Phytohormones

Abiotic stresses including salinity, drought, extreme temperatures, and heavy metals are posing serious threats to agricultural yields as well as the quality of produce. This necessitates the production of cultivars capable to withstand the harsh environmental conditions without substantial yield losses. Owing to the complexity underlying stress tolerance traits, conventional breeding techniques have met with limited success and demand effective supplements to feed the growing food demands worldwide. This necessitates the development and deployment of novel and potent approaches, and engineering of phytohormone metabolism could be a method of choice to produce climate resilient crops with higher yields. Phytohormones are considered critical for regulating and coordinating plant growth and development; however, in recent years, they have received great attention for their multifunctional roles in plant responses to environmental stimuli. Creditable research has shown that phytohormon...

Coconut water (coconut liquid endosperm), with its many applications, is one of the world's most versatile natural product. This refreshing beverage is consumed worldwide as it is nutritious and beneficial for health. There is increasing scientific evidence that supports the role of coconut water in health and medicinal applications. Coconut water is traditionally used as a growth supplement in plant tissue culture/micropropagation. The wide applications of coconut water can be justified by its unique chemical composition of sugars, vitamins, minerals, amino acids and phytohormones. This review attempts to summarise and evaluate the chemical composition and biological properties of coconut water.

This is a short review of the classical and new, natural and synthetic plant hormones and growth regulators (phytohormones) and highlights some of their uses in plant tissue culture. Plant hormones rarely act alone, and for most processes-at least those that are observed at the organ level--many of these regulators have interacted in order to produce the final effect. The following substances are discussed: (a) Classical plant hormones (auxins, cytokinins, gibberellins, abscisic acid, ethylene) and growth regulatory substances with similar biological effects. New, naturally occurring substances in these categories are still being discovered. At the same time, novel structurally related compounds are constantly being synthesized. There are also many new but chemically unrelated compounds with similar hormone-like activity being produced. A better knowledge of the uptake, transport, metabolism, and mode of action of phytohormones and the appearance of chemicals that inhibit synthesis, transport, and action of the native plant hormones has increased our knowledge of the role of these hormones in growth and development. (b) More recently discovered natural growth substances that have phytohormonal-like regulatory roles (polyamines, oligosaccharins, salicylates, jasmonates, sterols, brassinosteroids, dehydrodiconiferyl alcohol glucosides, turgorins, systemin, unrelated natural stimulators and inhibitors), as well as myoinositol. Many of these growth active substances have not yet been examined in relation to growth and organized development in vitro.

20-hydroxyecdysone (20E) is the major phytoecdysteroid of about 6% of plants. Its role in plant physiology has not been fully elucidated. In this work we studied the effects of 20E application on some morphological and biochemical parameters of tomato, Lycopersicum esculentum, seed during germination and seedling development (5 d). We compared the 20E effects with the action of phytohormones: gibberellic acid (GA 3), naftalen acetic acid (NAA), benzyl amino purine (BAP). NAA treatment resulted in marked reduction in shoot length. GA 3 treatment promoted maximal shoot elongation. BAP affected negatively shoot length only at late stages, while 20E application stimulated shoot elongation at early stages and reduced it on the fifth day; NAA inhibited root elongation all along the test period. GA 3 treatment had no effect on root length, whereas BAP showed strong inhibition on root elongation. On the other hand, 20E showed a weak inhibition of root elongation on the fifth day. As compared to control and to other treatments, NAA and 20E provoked a drastic decrease in protein contents during seedling growth, whereas a high increase was observed under BAP treatment. Electrophoresis revealed that protein bands were not degraded and mobilized after NAA treatment while in control or after 20E and others phytohormones applications, protein patters displayed weak band intensities and some of them were not detected. NAA, GA 3 and BAP provoked a decrease in proline content during seedlings, while the effect of 20E on proline levels varied during germination and plantlet development. This work showed that 20E like phytohormones fulfil some bioactive actions during germination and seedlings growth in tomato.

The modern agriculture is based on the intensive technologies of plant cultivation using phytohormones and their synthetic analogues to regulate the genetic program of plant growth and development during ontogenesis, increase their yield and improve theagricultural product quality, as well as increase the plant resistance to adverse environmental factors and pathogens. The very promising approach is the creation of new plant growth regulators based on low molecular weight synthetic heterocyclic compounds, derivatives of pyrazolotriazinones having phytohormone-like growth regulating activity. The main aim of our work was to study the stimulating effect of low molecular weight heterocyclic compounds, derivatives of pyrazolotriazinones synthesized at the Institute of Bioorga-nic Chemistry and Petrochemistry of the National Academy of Sciences of Ukraine, on growth and development of barley (Hordeum vulgare L.) cultivar Commandor during the vegetation period. The conducted researchers showed that the chemical compounds, derivatives of pyrazolotriazinones used at the concentration 10-9M exhibited stimulating activity on seed germination and vegetative growth of 21st-day-old barley seedlings; their activity was similar or exceeded the activity of the phytohormones auxins IAA, NAA and Kinetin used at the same concentration 10-9M. The biometric indices of the 21st-day-old barley seedlings grown on the water solution of the chemical heterocyclic compounds, derivatives of pyrazolotriazinones used in the concentration of 10-9M were similar or higher of the biometric indices of the control barley seedlings grown on the distilled water or barley seedlings grown on the water solution of auxins IAA, NAA and Kinetin used at the same concentration 10-9M in average: at the 11-26 % - by the length of seedlings and at the 21-130 % - by the length of the roots. The obtained results showed also that the testedchemical heterocyclic compounds, derivatives of pyrazolotriazinonesused at the concentration 10-9M stimulated the synthesis of photosynthetic pigments in the leaves of 21th-day-old barley seedlings, which, as is known, play a key role in photosynthetic processes and photoprotection in plants, and provide plant productivity. The content of chlorophyll a in the leaves of 21th-day-old seedlings of barley increased in average: at the 7-13 %; the content of chlorophyll b increased in average: at the 5-19 % ; the content of chlorophylls a+b increased in average: 6-15 %; the content of chlorophylls a/b increased in average: 6-10 %;the content of carotenoids increased in average: at the 10-19 %, as compared with similar indices of barley seedlings grown either on the distilled water (control), or water solution of IAA, NAA, and Kinetin, respectively. The obtained results confirmed the possibility of the application in the agricultural practice of derivatives of pyrazolotriazinonesused at the concentration 10-9M to improve the growth and development of barley (Hordeum vulgareL.) cultivar Commandor during the vegetation period.

Por sus múltiples interrelaciones, la visión de los cultivos recuerda un ecosistema, tanto más cuando se aplican las técnicas de control y manejo integrado. Y es lógico que así ocurra, ya que basta considerar que los cultivos son vegetales domesticados que, aunque protegidos por el hombre, deben seguir conviviendo con formas silvestres.

Es opinión personal que el futuro forzará un manejo agrícola más comprometido con el medio natural, integrado en este. Ello puede ser inconveniente para el consumidor que demanda fruta de aspecto perfecto, pero creo que a largo plazo debe buscarse sostenibilidad de la actividad agrícola y no la máxima producción de fruta inmaculada, pero con frecuencia insípida, por metro cuadrado. Esto requiere un mayor conocimiento del medio, pero también comporta mayor economía de la producción.

La población mundial no parece que vaya a estabilizarse al nivel actual, tanto menos en una cifra inferior. Si bien las técnicas y los recursos bien utilizados pueden dar alimento a una población mayor que la actual, el problema a resolver es la calidad de vida resultante del esfuerzo productivo, especialmente el agrícola. Calidad de vida estrechamente relacionada con la creciente alteración de los intrincados ciclos naturales, debido a la presión sobre el medio ambiente.

Sumada a un cambio climático global, la presión sobre el medio natural fue el origen de la desaparición de las civilizaciones Mesopotámica y del Valle del Indo, por ejemplo. Desde aquel tiempo hemos avanzado mucho técnicamente, pero no por ello se deja de producir sin previsión, agotando acuíferos, desforestando las cabeceras y márgenes de los ríos, descuidando la diversidad genética, utilizando plaguicidas y fertilizantes sin control adecuado, destruyendo zonas naturales de interés, permitiendo que en un crecimiento no planificado las ciudades sepulten las mejores tierras de cultivo, etc. Ha llegado el momento de la previsión a largo plazo, en definitiva del futuro sostenible.

Por sus múltiples interrelaciones, la visión de los cultivos recuerda un ecosistema, tanto más cuando se aplican las técnicas de control y manejo integrado. Y es lógico que así ocurra, ya que basta considerar que los cultivos son vegetales domesticados que, aunque protegidos por el hombre, deben seguir conviviendo con formas silvestres.

Es opinión personal que el futuro forzará un manejo agrícola más comprometido con el medio natural, integrado en este. Ello puede ser inconveniente para el consumidor que demanda fruta de aspecto perfecto, pero creo que a largo plazo debe buscarse sostenibilidad de la actividad agrícola y no la máxima producción de fruta inmaculada, pero con frecuencia insípida, por metro cuadrado. Esto requiere un mayor conocimiento del medio, pero también comporta mayor economía de la producción.

La población mundial no parece que vaya a estabilizarse al nivel actual, tanto menos en una cifra inferior. Si bien las técnicas y los recursos bien utilizados pueden dar alimento a una población mayor que la actual, el problema a resolver es la calidad de vida resultante del esfuerzo productivo, especialmente el agrícola. Calidad de vida estrechamente relacionada con la creciente alteración de los intrincados ciclos naturales, debido a la presión sobre el medio ambiente.

Sumada a un cambio climático global, la presión sobre el medio natural fue el origen de la desaparición de las civilizaciones Mesopotámica y del Valle del Indo, por ejemplo. Desde aquel tiempo hemos avanzado mucho técnicamente, pero no por ello se deja de producir sin previsión, agotando acuíferos, desforestando las cabeceras y márgenes de los ríos, descuidando la diversidad genética, utilizando plaguicidas y fertilizantes sin control adecuado, destruyendo zonas naturales de interés, permitiendo que en un crecimiento no planificado las ciudades sepulten las mejores tierras de cultivo, etc. Ha llegado el momento de la previsión a largo plazo, en definitiva del futuro sostenible.

The recent innovation strategy used in the modern agricultural biotechnology is an elaboration of new effective and ecologically safe plant growth regulating substances on the base of synthetic low molecular weight five and six-membered heterocyclic compounds derivatives of pyridine, pyrimidine, pyrazole, oxazole, and isoflavones as an effective substitutes of phytohormones and traditional plant growth regulators to develop agricultural crops with genetically improved commercially important traits such as accelerated growth and development, increased plant productivity and improved quality of production, and enhanced plant tolerance to abiotic stress factors such as drought, salinity, heat, chilling, osmotic stress, soil pollution by anthropogenic factors, and to biotic stress factors such as pathogens and pests [1]. Maize (Zea mays L.) is ancient cereal crop traditionally used as source for dietary food and pharmaceutical industry due to high content of nutrients such as lipids, proteins, carbohydrates, vitamins, dietary fiber and biological active compounds in the seed and seed oil, and as raw material for the biofuel industry and animal feed [2]. Our work was aimed to study of plant growth regulating activity of new synthetic low molecular weight heterocyclic compounds phosphorylated derivatives of oxazole and pyrimidine with perspective their application as a new effective substitutes of phytohormones for improving of cultivation of maize (Zea mays L.) hybrid Palmyra FAO 190. The conducted in the laboratory conditions researches showed high growth stimulating auxin-like effect of tested chemical compounds on germination of seeds, growth and development of maize seedlings during the vegetation. The comparative statistical analysis showed that the biometric indexes of 14th-day-old seedlings of maize grown on the water solution of heterocyclic compounds used at concentration 10-9M were higher than the biometric indexes of 21st-day-old seedlings of maize grown either on the distilled water (control) or on the water solution of auxins IAA and NAA used at the same concentration 10-9M in average: at the 23 % - by total length of seedlings, 5-37 % - by total length of roots, and at the 7-87 % - by total number of roots. The positive effect of some from tested chemical heterocyclic compounds on increase of synthesis of photosynthetic pigments in the leaves of 14th-day-old seedlings of maize was also found: the content of chlorophyll a was increased in average at the 5-10 %; the content of chlorophyll b was increased in average at the 10-74 %; the content of chlorophylls a+b was increased in average at the 5-11 %. The practical application in the agricultural biotechnology of synthetic low molecular weight heterocyclic compounds phosphorylated derivatives of oxazole and pyrimidine as new effective substitutes of phytohormones for improving of growth and development of maize (Zea mays L.) hybrid Palmyra FAO 190 was proposed.
1. V. Tsygankova, Y. Andrusevich, O. Shtompel, O. Myroljubov, A. Hurenko, R. Solomyanny, G. Mrug, M. Frasinyuk, O. Shablykin, V. Brovarets. Study of Auxin, Cytokinin and Gibberellin-like Activity of Heterocyclic Compounds Derivatives of Pyrimidine, Pyridine, Pyrazole and Isoflavones. European Journal of Biotechnology and Bioscience, 2016, 4(12): 29-44.
2. Shah T.R., Prasad K., Kumar P. Maize-A potential source of human nutrition and health: A review. Cogent Food & Agriculture. 2016, 2: 1166995.

Abiotic stress is a primary threat to fulfill the demand of agricultural production to feed the world in coming decades. Plants reduce growth and development process during stress conditions, which ultimately affect the yield. In stress conditions, plants develop various stress mechanism to face the magnitude of stress challenges, although that is not enough to protect them. Therefore, many strategies have been used to produce abiotic stress tolerance crop plants, among them, abscisic acid (ABA) phytohormone engineering could be one of the methods of choice. ABA is an isoprenoid phytohormone, which regulates various physiological processes ranging from stomatal opening to protein storage and provides adaptation to many stresses like drought, salt, and cold stresses. ABA is also called an important messenger that acts as the signaling mediator for regulating the adaptive response of plants to different environmental stress conditions. In this review, we will discuss the role of ABA in response to abiotic stress at the molecular level and ABA signaling. The review also deals with the effect of ABA in respect to gene expression.

Abiotic stresses including salinity, drought, extreme temperatures, and heavy metals are posing serious threats to agricultural yields as well as the quality of produce. This necessitates the production of cultivars capable to withstand the harsh environmental conditions without substantial yield losses. Owing to the complexity underlying stress tolerance traits, conventional breeding techniques have met with limited success and demand effective supplements to feed the growing food demands worldwide. This necessitates the development and deployment of novel and potent approaches, and engineering of phytohormone metabolism could be a method of choice to produce climate resilient crops with higher yields. Phytohormones are considered critical for regulating and coordinating plant growth and development; however, in recent years, they have received great attention for their multifunctional roles in plant responses to environmental stimuli. Creditable research has shown that phytohormones including the classical ones – auxins, cyto-kinins, ethylene, gibberellins, and newer members including brassinosteroids, jas-monates, and strigolactones – may prove to be potent targets for their metabolic engineering for producing abiotic stress-tolerant crop plants. This chapter presents short description of the roles of phytohormones in abiotic stress responses and tolerance followed by reviewing attempts made by the plant biotechnologists for

Coconut water (coconut liquid endosperm), with its many applications, is one of the world's most versatile natural product. This refreshing beverage is consumed worldwide as it is nutritious and beneficial for health. There is increasing scientific evidence that supports the role of coconut water in health and medicinal applications. Coconut water is traditionally used as a growth supplement in plant tissue culture/micropropagation. The wide applications of coconut water can be justified by its unique chemical composition of sugars, vitamins, minerals, amino acids and phytohormones. This review attempts to summarise and evaluate the chemical composition and biological properties of coconut water.

Endophytic bacteria colonize plants and live inside them for part of or throughout their life without causing any harm or disease to their hosts. The symbiotic relationship improves the physiology, fitness, and metabolite profile of the plants, while the plants provide food and shelter for the bacteria. The bacteria-induced alterations of the plants offer many possibilities for biotechnological, medicinal, and agricultural applications. The endophytes promote plant growth and fitness through the production of phytohormones or biofertilizers, or by alleviating abiotic and biotic stress tolerance. Strengthening of the plant immune system and suppression of disease are associated with the production of novel antibiotics, secondary metabolites, siderophores, and fertilizers such as nitrogenous or other industrially interesting chemical compounds. Endophytic bacteria can be used for phytoremediation of environmental pollutants or the control of fungal diseases by the production of lytic ...

xyloglucan-specific α-1,2and α-1,6-fucosyltransferases and glycosyltransferases, CSL genes of xyloglucan glucan synthases and β-1,4-mannan synthases, MUR genes xyloglucan galactosyltransferases as well as the AtXT1 gene and homologous AtGT2-7 genes xyloglucan xylosyltransferases at Arabidopsis; the XS1 gene of xylan synthase at rice, and also GS1 gene of glucan synthase at corn. A possible role of cell wall protein -extensin (encoded by the auxinregulated HRGP gene) in the plants defence from pathogens and unfavourable factors of external environment is discussed .

The pattern of changes in some phytohormones content and oxidoreductive processes during seed germination of two lupin species was studied. During radicle protrusion (day 2), the amount of cytokinins in narrow-leafed lupin seeds greatly increased in both radicles and cotyledons, and it was accompanied with a huge drop in abscisic acid. In white lupin seeds, the increase in cytokinin was noticed only in the radicles, and the decrease in abscisic acid in the cotyledons. Both alterations, as well as the generation of superoxide radical (O2•¯) occurred to the lesser extent than in the narrow-leafed lupin cotyledons suggesting a cross-talk between the cytokinin and O2•¯ promoting germination, which was faster in the case of the narrow-leafed lupin. When the hypocotyls elongated (day 5), O2•¯ was detectable more in the radicles than in the cotyledons, and mostly in the elongation zone, in seedlings of both species. While sugar and protein were utilized by the growing seedlings, catalase and ascorbate peroxidase activities dropped by 25-50%, but non-specific peroxidase (POX) activity highly (several-fold) increased indicating regulatory role of POX in seedling development of both lupin species. From the methodological point of view it should be emphasised that the specific enzymatic activity of germinating seeds cannot be the only expression of the activity, because huge alterations in the protein content can change the final result.
Keywords: abscisic acid, antioxidative enzymes, germination, H2O2, legume, lupin, ROS, seedling.

An efficient protocol has been developed for regeneration of Lepidium sativumplantlets using shoot tip, cotyledonary leaf and internodes as explants. Proliferation of shoots was achieved on MS medium supplemented with various concentrations of IAA with BAP alone or kinetin MS medium with BAP (5.0mg/l + IAA (2.0mg/l) was optimum for inducing the maximum number of shoots from shoot tip (6.55) followed by cotyledonary leaves (4.45) and internode (0.60). Hundred percent callusing was achieved on MS medium supplemented with 2, 4-D (1.0, 1.5&2.0 mg/l) along with kinetin (1.0mg/l& 0.5mg/l), respectively.MS medium having 2, 4-D (1.0 mg/l and 1.5 mg/l in combination with BAP (1.0mg/l &1.5mg/l), respectively also showed 100% callusing for shoot tip and cotyledonary leaves. The best rooting media were with [IAA(2.0 mg/l) + BAP (5.0 mg/l&2.0 mg/l),) and IAA (2.0 mg/land 3.0 mg/l + kinetin (0.5 mg/l)].  Rooted plantlets were transferred to thermocol cups filled with a mixture of soil and sand (3:1). The rooted seedlings were acclimatized to soil conditions with 80% survival rate. 

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This is a short review of the classical and new, natural and synthetic plant hormones and growth regulators (phytohormones) and highlights some of their uses in plant tissue culture. Plant hormones rarely act alone, and for most processes-at least those that are observed at the organ level--many of these regulators have interacted in order to produce the final effect. The following substances are discussed: (a) Classical plant hormones (auxins, cytokinins, gibberellins, abscisic acid, ethylene) and growth regulatory substances with similar biological effects. New, naturally occurring substances in these categories are still being discovered. At the same time, novel structurally related compounds are constantly being synthesized. There are also many new but chemically unrelated compounds with similar hormone-like activity being produced. A better knowledge of the uptake, transport, metabolism, and mode of action of phytohormones and the appearance of chemicals that inhibit synthesis, transport, and action of the native plant hormones has increased our knowledge of the role of these hormones in growth and development. (b) More recently discovered natural growth substances that have phytohormonal-like regulatory roles (polyamines, oligosaccharins, salicylates, jasmonates, sterols, brassinosteroids, dehydrodiconiferyl alcohol glucosides, turgorins, systemin, unrelated natural stimulators and inhibitors), as well as myoinositol. Many of these growth active substances have not yet been examined in relation to growth and organized development in vitro.

Brassinosteroids (BRs) are ubiquitous plant steroid hormones, playing diverse roles in plant growth, development and stress responses. Defects in BRs biosynthesis or signaling result in physiologic and phenotypic abnormalities. To date, numerous studies have highlighted BRs-induced stress tolerance to various environmental extremes such as high temperature, chilling, drought, salinity and heavy metals in a range of plant species. However, the in-depth mechanisms of BRs-induced stress tolerance still remain largely unknown. It is now clear that BRs-induced stress responses are strictly concentration de- pendent and the optimal concentration for improving the plant adaptability may vary depending on the plant species, developmental stages and environmental conditions as well. Conflicting evidences concerning regulation of stress adaptation by BRs demand further elucidation of mechanism of BRs action in response to environmental stresses in plants. Recent advances in phytohormone research suggest that the effect of BRs on stress tolerance relies largely on its interplay with other hormones. In this review, we critically analyze the multifaceted roles of BRs in various abiotic stresses and its potential crosstalk with other hormones in stress adaptation. The discrepancy in the dose and mode of application of BRs analogues for stress management is also discussed.

Tomato (Solanum lycopersicum L.) is a major agricultural crop cultivated over the world. The elaboration of new effective plant growth regulators for improving growth of tomato is an important task for plant biotechnology. In the present work the comparative effect of plant hormones auxins IAA and NAA, cytokinin Kinetin, and new synthetic compounds pyrimidine derivatives on acceleration of vegetative growth of tomato was studied. The obtained biometric indices of 24 th-day-old tomato seedlings grown on the water solution of pyrimidine derivatives used at the concentration 10-8 M were similar or higher of the biometric indices of tomato seedlings grown on the distilled water (control), or on the water solution of IAA, NAA and Kinetin used at the same concentration 10-8 M in average: at the 29-255 %, 22-235 %, 10-156 %, and 13-95 %-by total number of roots, and at the 23-255 %, 21-115 %, 19-138 %, and 9-61 %-by total length of roots, respectively. The content of photosynthetic pigments in tomato seedlings grown on the water solution of pyrimidine derivatives was increased in average: chlorophyll a-at the 17-116 %, 17-122 %, 19-22 %, and 19-52 %; chlorophyll bat the 19-155 %, 21-161 %, 12-45 %, and 11-81 %; chlorophylls a+b-at the 16-126 %, 13-132 %, 23-28 %, and 14-60 %; carotenoids-at the 15-86 %, 19-107 %, 20-31%, and 16-50 %, as compared with similar indices of tomato seedlings grown on the distilled water (control), or on the water solution of IAA, NAA and Kinetin, respectively. The content of total soluble proteins in tomato seedlings grown on the water solution of pyrimidine derivatives was increased in average: at the 40-241 %, 9-145 %, 15-122 %, and 17-123 %, as compared with similar indices of tomato seedlings grown on the distilled water (control), or on the water solution of IAA, NAA and Kinetin, respectively. The relationship between chemical structure and plant growth regulatory activity of pyrimidine derivatives was set. The highest growth regulatory activity revealed the compounds, derivatives of dihydroimidazo[1,2-c]pyrimidine. The obtained results confirmed the possibility of application of pyrimidine derivatives as new effective regulators of vegetative growth of tomato.

DELLA proteins are nuclear-localized negative regulators of gibberellin signaling found ubiquitously throughout higher plants. Dominant dwarfi ng mutations of DELLA proteins have been primarily responsible for the dramatic increases in harvest index of the 'green revolution'. Maize contains two genetic loci encoding DELLA proteins, dwarf plant8 (d8) and dwarf plant 9 (d9). The d8 gene and three of its dominant dwarfi ng alleles have been previously characterized at the molecular level. Almost 20 years after the initial description of the mutant, this investigation represents the fi rst molecular characterization of d9 and its gibberellin-insensitive mutant, D9-1. We have molecularly, subcellularly and phenotypically characterized the gene products of fi ve maize DELLA alleles in transgenic Arabidopsis. In dissecting the molecular differences in D9-1, a critical residue for normal DELLA function has been uncovered, corresponding to E600 of the D9 protein. The gibberellin-insensitive D9-1 was found to produce dwarfi ng and, notably, earlier fl owering in Arabidopsis. Conversely, overexpression of the D9-1 allele delayed fl owering in transgenic maize, while overexpression of the d9 allele led to earlier fl owering. These results corroborate fi ndings that DELLA proteins are at the crux of many plant developmental pathways and suggest differing mechanisms of fl owering time control by DELLAs in maize and Arabidopsis.

Brassinosteroids (BRs) are ubiquitous plant steroid hormones, playing diverse roles in plant growth, development and stress responses. Defects in BRs biosynthesis or signaling result in physiol- ogic and phenotypic abnormalities. To date, numerous studies have highlighted BRs-induced stress tolerance to various environmental extremes such as high temperature, chilling, drought, salinity and heavy metals in a range of plant species. However, the in-depth mechanisms of BRs-induced stress tolerance still remain largely unknown. It is now clear that BRs-induced stress responses are strictly concentration de- pendent and the optimal concentration for improving the plant adaptability may vary depending on the plant species, de- velopmental stages and environmental conditions as well. Conflicting evidences concerning regulation of stress adaptation by BRs demand further elucidation of mechanism of BRs action in response to environmental stresses in plants. Recent advances in phytohormone research suggest that the effect of BRs on stress tolerance relies largely on its interplay with other hormones. In this review, we critically analyze the multifaceted roles of BRs in various abiotic stresses and its po- tential crosstalk with other hormones in stress adaptation. The discrepancy in the dose and mode of application of BRs analogues for stress management is also discussed

Plants interact with their environment by modifying gene expression patterns. One mechanism for this interaction
involves epigenetic modifications that affect a number of aspects of plant growth and development. Thus, the
epigenome is highly dynamic in response to environmental cues and developmental changes. Flowering is
controlled by a set of genes that are affected by environmental conditions through an alteration in their expression
pattern. This ensures the production of flowers even when plants are growing under adverse conditions, and thereby
enhances transgenerational seed production. In this review recent findings on the epigenetic changes associated
with flowering in Arabidopsis thaliana grown under abiotic stress conditions such as cold, drought, and high salinity
are discussed. These epigenetic modifications include DNA methylation, histone modifications, and the production
of micro RNAs (miRNAs) that mediate epigenetic modifications. The roles played by the phytohormones abscisic
acid (ABA) and auxin in chromatin remodelling are also discussed. It is shown that there is a crucial relationship
between the epigenetic modifications associated with floral initiation and development and modifications
associated with stress tolerance. This relationship is demonstrated by the common epigenetic pathways through
which plants control both flowering and stress tolerance, and can be used to identify new epigenomic players.

Study of plant growth regulating activity of synthetic low molecular weight heterocyclic compounds derivatives of pyrimidine, pyrazole, and oxazole was conducted. It was found that all tested synthetic heterocyclic compounds used at concentration 10-9 M/l of distilled water revealed high stimulating auxin-like activity on vegetative growth of two cultivars of pea and maize, and stimulating cytokinin-like activity on growth of the isolated cotyledons of pumpkin. The obtained biometric indexes of 21 st-day-old seedlings of pea (Pisum sativum L.) of cultivar L35/11 middle stalwart bewhiskered grown on the water solution of heterocyclic compounds used at concentration 10-9 M/l of distilled water were higher of the biometric indexes of 21 st-day-old seedlings of pea grown either on the distilled water (control) or on the water solution of auxins IAA and NAA used at the same concentration 10-9 M/l of distilled water in average: at the 7-8% - by total length of seedlings, at the 6-46%-by total length of roots, and at the 15-70% - by total number of roots. The obtained biometric indexes of 21 st-day-old seedlings of pea (Pisum sativum L.) of cultivar L303/04 semi-dwarf bewhiskered grown on the water solution of heterocyclic compounds used at concentration 10-9 M/l of distilled water were higher of the biometric indexes of 21 st-day-old seedlings of pea grown either on the distilled water (control) or on the water solution of auxins IAA and NAA used at the same concentration 10-9 M/l of distilled water in average: at the 18-23% - by total length of seedlings, at the 15-76% - by total length of roots, and at the 16-116% - by total number of roots. The obtained biometric indexes of 14 th-day-old seedlings of maize (Zea mays L.) hybrid Palmyra FAO 190 grown on the water solution of heterocyclic compounds used at concentration 10-9 M/l of distilled water were higher of the biometric indexes of 21 st-day-old seedlings of maize grown either on the distilled water (control) or on the water solution of auxins IAA and NAA used at the same concentration 10-9 M/l of distilled water in average: at the 23 % - by total length of seedlings, 5-37% - by total length of roots, and at the 7-87% - by total number of roots. The specific bioassay on cytokinin-like activity conducted on the 16 th-day-old cotyledons isolated from seeds of muscat pumpkin (Cucurbita moschata Duch. et Poir.) of cultivar Gilea, showed that all heterocyclic compounds derivatives of pyrimidine, pyrazole, and oxazole used at concentration 10-9 M/l of distilled water demonstrated high stimulating cytokinin-like activity. The indexes of biomass growth of isolated cotyledons of pumpkin grown on the water solution of heterocyclic compounds used at concentration 10-9 M/l of distilled water were higher of the indexes of biomass growth of isolated cotyledons of pumpkin grown either on the distilled water (control) or on the water solution of phytohormone cytokinin Kinetin used at the same concentration 10-9 M/l of distilled water in average at the 6-30%. It was shown also the positive effect of some from tested synthetic heterocyclic compounds derivatives of pyrimidine, pyrazole, and oxazole on activation of photosynthetic processes in the leaves of 21 st-day-old pea seedlings and 14 th-day-old maize seedlings due to increase of synthesis of photosynthetic pigments in the plant cells; the content of chlorophyll a was increased in average at the 4-36%; the content of chlorophyll b was increased in average at the 3-74%; the content of chlorophylls a+b was increased in average at the 5-36%; the chlorophylls a/b ratio was increased in average at the 3-44%; the content of carotenoids was increased in average at the 3-37% as compared with control, IAA and NAA, respectively; the carotenoid/chlorophyll ratio was increased in average at the 7-17% as compared with control. The application in agricultural biotechnology of synthetic low molecular weight heterocyclic compounds derivatives of pyrimidine, pyrazole, and oxazole as new effective substitutes of phytohormones auxins and cytokinins for improving of cultivation of pea, maize, and pumpkinis is proposed.

The phytohormone-like activity of synthetic low molecular weight heterocyclic compounds derivatives of pyrimidine, pyridine, pyrazole, and isoflavones was studied. Testing of stimulating effect of synthetic heterocyclic compounds on seed germination and seedling growth of flax (Linum usitatissimum L.) of cultivar Ukrainian 3 showed expressive auxin-like activity of these compounds. The growth parameters of 15 th-day-old flax seedlings grown on the solution of heterocyclic compounds used at concentration 10-8 M/l of distilled water were higher or similar to growth parameters of flax seedlings grown on the water solution of auxins IAA and NAA used at the same concentration as compared to lower growth parameters of control flax seedlings grown on the distilled water (control). The specific bioassay on auxin-like activity showed high stimulating effect of heterocyclic compounds derivatives of pyrimidine, pyridine, pyrazole, and isoflavones used at concentration 10-8 M/l of distilled water on rhizogenesis on the 14 th-day-old leaf petioles isolated from seedlings of haricot bean (Phaseolus vulgaris L.) of cultivar Belozernaya. The specific bioassay on cytokinin-like activity conducted on the 16 th-day-old cotyledons isolated from seeds of muscat pumpkin (Cucurbita moschata Duch. et Poir.) of cultivar Gilea, showed that heterocyclic compounds derivatives of pyrimidine, pyridine, pyrazole, and isoflavones used in concentration 10-8 M/l of distilled water demonstrated high stimulating activity on growth of biomass of isolated cotyledons of pumpkin, which was similar or higher than activity of cytokinin Kinetin. The specific bioassay on gibberellin-like activity conducted on the 3 rd-day-old seedlings of lettuce (Lactuca sativa L.) of cultivar Berlin testified that some heterocyclic compounds derivatives of pyrazole, isoflavones, and pyridine used in concentrations ranging from 10-4 M to 10-9 M/1 of distilled water revealed minor stimulating effect on elongation of hypocotyl of lettuce seedlings in relation to control, but their activity was significantly lower than activity of gibberellic acid GA3. This bioassay showed also that the some heterocyclic compounds derivatives of pyrazole and isoflavones used in concentration 10-7 M/l of distilled water demonstrated nonspecific for this bioassay auxin-like activity, which manifested in stimulation of formation and growth of root system on the seedlings of lettuce. Obtained results confirmed specific auxin-like and cytokinin-like, and minor gibberellin-like effect of synthetic heterocyclic compounds on cell division, cell proliferation, cell elongation and cell differentiation that are the basic processes of plant growth and development.

Current study was designed to explore the antiemetic effect of the methanolic extract of Tithonia diversifolia (Hemsl.) A. Gray., leaves using chick emesis model in order to validate their folk use in G.I. disorders. Emesis was induced by the oral administration of copper sulfate 50mg/kg body weight to male chicks of four days age. The antiemetic activity was determined by calculating the mean decrease in number of retching in contrast with those of control. Tithonia diversifolia leaves extract (150 mg/kg orally) showed significant (p < 0.05) antiemetic effect and compared with reference drug chlorpromazine.

In the natural world, plants have to withstand and counteract stress havoc like biotic and abiotic stressors throughout their life cycle. To survive and perform vital biological processes, plants have evolved a variety of complex ways to detect environmental cues and respond appropriately. Phytohormones such as abscisic acid, salicylic acid, jasmonic acid, and ethylene, regulate plant defenses through synergistic and antagonistic actions. Cross-talk among these hormones enables the plant to utilize less energy for defense response and allocate it for growth and development. Crosstalk helps in prioritizing and optimizing the response according to the severity of specific stress. With the elucidation of important gene structure and functions through omics approaches and their experimental validation, functional mutant studies have revealed several unique and shared mechanisms involved in cross-talk between different signaling networks. In this review, we discuss how plant hormones coordinate with various signaling components such as transcription factors, signaling proteins, mitogen-activated protein kinase, and reactive oxygen species to orchestrate a fine balance of the primary and secondary stress responses during biotic and abiotic stress. Further, the emerging roles of novel molecules such as indoleamine serotonin, melatonin, methylglyoxal, spermine, etc. as moderators of cross-talk have been discussed. The final section of this article deals with the regulation of phytohormone networks by small RNAs and epigenetic regulations.

The elaboration of new effective and ecologically friendly regulators improving growth and increasing yield of oilseed rape is an actual problem for modern agriculture. Our work was devoted to screening of new effective plant growth regulators among chemical low molecular weight heterocyclic compounds, derivatives of oxazole and oxazolopyrimidine to improve the germination of seeds and growth of seedlings of oilseed rape (Brassica napus L.) of cultivar Kalinivsky. As a result of the conducted experiments, the most effective synthetic compounds that showed a high stimulating effect when used in concentration 10-9 M on the growth of 21 st-day-old oilseed rape seedlings were selected. It was found that biometric indices of 21 st-day-old oilseed rape seedlings grown on the 10-9 M solution of derivatives of oxazole and oxazolopyrimidine were increased by an average to 11-30 % – by length of shoots, by an average to 8-68 % – by total number of roots, and by an average to 5-43 % – by total length of roots, as compared with similar indices of 21 st-day-old oilseed rape seedlings grown on the distilled water (control) or on the 10-9 M solution of plant hormones auxins IAA (1H-Indol-3-ylacetic acid) and NAA (1-Naphthylacetic acid). The content of photosynthetic pigments in the leaves of 21 st-day-old oilseed rape seedlings grown on the 10-9 M solution of derivatives of oxazole and oxazolopyrimidine was increased by an average to 14-20 % – by content of chlorophyll a, by an average to 15-21 % – by content of chlorophyll b, by an average to 16 – 18 % – by content of chlorophyll a+b, as compared with similar indices of 21 st-day-old oilseed rape seedlings grown on the distilled water (control) and were increased by an average to 14-26 % – by content of carotenoids as compared with similar indices of 21 st-day-old oilseed rape seedlings grown on the distilled water (control) or grown on the 10-9 M solution of IAA and NAA, respectively. The obtained results confirmed the possibility of using of derivatives of oxazole and oxazolopyrimidine as new effective regulators to improve oilseed rape growth.
Keywords: oilseed rape, growth regulators, oxazole and oxazolopyrimidine, auxins
IAA and NAA.

This is a short review of the classical and new, natural and synthetic plant hormones and growth regulators (phytohormones) and highlights some of their uses in plant tissue culture. Plant hormones rarely act alone, and for most processes-at least those that are observed at the organ level--many of these regulators have interacted in order to produce the final effect. The following substances are discussed: (a) Classical plant hormones (auxins, cytokinins, gibberellins, abscisic acid, ethylene) and growth regulatory substances with similar biological effects. New, naturally occurring substances in these categories are still being discovered. At the same time, novel structurally related compounds are constantly being synthesized. There are also many new but chemically unrelated compounds with similar hormone-like activity being produced. A better knowledge of the uptake, transport, metabolism, and mode of action of phytohormones and the appearance of chemicals that inhibit synthesis, transport, and action of the native plant hormones has increased our knowledge of the role of these hormones in growth and development. (b) More recently discovered natural growth substances that have phytohormonal-like regulatory roles (polyamines, oligosaccharins, salicylates, jasmonates, sterols, brassinosteroids, dehydrodiconiferyl alcohol glucosides, turgorins, systemin, unrelated natural stimulators and inhibitors), as well as myoinositol. Many of these growth active substances have not yet been examined in relation to growth and organized development in vitro.

Plant growth regulator (PGR) crosstalk and interaction with the plant’s genotype and environmental factors play a crucial role in microspore embryogenesis (ME), controlling microspore-derived embryo differentiation and development as well as haploid/doubled haploid plant regeneration. The complexity of the PGR network which could exist at the level of biosynthesis, distribution, gene expression or signaling pathways, renders the creation of an integrated model of ME-control crosstalk impossible at present. However, the analysis of the published data together with the results received recently with the use of modern analytical techniques brings new insights into hormonal regulation of this process. This review presents a short historical overview of the most important milestones in the recognition of hormonal requirements for effective ME in the most important crop plant species and complements it with new concepts that evolved over the last decade of ME studies.

Brassinosteroids (BRs) act as immune-modulators for generating plant growth and development. It regulated either activation or suppression of various key enzymatic reactions, activation of synthesis of protein, and generation of various defense modulating compounds for the plant kingdom. BRs play a vital role in regulating cellular differentiation, pollen development, fruit ripening, and quality seed formation. BRs regulates the various physiological process including root growth during nutrient deficiency such as nitrogen, phosphorus, boron and tends to signal the nutrient distribution in the rhizosphere level for better growth and high yield in crop plants. This review highlighted the role of BRs in plant growth and development and stress response, understanding the BR pathway, the molecular mechanism of BR signaling in various tissues, crosstalk between BRs and other phytohormones, gene involves in the brassinosteroids signaling pathway, biosynthesis and role of BRs in biomass production and crop yield. Review Article Praveena et al.; CJAST, 39(25): 174-196, 2020; Article no.CJAST.59978 175

The elaboration of new plant growth regulators (PGRs) as effective substituents of plant hormones to improve the growth and increase the yield of vegetable crops is an important task for successful development of modern agriculture. Cucumber (Cucumis sativus L.) belongs to important food and medicinal plants cultivated in different countries of the world. Our work was aimed to study of regulatory effect of synthetic low molecular weight heterocyclic compounds (LMWHC), derivatives of [1,3]oxazolo[5,4-d]pyrimidine and N-sulfonyl substituted of 1,3-oxazole on vegetative growth of cucumber plants (Cucumis sativus L.) of cultivar Dzherelo. The obtained results showed that some from tested LMWHC used at concentration 10-9 M revealed high auxin-like and cytokinin-like stimulating effect on germination of seeds and acceleration of growth of cucumber seedlings grown for 24 days in the laboratory conditions. The relationship between chemical structure and plant growth regulatory activity of synthetic LMWHC was observed. The practical application of synthetic LMWHC derivatives of [1,3]oxazolo[5,4-d]pyrimidine and N-sulfonyl substituted of 1,3-oxazole as new effective regulators of growth of cucumber plants was proposed.

The review is devoted to genetic mechanisms of regulation of plant embryonic development. Numerous families of genes
identified to date that control this phase of plant ontogenesis are presented in detail; their key role in the formation and
development of plant seed is described. Data concerning important role of different classes of phytohormones such as
auxins, cytokinins, gibberellic acid, brassinosteroids, abscisic acid, ethylene and jasmonic acid in the regulation of plant
growth and development during embryogenesis are resulted.
Keywords: Plant Seed; Plant Embryonic Genes; Differentiation and Specialization of Embryonic Cells; Seed Growth and
Development; Plant Hormones; Auxins; Cytokinins; Gibberellic Acid; Brassinosteroids; Abscisic Acid; Ethylene; Jasmonic
Acid; Developmental and Phytohormonal Regulation of Plant Embryonic Genes.

The temperature across the globe is constantly changing for the worse of the biotic beings viz., the flora and fauna. Rapid temperature changes are the result of continuous interference of human beings as a bane post the rapid industrialization and urbanization. The ever increasing and decreasing ranges of temperature in the environment are leading to the malfunctioning of various physiological and biochemical processes in plants thereby resulting in severe temperature stresses in terms of high temperature/ heat stress as well as low temperature stress (chilling and freezing stress). Brassinosteroids (BRs) are a novel group of plant growth regulators (PGR's) with significant growth promoting activity. BRs were initially extensively studied for their profound growth promoting physiological responses viz., growth and yield, seed germination, photosynthesis, senescence, photomorphogenesis, flowering etc. BRs have been further explored for stress-protective properties in plants against a number of abiotic stresses like heat, chilling, freezing, drought, flooding, oxidative, salt, allelochemicals, radiation, light, wind, heavy metals stresses etc,. and can be aptly stated that BRs induce plant tolerance to a wide spectrum of stresses. The present review is a study on the role of BRs in mitigating the effect of temperature stress in plants viz., high temperature/heat stress as well as low temperature stress (chilling and freezing stress).

Plants are exposed to a variety of abiotic stresses in nature and exhibit unique and complex responses to these stresses depending on their degree of plasticity involving many morphological, cellular, anatomical, and physiological changes. Phytohormones are known to play vital roles in the ability of plants to acclimatize to varying environments, by mediating growth, development, source/sink transitions and nutrient allocation. These signal molecules are produced within the plant, and also referred as plant growth regulators. Although plant response to salinity depends on several factors; nevertheless, phytohormones are thought to be the most important endogenous substances that are critical in modulating physiological responses that eventually lead to adaptation to salinity. Response usually involves fluctuations in the levels of several phytohormones, which relates with perceives salinity and trigger the signal transduction cascades via phytohormones is vital to devise salinity related breeding and transgenic approaches.

In our work the low molecular weight heterocyclic compounds derivatives of [1,3]oxazolo[5,4-d]pyrimidine and N-sulfonyl substituted of 1,3-oxazole were synthesized. Comparative analysis of plant growth stimulating activity of these heterocyclic compounds and plant hormones auxins IAA and NAA, and cytokinin Kinetin was conducted. It was found that all tested heterocyclic compounds used in concentration 10-9 M/l of distilled water revealed high auxin-like growth stimulating activity on the soybean (Glycine max L.) of cultivar Valuta, wheat (Triticum aestivum L.) of cultivar Zimoyarka, and flax (Linum usitatissimum L.) of cultivar Svitanok. The growth parameters of 20 th-day-old seedlings of soybean, wheat, and flax grown on the 10-9 M water solutions of heterocyclic compounds were as generally similar or higher than the growth parameters of seedlings grown on the water solution of auxins IAA and NAA used in the same concentration as compared to lower growth parameters of control untreated seedlings grown on the distilled water. Specific bioassay on cytokinin-like activity, conducted on the isolated cotyledons of muscat pumpkin (Cucurbita moschata Duch. et Poir.) of cultivar Gilea, showed that all testing heterocyclic compounds used in concentration 10-9 M/l of distilled water demonstrated expressive cytokinin-like stimulating effect on the growth of the isolated cotyledons of pumpkin. Obtained data confirm perceptiveness of application derivatives of [1,3]oxazolo[5,4-d]pyrimidine and N-sulfonyl substituted of 1,3-oxazole in the agricultural practice for intensification of growth and development of soybean, wheat, flax and pumpkin plants.

Keywords: [1,3]oxazolo[5,4-d]pyrimidine and N-sulfonyl substituted of 1,3-oxazole, IAA, NAA, Kinetin, Glycine max L., Triticum aestivum L., Linum usitatissimum L., Cucurbita moschata Duch. et Poir

This is a short review of the classical and new, natural and synthetic plant hormones and growth regulators (phytohormones) and highlights some of their uses in plant tissue culture. Plant hormones rarely act alone, and for most processes-at least those that are observed at the organ level--many of these regulators have interacted in order to produce the final effect. The following substances are discussed: (a) Classical plant hormones (auxins, cytokinins, gibberellins, abscisic acid, ethylene) and growth regulatory substances with similar biological effects. New, naturally occurring substances in these categories are still being discovered. At the same time, novel structurally related compounds are constantly being synthesized. There are also many new but chemically unrelated compounds with similar hormone-like activity being produced. A better knowledge of the uptake, transport, metabolism, and mode of action of phytohormones and the appearance of chemicals that inhibit synthesis, transport, and action of the native plant hormones has increased our knowledge of the role of these hormones in growth and development. (b) More recently discovered natural growth substances that have phytohormonal-like regulatory roles (polyamines, oligosaccharins, salicylates, jasmonates, sterols, brassinosteroids, dehydrodiconiferyl alcohol glucosides, turgorins, systemin, unrelated natural stimulators and inhibitors), as well as myoinositol. Many of these growth active substances have not yet been examined in relation to growth and organized development in vitro.

Streszczenie: Rodnik hydroksylowy (OH•) posiadający niesparowany elektron i charakteryzujący się bardzo krótkim okresem półtrwania (10-9 s) jest najbardziej reaktywną formą tlenu (ang. Reactive Oxygen Species, ROS), zdolną do wchodzenia w reakcje ze wszystkimi substancjami
w komórce. Do niedawna uznawany był głównie za produkt uboczny metabolizmu tlenowego, wykazujący niezwykle szkodliwy wpływ na życie organizmów. Jednakże, coraz więcej nowych dowodów potwierdza istotną, pozytywną rolę OH• w prawidłowym funkcjonowaniu komórek roślinnych.
Jego silne właściwości utleniające mają istotne znaczenie w regulacji kiełkowania, wzrostu, otwierania i zamykania aparatów szparkowych, reprodukcji, indukowania reakcji odporności, czy też aklimatyzacji do warunków stresowych. W apoplaście i we wnętrzu komórek OH• jest produkowany
przez szereg peroksydaz, dysmutaz ponadtlenkowych i oksydaz NADPH, jak również może powstawać na drodze nieenzymatycznej. Poziom komórkowego OH• i jego działanie muszą być ściśle kontrolowane, zarówno w celu uniknięcia uszkodzeń komórek, jak i ze względu na zdolność dyfuzji tego rodnika. Niniejszy artykuł przedstawia najnowsze odkrycia dotyczące powstawania i mechanizmów działania OH• oraz szereg dowodów na to, że cząsteczka ta jest ważnym regulatorem wzrostu i rozwoju roślin.
Słowa kluczowe: kiełkowanie, reaktywne formy tlenu, rodnik hydroksylowy, stresy biotyczne i abiotyczne,
transdukcja sygnału, wzrost elongacyjny

In the recent years in many countries around the world, the "in vitro" cultivation method has a wide use in studying and producing many agricultural crops, ornamental and forest plants. The solution of various problems that arise during the "in vitro" cultivation of plants as is the defining of the medium feeder, citokinins and auxines impact, selection of meristems and the optimum growth conditions, are the foundations of biotechnology today. The purpose of this study is determining of the optimal concentration of citokinins for shoot proliferation. For experimenting were taken from plum plants, cv "shengjine" and as a starting material for performing experiments are used meristems tissue during vegetative period and early branches of the plum during winter. Development of shoots in the specified medium along with other modifications requires that in the field to be added the citokinin -BAP (benzylaminopurine). M-S medium with the ½ of macro & micronutrients was proved with different doses of BAP 0.5, 1, 1.5, 2 mg / l. In the same growth conditions. For the best dose of this phytohormone was judged based on the number of shoots and their length.

Endophytic bacteria colonize plants and live inside them for part of or throughout their life without causing any harm or disease to their hosts. The symbiotic relationship improves the physiology, fitness, and metabolite profile of the plants, while the plants provide food and shelter for the bacteria. The bacteria-induced alterations of the plants offer many possibilities for biotechnological, medicinal, and agricultural applications. The endophytes promote plant growth and fitness through the production of phytohormones or biofertilizers, or by alleviating abiotic and biotic stress tolerance. Strengthening of the plant immune system and suppression of disease are associated with the production of novel antibiotics, secondary metabolites, siderophores, and fertilizers such as nitrogenous or other industrially interesting chemical compounds. Endophytic bacteria can be used for phytoremediation of environmental pollutants or the control of fungal diseases by the production of lytic ...

The of auxin-like and cytokinin-like activities of new chemical low molecular weight heterocyclic compounds, derivatives of pyrimidine, pyrazole, isoflavones, pyridine, oxazolopyrimidine and oxazole were studied. The specific bioassay on auxin-like activity showed high stimulating effect of the chemical heterocyclic compounds, derivatives of pyrimidine, pyrazole, isoflavones, and pyridine used at the concentration 10-8 M on the formation of adventitious roots on the 14 th-day-old leaf petioles isolated from seedlings of haricot bean (Phaseolus vulgaris L.) cultivar Belozernaya, which was similar or higher of the effect of plant hormones auxins IAA and NAA used at the same concentration 10-8 M. The specific bioassay on cytokinin-like activity showed the high stimulating effect of the chemical heterocyclic compounds, derivatives of pyrimidine, pyrazole, isoflavones, pyridine, oxazolopyrimidine and oxazole used at the concentrations 10-8 M and 10-9 M on the growth of biomass of 16 th-day-old cotyledons isolated from seeds of muscat pumpkin (Cucurbita moschata Duch. et Poir.) cultivar Gilea, which was similar or higher of the effect of plant hormone cytokinin Kinetin used at the same concentrations 10-8 M and 10-9 M. The obtained results proved the inducing auxin-like and cytokinin-like effect of synthetic heterocyclic compounds on plant cell elongation, division, and differentiation that are the basic processes of plant growth.

Plants are exposed to a variety of abiotic stresses in nature and exhibit unique and complex responses to these stresses depending on their degree of plasticity involving many morphological, cellular, anatomical, and physiological changes. Phytohormones are known to play vital roles in the ability of plants to acclimatize to varying environments, by mediating growth, development, source/sink transitions and nutrient allocation. These signal molecules are produced within the plant, and also referred as plant growth regulators. Although plant response to salinity depends on several factors; nevertheless, phytohormones are thought to be the most important endogenous substances that are critical in modulating physiological responses that eventually lead to adaptation to salinity. Response usually involves fluctuations in the levels of several phytohormones, which relates with perceives salinity and trigger the signal transduction cascades via phytohormones is vital to devise salinity related breeding and transgenic approaches.