths of the incident light flux serves as a signal initiating one or another development program and determines the light adaptation of plants. An impor� tant role of the ratio between green and farred light in the manifestation of the shadow avoidance syndrome was shown in 1952 by Borthwick [2], whereas the same effect determined by the balance between green and blue light was revealed only two years ago by Sellaro et al. [3] and Zhang et al. [4].

Development of semi-finished products manufactured from alpha +beta titanium alloys has necessitated a thorough study of the interrelation between the structure and phase composition of these alloys, and their mechanical properties. For the necessary combination of mechanical properties to be assured, semi-finished products manufactured from titanium alloys must have a homogeneous macrostructure and a fine-grained microstructure. The structure of semiproducts from alpha+beta alloys is determined by their thermomechanical deformation behaviour.