Letteratura scientifica selezionata sul tema "Plant growth inhibiting substances"

Thirteen of the new synthetized 2-R substituted benzothiazole derivatives have been tested for plant growth regulatory (PGR) activity. The effect on growth elongation was studied on wheat coleoptile segments Triticum aestivum L. cv. Blava, and on the hypocotyl and roots in cucumber Cucumis sativum L. cv. Evita. The formation and number of adventitious roots and the length of hypocotyl in Vigna radiata (L.) Wilczek and, the effect on the length of stem, fresh and dry mass in buckwheat Fagopyrum esculentum Moench. cv. Pyra were evaluated. Cytokinin activity was determined on segments of barley leaves Hordeum vulgare L. cv. Jubilant on the basis of senescence inhibition and chlorophyll content. The benzothiazole derivatives were tested in the range of 10^–3–10^–7M concentrations, and PGR activity was compared with indole-3-acetic acid, indole-3-butyric acid and 6-furfurylaminopurine. All tested derivatives showed different auxine-like effects on elongation growth of plants and the stimulative effects were found to depend on applicable concentrations. At higher concentration rates, derivatives acted as growth retardants and inhibited the length of cucumber hypocotyl and roots. The derivatives increased the formation of adventitious roots of mung bean hypocotyl cuttings, as well as stem elongation and production of fresh and dry mass of buckwheat. Cytokinin activity was confirmed in one derivate only with a significant effect on the inhibition of leaf senescence and higher chlorophyll content. The tested benzothiazole derivatives may be characterized as biologically active substances with dominant auxine-like growth promoting activity

Velvetleaf (Abutilon theophrastiMedik. # ABUTH) seeds were bioassayed on 241 microbial isolates to assess their antimicrobial activity. Seeds placed on agar plates inoculated with test microorganisms released a diffusible substance(s) that inhibited the growth of 117 of 202 (58%) bacteria and all of the fungi tested. Antimicrobial activity of the seeds appeared to be nonselective as the extent of inhibition was not related to type of microorganism nor their origin. Hard, water-impermeable seeds had greater inhibitory activity than imbibed (soft) seeds. The intensity of inhibition was affected by prior leaching of seeds with various solvents and by the stage of seed development. Chemical analysis of diffusion zones from agar plates and seed leachates revealed the presence of phenolic compounds. The presence of antimicrobial substances in velvetleaf seeds may contribute to the persistence of viable seeds in soil by inhibiting potential seed-deteriorating microorganisms.

Investigation of plants that possess natural antimicrobial substances for plant protection has been recognized as a promising disease management strategy. Alternaria alternata, Fusarium solani, Macrophomina spp., and Pestalotiopsis spp. isolated from diverse hosts such as Azadirachta indica, Melia dubia, Saraca indica and Quercus leucotrichophora produce important diseases in forest nurseries such as leaf blight, leaf spot, and wilt. In this study, botanicals from two invasive plant species, Ageratina adenophora and Ageratum conyzoides, were prepared and tested against plant diseases. Two botanicals (Methanolic extract obtained from the leaves of these two invasive species) and two fungicides were evaluated for their fungal growth inhibitory effects. At 1.5 percent concentration, the methanolic extract of Ageratina adenophora was found highly effective, inhibiting the growth of Macrophomina spp., (71.94%) followed by Pestalotiopsis spp. (70.20%), Alternaria alternate (51.92%) and Fusarium solani (47.03%). Whereas, Systemic chemical fungicide Thiophanate methylat 1.5% concentration showed maximum mycelial growth inhibition of Alternaria alternata (77.20%) and Macrophomina spp. (82.43%) and being deadlier to Pestalotiopsis spp. (100%) and Fusarium solani (100%). Their comparative analysis showed that higher doses of Ageratina adenophora caused either more or almost equal pathogen growth inhibition than lower doses of Chlorothalonil for certain fungi. Thus, promoting eco-friendly disease management strategies such as botanical control would be beneficial in reducing the need for pesticides.

Introduction: Caries are initiated by the plaque formation on the tooth surface, due to the interaction between food debris and bacteria in the mouth. The pioneer bacterium of plaque formation is Streptococcus sanguis. The Strawberry fruit, lime fruit, and radish root are part of the plant that contains antibacterial substances. Flavonoid, tannin, saponin, alkaloid, polyphenol, terpenoid and quinon as antibacterial substances. This study aimed to evaluate strawberry fruit, lime fruit, and radish root methanol extract can inhibit Streptococcus sanguis ATCC 10556. Therefore, strawberry, lime, and radish can be made into mouthwash, bubble gum, or toothpaste to prevent plaque formation. Methods: This study used a Kirby-Bauer diffusion test as the inhibition test. Results: The result of this study that the biggest inhibition zone was lime methanol extract 20,000 ppm, and the smallest one was radish methanol extract 5,000 ppm. Conclusion: Strawberry fruit, lime fruit peel, and radish root methanol extract and their combination had the effect of inhibiting bacterial growth synergistically against Streptococcus sanguis ATCC 10556.

Soybean Fusarium wilt and root rot disease caused by a necrotrophic ascomycete pathogen, F. oxysporum, triggered severe damage to the plant tissues and organs and impacted heavy losses. Biocontrol agents, Bacillus subtilis, were commonly used to produce a broad spectrum of antifungal substances and were gradually used in biocontrol studies for plant disease management. Investigation and determination of the inhibiting mechanism of antifungal substance produced by B. subtilis on F. oxysporum should be done to protect the soybean plant. This study revealed that basal nutrient broth (NB) gives the best antifungal activity. The stationary phase of the bacterial growth curve was obtained on two days of cultivation and showed the maximum antifungal activity against F. oxysporum. Ethyl acetate (EA) extraction of bacterial supernatant generated crude EA extract, which showed half inhibition (IC50) at 306.42 µg/ml obtained from the dose-response regression curve. Post-treatment mycelia of F. oxysporum with bacterial extract were demonstrated as hyphal deformation followed by malondialdehyde (MDA) accumulation. Furthermore, cellular leakage on fungal cells that may be triggered by antifungal compounds from strain W3.15 occurred. Last, the related antifungal compounds were predicted to be epicatechin and benzophenone from the LC-MS/MS analysis of crude EA extract. Accordingly, the biocontrol agent B. subtilis strain W3.15 promises a strong potency for biofungicide development.

Plant pathogens pose major threats on agriculture and horticulture, causing significant economic loss worldwide. Due to the continuous and excessive use of synthetic pesticides, emergence of pesticide resistant pathogens has become more frequent. Thus, there is a growing needs for environmentally-friendly and selective antimicrobial agents with a novel mode of action, which may be used in combination with conventional pesticides to delay development of pesticide resistance. In this study, we evaluated the potentials of lichen substances as novel biopesticides against eight bacterial and twelve fungal plant pathogens that have historically caused significant phytopathological problems in South Korea. Eight lichen substances of diverse chemical origins were extracted from axenic culture or dried specimen, and further purified for comparative analysis of their antimicrobial properties. Usnic acid and vulpinic acid exhibited strong antibacterial activities against Clavibacter michiganensis subsp. michiganensis. In addition, usnic acid and vulpinic acid were highly effective in the growth inhibition of fungal pathogens, such as Diaporthe eres, D. actinidiae, and Sclerotinia sclerotiorum. Intriguingly, the growth of Rhizoctonia solani was specifically inhibited by lecanoric acid, indicating that lichen substances exhibit some degrees of selectivity to plant pathogens. These results suggested that lichen substance can be used as a selective biopesticide for controlling plant disease of agricultural and horticultural significance, minimizing possible emergence of pesticide resistant pathogens in fields.

Bacteria produce antimicrobial compounds to compete for nutrients and space in a particular habitat. Antagonistic interactions can be evaluated by several methodologies including the double-layer agar and simultaneous inhibition assays. Among the well-known inhibitory substances produced by bacteria are the broad-spectrum antibiotics, organic acids, siderophores, antifungal, and bacteriocins. The most studied bacterial genera able to produce these inhibitory substances are Enterococcus, Lactococcus, Streptomyces, Bacillus, Pseudomonas, Klebsiella, Escherichia, and Burkholderia. Some beneficial bacteria can promote plant growth and degrade toxic compounds in the environment representing an attractive solution to diverse issues in agriculture and soil pollution, particularly in fields with damaged soils where pesticides and fertilizers have been indiscriminately used. Beneficial bacteria may increase plant health by inhibiting pathogenic microorganisms; some examples include Gluconacetobacter diazotrophicus, Azospirullum brasilense, Pseudomonas fluorescens, Pseudomonas protegens, and Burkholderia tropica. However, most studies showing the antagonistic potential of these bacteria have been performed in vitro, and just a few of them have been evaluated in association with plants. Several inhibitory substances involved in pathogen antagonism have not been elucidated yet; in fact, we know only 1 % of the bacterial diversity in a natural environment leading us to assume that many other inhibitory substances remain unexplored. In this review, we will describe the characteristics of some antimicrobial compounds produced by beneficial bacteria, the principal methodologies performed to evaluate their production, modes of action, and their importance for biotechnological purposes.

Hyptis suaveolens(Lamiaceae) is an exotic invasive plant in many countries. Earlier studies reported that the aqueous, methanol, and aqueous methanol extract ofH. suaveolensand its residues have phytotoxic properties. However, to date, the phytotoxic substances of this plant have not been reported. Therefore, the objectives of this study were isolation and identification of phytotoxic substances ofH. suaveolens. Aqueous methanol extract of this plant was purified by several chromatographic runs through bioassay guided fractionation using garden cress (Lepidium sativum) as a test plant. Final purification of a phytotoxic substance was achieved by reverse phase HPLC and characterized as 14α-hydroxy-13β-abiet-8-en-18-oic acid (suaveolic acid) by high-resolution ESI-MS,1H-,13C-NMR, CD, and specific rotation. Suaveolic acid inhibited the shoot growth of garden cress, lettuce (Lactuca sativa), Italian ryegrass (Lolium multiflorum), and barnyard grass (Echinochloa crus-galli) at concentrations greater than 30 µM. Root growth of all but lettuce was also inhibited at concentrations greater than 30 µM. The inhibitory activities were concentration dependent. Concentrations required for 50% growth inhibition of suaveolic acid for those test plant species were ranged from 76 to 1155 µM. Therefore, suaveolic acid is phytotoxic and may be responsible for the phytotoxicity ofH. suaveolensplant extracts.

Abstract Plant Growth Promoting Rhizobacteria (PGPR) influence plant growth by a number of direct (producing plant growth promoting substances) and indirect (through prevention of deleterious effects of phytopathogenic microorganisms) mechanisms. Five species of bacteria were isolated from rhizospheric soils of soybean and peanut fields from several locations in North Sumatra. On the basis of morphological and biochemical characteristics, the bacteria were identified as Aeromonas hydrophila, Burkholderia cepacia, Serratia ficaria, Pantoea spp. 2, and Vibrio alginolyticus. These species were tested in vitro against the causal pathogen of collar rot disease of soybean, Athelia rolfsii, which is an important soybean disease in Indonesia. The five species of bacteria were subjected to screening of antagonistic activities against A. rolfsii in vitro with a dual culture-technique. Of the five species, B. cepacia, S. ficaria and V. alginolyticus were the most effective antagonistic bacteria to control A. rolfsii. B. cepacia, S. ficaria and V. algynolitycus produced inhibiting zones against A. rolfsii of 98.35%, 97.83% and 96.97% respectively. All bacterial species showed their antagonistic activity significantly with the inhibiting zone percentage being more than 60%. The experimental results suggested that all bacterial species have a future potency as a biocontrol agent to reduce A. rolfsii collar rot disease of soybean

Inhibition of stipe growth by a substance or substances produced in the cap of Coprinus congregatus fruit bodies cultivated in continuous light has been confirmed. Caps in which maturation was induced or prevented were transferred to decapitated stipes from normally growing sporophores. Stipes were most sensitive to inhibition when treated 16–18 h before maturity. Caps from continuous-light primordia only a few hours older than the photoinhibited stage were most inhibitory. When normal primordium maturation was induced by darkness followed by light, the inhibitor disappeared from the caps 18–20 h before maturity.

Thesis (Ph. D.)--Illinois State University, 1986.
Title from title page screen, viewed July 13, 2005. Dissertation Committee: David P. Brunner (chair), Herman E. Brockman, Arlan G. Richardson, H. Tak Cheung, Lynne Lucher. Includes bibliographical references (leaves 167-183) and abstract. Also available in print.

Thesis (M.S. in Management)--Naval Postgraduate School, June 1990.
Thesis Advisor(s): Carrick, Pual M. "June 1990." Description based on signature page. DTIC Identifier(s): Plant growth regulators, growth indicators. Author(s) subject terms: Plant growth regulators, growth indicators. Includes bibliographical references (p. 39-40). Also available online.

Plant growth inhibitors were isolated from Haplopappus acradenius (Green) Blake and Baccharis sarothroides Gray, two desert species, found at the Boyce Thompson Southwestern Arboretum. Leaf and stem tissues of B. sarothroides were extracted with 80% methanol (v/v). This extract was reduced to an aqueous phase in vacuo and partitioned with ethyl acetate at pH 7.3 (NF, neutral fraction), pH 2.8 (AF, acidic fraction), and again at pH 2.8 following hydrolysis at pH 11 (HF, hydrolyzed fraction). Thin layer chromatography (TLC) on silica gel H in chloroform:ethyl acetate:formic acid (CHCl₃:EtOAc:HCOOH) produced a region between R(f)'s 0.5 to 0.6 from AF of B. sarothroides which inhibited wheat seed coleoptile and radicle growth 52.7% and 66.5%, respectively, using 500 ul of a 1.9 mg/ul extract. This section inhibited wheat coleoptile straight growth 38.6% at the same concentration. Additional TLC, UV spectrophotometry, spray reagents, NMR, and GC/MS indicated that the compound was 3,8-dihydroxy-5,6,7-trimethoxy-2-(4-methoxyphenyl)-4H-1-benzopyran-4-one at a concentration of 265 ug/g fresh weight. This compound significantly inhibited the wheat coleoptile straight growth bioassay 18.4% using 2 to 3 ug/ul. An 80% methanol extract of H. acradenius leaves evaporated in vacuo produced an aqueous insoluble brown resin. This resin dissolved in absolute methanol and separated by TLC in CHCl₃:EtOAc:HCOOH contained a region between R(f)'s 0.6 to 0.7 that inhibited wheat seed coleoptile growth 71.8% and radicle growth 90.7% using 200 ul of 1.5 mg/ul solution. Wheat coleoptile straight growth was inhibited 53.7% in this region at the same concentration. Further examination of this region by the same methods as those used for B. sarothroides indicated the presence of a C-12 alkenyl alcohol (2 mg/ml), an aromatic heterocyclic hydrocarbon (4 mg/ml), and an alkyl substituted version of 7-hydroxycoumarin (5 mg/ml) at a concentration of 0.7, 1.4, and 1.8 ug/g fresh weight, respectively. A combination of these compounds inhibited the wheat coleoptile straight growth bioassay 41.1% using 11 ug/ul. A 2 M HCl extract of H. acradenius was partitioned with diethyl ether, which was evaporated and the residue resuspended in 95% methanol. TLC in CHCl₃:EtOAc:HCOOH separated an area between R(f)'s 0.5 to 0.6 where wheat seed coleoptile growth was inhibited 49.7% and radicle growth was inhibited 54.6% using 1000 ul of a 3.3 mg/ul solution. Identified in this region was 7-hydroxycoumarin at a concentration of 150 ug/g fresh weight. The wheat coleoptile straight growth bioassy was inhibited 13.2% using 2 to 3 ug/ul.

Petrol and ethanolic extracts of six asteraceous weeds were added to artificial diet and screened for inhibition of larval growth on variegated cutworm, Peridroma saucia (Hbn.). Petrol and ethanolic extracts of Artemisia tridentata and Chamomilla suaveolens and ethanolic extracts of Chrysothamnus nauseosus and Centaurea diffusa were highly inhibitory at five times the naturally occurring concentrations. The two C. suaveolens extracts and the ethanol extract of A. tridentata were active at the natural concentration (100%) and were further examined at 20, 40, 60, and 80% of this level. Inhibition of larval growth was directly related to concentration for each of the three extracts tested. EC₅₀'S (effective concentration to inhibit growth by 50% relative to controls) for the three extracts were 36-42% of the naturally occurring level in the plants. Nutritional indices were calculated for second instar P. saucia feeding on the active ethanolic A. tridentata extract and the petrol extract from C. suaveolens. The relative growth rate (RGR) of P. saucia larvae fed the ethanolic extract of A. tridentata in artificial diet was significantly lower than that in larvae fed diet with the petrol extract of C. suaveolens and larvae on control diet. Dietary utilization was significantly lower for larvae fed the A. tridentata extract. Results of a field trial indicated that a single treatment of A. tridentata extract at the equivalent of 0.2 g/ml could protect cabbage significantly better than the carrier solvent (30% aq ethanol) or distilled water as measured by a visual damage estimate. An insecticide standard, deltamethrin (17.9 µg/1 with 0.4% Superspred TM ), suppressed pest damage significantly better than the A. tridentata-extract treatment. A residual oviposition deterrency to Pieris rapae was found in the field results. Caged experiments in the laboratory confirmed the contact oviposition deterrency of the A. tridentata extract at 0.2 g/ml. Offspring of field-collected P. saucia larvae grew 2.5-fold heavier than larvae from the laboratory colony. However, diet with the A. tridentata extract inhibited both field-collected and laboratory reared saucia larvae equally when compared to their respective controls fed untreated diet. In summary, these results indicate the potential benefit of using specific unrefined plant extracts for growth inhibitors and oviposition deterrents against insect pests. The contribution of individual phytochemicals in the A. tridentata ethanolic extract to growth inhibition or oviposition deterrency is currently speculative.
Land and Food Systems, Faculty of
Graduate

Yield fluctuation in Vicia faba is due primarily to reproductive failure, which can occur as a result of bud abortion, flower shedding or pod and ovule abortion (Gates et al., 1983b). Flower drop, which accounts for the major proportion of total reproductive loss, contributes most to the reduction in potential yield. Application of artificial plant growth retardants (EL500, JF 10405 and Alar) were shown to increase the yield of broad beans (Vicia faba L. major cv. Threefold White), by up to 52%, mostly due to increased pod set. Experiments involving the application of plant growth substances directly to the flowers, suggested that increase in pod set was due to changes in intrinsic hormone levels. In particular, high levels of cytokinin are required at the pedicel:peduncle junction pre-pollination, to allow successful initiation of potential sinks, while increased levels of auxin are required after pollination in conjunction with cytokinin to allow cell division, pod expansion and vascular differentiation. Application of anti-gibberellin plant growth retardants appeared to alter internal hormone ratios, affecting the distribution of dry matter production during early flowering, i.e. treated plants had an increased root to stem dry matter growth rate. This suggested an increased cytokinin:gibberellin ratio had been achieved. Although it was shown that pod set could be enhanced by the application of either plant growth retardants and/or plant growth substances, yield was not always as high as anticipated due to increased levels of pod drop. Further applications of cytokinin and auxin to the pods reduced this drop. It followed therefore, that further applications could dramatically increase the yield potential of the plant due to better distribution of assimilates to pods. However, it would appear that the plant also suffers from source limitations and until these are successfully overcome, yield instability in the field environment is still likely.

Thesis (MSc)--Stellenbosch University, 2012.
ENGLISH ABSTRACT: Plant growth promoting substances (PGPS) are emerging as useful tools in the investigation of important plant growth traits. Two PGPS, smoke-water derived from burning plant material and a synthetic strigolactone analogue, GR24, have been reported to regulate a wide variety of developmental and growth processes in plants. These PGPS are beginning to receive considerable attention in the area of improving plant biomass yield and production. Variation in growth between plants is a major impediment towards the complete understanding of the intrinsic processes that control biomass production. Callus cultures of the model plant Arabidopsis thaliana could overcome some of these hindrances. However, the suitability of these callus cultures as a model system for plant biomass production must be established first. This study aimed at using A. thaliana callus cultures as a platform to study the plant growth promoting activities of smoke-water and GR24. The first part of this study was conducted to develop an optimal protocol for inducing A. thaliana callus formation. Wild-type A. thaliana Col-O, as well as strigolactone deficient and insensitive mutants (max1-1, max2-1, max2-2, max3-9 and max4-1) were cultured for callus induction. Hypocotyl and leaf explants were cultured onto MS media supplemented with different hormone concentrations of 2,4-D and kinetin (2:2 mg/L 2,4-D:kinetin and 0.5:0.05 mg/L 2,4-D:kinetin). Both media proved suitable for callus induction of all genotypes, with max1-1 showing the highest efficiency (83.33% and 92.22%) of callus induction. Calli were then used as a platform for future investigations into the effects of smoke-water and GR24. Secondly, this study examined the effects of smoke-water and GR24 on wild-type A. thaliana Col-O callus. Basic physiological studies were conducted to determine if these two compounds would positively affect callus growth, as was shown in previous studies using whole plants. Calli cultivated on MS media containing the two different hormone concentrations were transferred onto the same fresh MS medium, supplemented with either smoke-water or GR24. Growth promotion by smoke-water and GR24 in calli was characterized by a significantly increased mass (biomass). Calli were additionally transferred onto MS medium containing either auxin only or kinetin only and supplemented with GR24 or smoke-water. In the auxin only system, increased mass was recorded for both GR24 and smoke-water treatments, while these two compounds seemed to reduce growth in the kinetin only system. The positive growth stimulatory effect observed for the auxin only system could be attributed to the synergistic relationship between auxin and strigolactones, whilst the reduced mass in the latter system could be due to the antagonistic interaction between strigolactones and cytokinins. Finally, this study has discovered a dual role of strigolactones in biomass accumulation and adventitious root formation for Arabidopsis thaliana callus. On an auxin- and cytokinin-free MS medium supplemented with GR24, calli of Arabidopsis thaliana strigolactone deficient mutants (max1-1 and max4-1) and the wild-type Col- O, but not the strigolactone response mutant (max2-2), showed enhanced biomass accumulation. In addition to this, the max4-1 mutant and wild-type Col-O demonstrated enhanced adventitious rooting, which was not apparent in max2-2. Together these data suggested that the biomass accumulation and the adventitious rooting activities of GR24 in Arabidopsis thaliana calli are controlled in a MAX2- dependent manner. The interaction between strigolactone, auxin and cytokinin signalling pathways in regulating these responses appears to be complex. Gene expression profiling showed regulation of stress-related genes such as B-box transcription factors, CALCINEURIN B-LIKE and RAP4.2 Genes encoding hormones associated with stress (ABA, ethylene) and defence mechanisms (JA) were upregulated. Expression of stress related genes indicated clues on some kind of stress mediation that might be involved during the regulation of the rhizogenic response. Conversely, smoke-water treatment could not enhance the biomass of the calli and nor could it induce adventitious rooting in the absence of auxin and cytokinin. This observation strongly emphasized the distinct roles of these two compounds, as well as the importance of the interaction and ratio of auxin and cytokinin in callus growth. This study has demonstrated a novel role of strigolactones in plant growth and development, i.e. enhancement of biomass production in callus cultures. Secondly the enhanced adventitious rooting ability is in agreement with recently published literature on the role of strigolactones in regulating root architecture. In vitro callus production is advantageous to plant sciences. It creates an opportunity for increasing plant material for cultivation and offers the use of cell cultures that accurately mimic specific growth responses. It could greatly contribute to the study of intricate regulatory and signalling pathways responsible for growth and development in plants. Because the regulation of plant biomass production is very complex and the molecular mechanisms underlying the process remain elusive, it is of paramount importance that further work be done in order to gain more in-depth insights and understanding of this aspect and subsequently improve efficiency and returns when applying biotechnology tools on commercially important crop plants.
AFRIKAANSE OPSOMMING: Verbindings wat plantgroei bevorder (PGBV) het as nuttige alternatief ontstaan om plant groei te ondersoek. Rook-water, afkomstig van verbrande plant material, en ‘n sintetiese strigolaktoon analoog, GR24, wat ‘n α, β-onversadigde furanoon funksionele groep in gemeen het, is vir die regulering van ‘n wye verskeidenheid ontwikkelings- en groei prosesse in plante verantwoordelik. Tans ontvang hierdie PGBVs aansienlik aandag in die area van die verbetering van plant biomassa opbrengs en -produksie. Die variasie in groei tussen plante is ‘n groot hindernis om die intrinsieke prosesse wat biomass produksie beheer, volledige te verstaan. Deur gebruik te maak van kallus kulture van die model plant Arabidopsis thaliana kan van hierdie hindernisse oorkom word. Tog moet die geskiktheid van kallus kulture as ‘n model sisteem vir plant groei biomass produksie eers gevestig word. Die doel van hierdie studie was om A. thaliana kallus kulture as ‘n platform vir die studie van die plantgroei bevorderingsaktiwiteite van rook-water en GR24 te gebruik. Die eerste deel van die studie is uitgevoer ten einde ‘n optimale protokol vir die induksie van A. thaliana kallus produksie te ontwikkel. Wilde tipe Col-0, asook strigolaktoon afwesige en onsensitiewe mutante (max1-1, max2-1, max2-2, max3-9 en max4-1) is vir kallus induksie gekultiveer. Hipokotiel en blaar eksplante is op MS medium wat verskillende hormoon konsentrasies van 2,4-D en kinetien (2:2 mg/L 2,4-D:kinetien en 0.5:0.05 mg/L 2,4-D:kinetien) bevat, oorgedra. Beide media was geskik vir kallus induksie van al die genotipes, met max1-1 wat die hoogste effektiwiteit (83.33% en 92.22%) van kallus induksie getoon het. Kalli is daarna as ‘n platform vir toekomstige navorsing i.v.m die effek van rook-water en GR24 gebruik. Tweedens ondersoek die studie die effek van rook-water en GR24 op wilde tipe Col-0 kallus. Basiese fisiologiese studies is uitgevoer om te bepaal of die twee verbindings ‘n positiewe effek op kallus groei toon soos aangedui in vorige studies waar intakte plante gebruik is. Kallus wat op MS medium wat die twee verskillende hormoon konsentrasies bevat gekultiveer was, is op dieselfde vars MS medium, wat addisioneel óf rook-water óf GR24 bevat, oorgedra. Die stimulering van groei van kalli deur rook-water en GR24 is deur ‘n merkwaardige toename in massa (biomassa) gekenmerk. Kallus is additioneel op MS medium wat slegs óf ouksien óf kinetin bevat (gekombineer met GR24 of rook-water behandeling), oorgedra. In die sisteem waar slegs ouksien toegedien is, is ‘n toename in massa waargeneem vir beide GR24 en rook-water behandelinge. In teenstelling hiermee, het die twee verbindings in die sisteem waar slegs kinetin toegedien is, ‘n vermindering in groei meegebring. Die positiewe groei stimulerende effek wat waargeneem is vir die sisteem waar slegs ouksien toegedien is, kan toegedra word aan die sinergistiese verhouding tussen die ouksien en strigolaktone; terwyl die verlaagde massa in die laasgenoemde sisteem aan die antagonistiese interaksie tussen strigolaktone en sitokiniene toegedra kan word. Laastens het hierdie studie het ‘n gelyktydige rol van strigolaktone vir biomassa akkumulasie en bywortelvorming in Arabidopsis thaliana kallus ontdek. Kallus van A. thaliana strigolaktoon afwesige mutante (max1-1 en max4-1) en die wilde tipe Col-0 (maar nie die strigolaktoon reagerende mutant (max2-2) het op ‘n ouksien en sitokinien vrye MS medium wat GR24 bevat ‘n verhoogde biomassa akkumulasie getoon. Die max4-1 mutant en wilde tipe Col-0 het verhoogde bywortelvorming getoon, wat nie so opmerklik by max2-2 was nie. Hierdie data het tesame voorgestel dat die biomassa akkumulasie en die bywortelvormingsaktiwiteite van GR24 in Arabidopsis thaliana kallus op ‘n MAX2-afhanklike wyse beheer word. Die interaksie tussen strigolaktoon, ouksien en sitokinien sein transduksie paaie vir die regulering van hierdie reaksies blyk kompleks te wees. Die geen uitdrukkingsprofiel het die regulering van stres verwante gene soos B-boks transkripsie faktore, CALCINEURIN B-LIKE en RAP4.2, getoon. Gene wat vir hormone wat aan stres (ABA, etileen) en verdedigingsmeganismes (JA) verwant is, is opgereguleer. Die uitdrukking van stress verwante gene dui op tekens van ‘n ander tipe stres bemiddeling wat dalk by die regulering van die risogeniese reaksie betrokke kan wees. In teenstelling, rook water behandeling kon nie die kallus biomassa verhoog nie en dit kon ook nie die bywortelingvorming in die afwesigheid van ouksien en sitokiniene induseer nie. Hierdie waarneming is ‘n sterk bevestiging vir die uitsonderlike rol van die twee verbindings, asook die belang van die interaksie en verhouding van ouksien en sitokinine vir die groei van kallus. Hierdie studie toon op ‘n nuwe rol van strigolaktoon in plant groei en ontwikkeling, d.w.s die verhoogde biomassa produksie in kallus kulture. Tweedens, die verhoogde bywortelvormingsvermoë is in ooreenstemming met literatuur wat onlangs gepubliseer is i.v.m die rol van strigolaktone in die regulering van wortel argitektuur. Die in vitro produksie van kallus is voordelig in plant wetenskappe. Dit skep ‘n geleentheid vir die vermeerdering van plant materiaal vir kultivering en bied die gebruik van selkulture wat spesifieke groei reaksies op ‘n merkwaardige wyse akkuraat namaak. Dit kan grootliks bydra tot die studie van die delikate regulatoriese en sein transduksie paaie wat vir groei en ontwikkeling van plante verantwoordelik is. Aangesien die regulering van plant biomassa produksie baie kompleks is en die molekulêre meganismes vir die proses onbekend bly is dit van grootskaalse belang dat meer werk gedoen word om ‘n meer in diepte insig en kennis van die aspekte en gevolglike verbetering van effektiwiteit en wins te kry deur die toepassing van biotegnologiese metodes op die gewas plante wat van kommersiêle belang is.

The use of reserve substances by maize during germination may depend on various factors, in-cluding genotypic and abiotic ones. The aim of the study was to establish the changes in the germination characteristics, starch content and reserve substances mobilization of various maize hybrids under the in-fluence of supraoptimale temperature and genistifoliosides. The heat stress promoted an increase in the metabolic efficiency of maize germination and led to a decrease in the starch content in the seeds. These changes were mostly dependent on the maize hybrid. The seeds pretreatment with genistifoliosides al-lowed removing the growth inhibition caused by increased temperature.

The article discusses the use of former agricultural lands for afforestation. The fertility of these lands is reduced, low biological activity of soils is noted, the content of substances inhibiting the growth of woody plants is observed. The presence of a compacted subsurface layer contributes to the fact that the root systems of trees are formed by surface and do not reach groundwater. Created forest plantations usually experience a water supply crisis, they die off in dry years, they are easily exposed to diseases and pests. Possible ways of solving problems associated with afforestation in this category of land are suggested.

The basis of microbial means of plant protection against diseases is live cultures of microorganisms with high virulence and their metabolic products. The leading role in the biological control of plant diseases is assigned to microscopic fungi. A special place is occupied by the genus Trichoderma Pers. ex Fr. The advantages are a high growth rate, a wide range of antifungal activity, and simple equipment for cultivation on an industrial scale. The biopreparation production technology constitutes the cultivation of the fungus-producer in a liquid nutrient medium in a bioreactor or on a microbiological shaker for 72-96 hours. An important step in obtaining effective biopreparations is the selection of the optimal nutrient medium for cultivating the bioagent. Modification of nutrient media according to the main sources of nutrition of microorganisms (carbon, nitrogen) promotes the formation of biologically active substances that have an inhibitory effect on phytopathogens. This action can be strengthened or weakened. During the evaluation of the fungicidal action spectrum of the liquid biopreparation Gliocladin-SC (the active substance is the fungus Trichoderma virens Miller, Giddens, and Foster), 18 pathogenic agents of crop diseases causative agents were identified (Scerbacova T., 2019). Several liquid nutrient media were used in the present work. When the medium composition changed according to the carbon source, in addition to chlamydospores, conidia and blastospores were formed. The zones of Sclerotinia sclerotiorum pathogens inhibition growth (Fig. 1) and Botrytis cinerea expanded, and the antifungal effect against pathogens of fruit crops Monilia cinerea and M. fructigena also increased. The preparation fabricated on the base of that nutrient medium was tested on “Krupnoplodnyi” sweet cherries variety to suppress the development of moniliosis. After two treatments with 1% concentration, the disease development reduction efficiency was 91.8% (Scerbacova T. et al., 2015). Media 2(a) Media 10 Media 11 Figure 1. Growth inhibition zones of the pathogen S. sclerotiorum with Gliocladin-SC biopreparation based on media with different compositions In the result of the conducted research, it was found that for the successful application of GliocladinSC biopreparation in plant protection against a wide range of diseases, separate balanced nutrient media for controlling different groups of pathogens are needed.

One of the effective ways to obtain new biologically active substances is the search for new strains of microorganisms - producers. The most active antagonists among microorganisms are actinobacteria: of the 10,000 known antibiotics produced by microorganisms, about 70% are of actinomycete origin. Microorganisms, including actinobacteria, are of interest as enzyme producers, in particular, for the biocontrol of phytopathogenic fungi, as plant protection preparations, as well as for the biodegradation of plant residues, as a reservoir of infection in the soil for agricultural plants, etc. The task of the research was to study the ability of strains of actinobacteria isolated from the biofilm of the “La Izvor” lake system to exhibit enzymatic activity, as well as to inhibit the growth of a number of phytopathogenic bacteria and fungi. The objects of research were representatives of 8 genera of actinobacteria isolated from the biofilm of the lake system "La Izvor", Chisinau. It was established that strain B 2.1 (genus Actinoplanes) has weak (+) amylase activity, medium (++) lipase and high (+++) catalase activity. Strain B 3.1 (genus Frankia) showed weak (+) catalase and moderate (++) amylase activity. In strain B 4.1 (genus Geodermatophilus) a weak (+) catalase activity was noted, as in strain B 6.1 (genus Nocardia). The representative of the Micromonospora strain B 5.1 was characterized by medium (++) catalase and weak (+) amylase activity. Four strains are representatives of the river. Streptomyces showed weak (+) amylase activity, 2 strains of this genus (B 8.1 and B 8.4) also had weak (+) catalase activity, and only strain B 8.1 showed medium (++) lipase activity. Low antibacterial activity was observed in strain B 5.1 (genus Micromonospora) - the diameter of the growth inhibition zones of Agrobacterium tumefaciens, Bacillus subtilis, Clavibacter michiganensis, Erwinia carotovora - 9.0 - 14.0 mm. From the strains of genus Streptomyces, only strain B 8.3 had the ability to inhibit the growth of 5 phytopathogenic bacteria with a zone diameter of 12.0-16.0 mm. It was found the ability to inhibit the growth of the phytopathogen Alternaria alternata by the strains B 2.1, B 4.1, B 8.3, and B 8.4 (zone diameter - 15.0 - 20.0 mm). The growth of Fusarium solani was retarded by 6 strains (zones from 10.0 to 20.0 mm); Fusarium oxysporum - by 2 strains (zones 12.0-14.0 mm); and Aspergillus niger – by 4 strains (zones 12.0 - 16.0 mm). Thus, the conducted studies have shown that new strains of actinobacteria isolated from the biofilm of the “La Izvor” lake system, Chisinau, which have shown amylase, catalase, and lipase activity, as well as having the ability to inhibit the growth of a number of phytopathogens, are of particular interest and can replenish the National Collection of Non Pathogenic Microorganisms.

We have carried out the synthesis and screening of soybean growth regulators in a series of substituted thieno[2,3-b]pyridines. The compounds, which have a high growth-regulating effect, were detected. According to the field tests, the substances have a positive effect in formation of the yield structure and provide seed quality.

Microalgae are in focus of extensive study due to their abundance and important role in equilibration of the global ecosystem. Living organisms communicate through nano-sized membrane-enclosed particles which are continuously shed by cells but can also be fabri-cated artificially. In this work we examined the effect of hybridosomes composed from soyabean lecithin, aqueous solution containing substances from spruce needles and glyc-erol and hybridosomes composed from soyabean lecithin, ultraclean water and hemp oil on the number density of microalgae Phaeodactylum tricornutum in culture. We measured the number density of microalgae by flow cytometry and the number density and hydro-dynamic diameter of small particles in the samples by interferometric light microscopy. We observed considerable increase of the number density of microalgae with respect to control (untreated) samples after three days, which was connected to the amount of the material added. Addition of membrane-enclosed particles had a favourable effect on the microalgae growth. Microalgae proved a convenient system for in vitro studies of the ef-fects of substances. Keywords: Phaeodactylum tricornutum; Hybridosomes; Liposomes; Nanoalgosomes; Ex-tracellular vesicles; Small cellular particles; Microalgae

The effect of biologically active substances (BAS) Siliplant, Epin-Extra and Ekofus on the height and biomass of soybean plants was studied in a field experiment carried out at the Field Experimental Station of the Russian State Agricultural University named after K.A. Timiryazev in 2020. The treatment was carried out at the beginning of flowering according to the method developed by the authors of BAS (Epin-Extra - 40 ml / ha, Siliplant - 1.5 l / ha and Ekofus - 3 l / ha). The growth of plants in height in the variants with biologically active substances significantly exceeded the control by 10,6 – 11,4 %. The maximum plant biomass was registered during the period of seed filling and was significantly higher than the control by 11,1 - 11,4 %.

The antagonistic activity of 11 non-phytopathogenic isolates of microscopic fungi was studied. According to the results of the studies, isolates of microscopic fungi TV, T4 and 6G2, active against phytopathogenic bacteria, inhibiting the growth of mycelium of phytopathogenic fungi, were selected for further research in order to include phytoprotective action in biological preparations. Microscopic fungi TV and T4 were identified as representatives of the genus Trichoderma, micromycete 6G2 was identified as representative of the genus Penicillium, subgenus Eupenicillium.

Laboratory and field experiments evidence that silicon fertilizers contribute to plant tolerance to unfavorable growth conditions: drought, frost, salinity, heavy metal contamination, and others. Silicon-induced underlying mechanisms include thickening of the epidermal layer, enhanced root system development, chemical stability of the DNA, RNA, and chlorophyll molecules, improved transport and redistribution of elements, as well as activation of defense system in plants against oxidative damage. Application of Si fertilizers and biostimulators promoted reducing crop losses and increasing yield of rice, wheat, barley, soya, potatoes and others under drought and frost conditions.

Wastewater sludge contains essential nutrients for plant growth and is frequently used as fertilizer in European agriculture. Sludge contains elevated concentrations of heavy metals, microplastics, and other substances that may pose potential risks to human health and the environment. Nevertheless, dried pelletized sludge emerges as a viable product for fertilizing short-rotation poplar plantations within a circular model, enabling nutrient recycling and converting waste into a valuable resource to enhance biomass production for different markets. In Hillebola, central Sweden, we demonstrated the application of dried pelletized sludge to pilot plantations with climate-adapted Populus trichocarpa clones. The trial was established in four blocks with four treatments three years after the poplar trees were planted. The treatments were: mineral NPK fertilizer + soil cultivation between poplar rows, dried pelletized sludge + soil cultivation, no fertilization + soil cultivation only, and control (no treatments). The effect of fertilization on poplar growth was evaluated two years later, after the fifth growing season. The results showed a significantly improved basal area increment in NPK and sludge treatments compared to the control. The ground vegetation inventory revealed substantial differences in weed biomass between control and cultivated plots. Control plots contained double the amount of aboveground grass and herbaceous biomass (8.6 ton ha-1 ) compared to cultivated and cultivated + fertilized plots. The low-intensity Nordic-Baltic poplar establishment practices allow for a substantial amount of ground vegetation to develop until the canopy closure, potentially contributing to the soil carbon pool more than it is usually recognized when modeling carbon balances in short-rotation poplar plantations, which is the theme of our next report.