Drought-induced molecular changes in crown of various barley phytohormone mutants.

One of the main signal transduction pathways that modulate plant growth and stress responses, including drought, is the action of phytohormones. Recent advances in omics approaches have facilitated the exploration of plant genomes. However, the molecular mechanisms underlying the response in the crown of barley, which plays an essential role in plant performance under stress conditions and regeneration after stress treatment, remain largely unclear. The objective of the present study was the elucidation of drought-induced molecular reactions in the crowns of different barley phytohormone mutants. We verified the hypothesis that defects of gibberellins, brassinosteroids, and strigolactones action affect the transcriptomic, proteomic, and hormonal response of barley crown to the transitory drought influencing plant development under stress. Moreover, we assumed that due to the strong connection between strigolactones and branching the hvdwarf14.d mutant, with dysfunctional receptor of strigolactones, manifests the most abundant alternations in crowns and phenotype under drought. Finally, we expected to identify components underlying the core response to drought which are independent of the genetic background. Large-scale analyses were conducted using gibberellins-biosynthesis, brassinosteroids-signaling, and strigolactones-signaling mutants, as well as reference genotypes. Detailed phenotypic evaluation was also conducted. The obtained results clearly demonstrated that hormonal disorders caused by mutations in the HvGA20ox2, HvBRI1, and HvD14 genes affected the multifaceted reaction of crowns to drought, although the expression of these genes was not induced by stress. The study further detected not only genes and proteins that were involved in the drought response and reacted specifically in mutants compared to the reaction of reference genotypes and vice versa, but also the candidates that may underlie the genotype-universal stress response. Furthermore, candidate genes involved in phytohormonal interactions during the drought response were identified. We also found that the interplay between hormones, especially gibberellins and auxins, as well as strigolactones and cytokinins may be associated with the regulation of branching in crowns exposed to drought. Overall, the present study provides novel insights into the molecular drought-induced responses that occur in barley crowns.

Characterising Biological and Physiological Drought Signals in Diverse Parents of a Wheat Mapping Population.

Water deficit affects the growth as well as physiological and biochemical processes in plants. The aim of this study was to determine differences in physiological and biochemical responses to drought stress in two wheat cultivars-Chinese Spring (CS) and SQ1 (which are parents of a mapping population of doubled haploid lines)-and to relate these responses to final yield and agronomic traits. Drought stress was induced by withholding water for 14 days, after which plants were re-watered and maintained until harvest. Instantaneous gas exchange parameters were evaluated on the 3rd, 5th, 10th, and 14th days of seedling growth under drought. After 14 days, water content and levels of chlorophyll a+b, carotenoids, malondialdehyde, soluble carbohydrates, phenolics, salicylic acid, abscisic acid (ABA), and polyamines were measured. At final maturity, yield components (grain number and weight), biomass, straw weight, and harvest index were evaluated. Physiological and biochemical parameters of CS responded more than those of SQ1 to the 14-day drought, reflected in a greater reduction in final biomass and yield in CS. Marked biochemical differences between responses of CS and SQ1 to the drought were found for soluble carbohydrates and polyamines. These would be good candidates for testing in the mapping population for the coincidence of the genetic control of these traits and final biomass and yield.

Comparative Assessment of Lignan Profiling and Biological Activities of Schisandra henryi Leaf and In Vitro PlantForm Bioreactor-Grown Culture Extracts.

This research's scope encompassed biotechnological, phytochemical, and biological studies of Schisandra henryi, including investigations into its in vitro microshoot culture grown in PlantForm bioreactors (temporary immersion systems, TISs), as well as extracts from leaves of the parent plant, focusing on anti-inflammatory, antioxidant, anticancer, and antimicrobial activities. The phytochemical analysis included the isolation and quantification of 17 compounds from dibenzocyclooctadiene, aryltetralin lignans, and neolignans using centrifugal partition chromatography (CPC), HPLC-DAD, and UHPLC-MS/MS tandem mass spectrometry with triple quadrupole mass filter methods. Higher contents of compounds were found in microshoots extracts (max. 543.99 mg/100 g DW). The major compound was schisantherin B both in the extracts from microshoots and the leaves (390.16 and 361.24 mg/100 g DW, respectively). The results of the anti-inflammatory activity in terms of the inhibition of COX-1, COX-2, sPLA2, and LOX-15 enzymes indicated that PlantForm microshoot extracts showed strong activity against COX-1 and COX-2 (for 177 mg/mL the inhibition percentage was 76% and 66%, respectively). The antioxidant potential assessed using FRAP, CUPRAC, and DPPH assays showed that extracts from microshoot cultures had 5.6, 3.8, and 3.3 times higher power compared to extracts from the leaves of the parent plant, respectively. The total polyphenol content (TPC) was 4.1 times higher in extracts from the in vitro culture compared to the leaves. The antiproliferative activity against T-cell lymphoblast line Jurkat, breast adenocarcinoma cultures (MCF-7), colon adenocarcinoma (HT-29), and cervical adenocarcinoma (HeLa), showed that both extracts have considerable effects on the tested cell lines. The antimicrobial activity tested against strains of Gram-positive and Gram-negative bacteria and fungi showed the highest activity towards H. pylori (MIC and MBC 0.625 mg/mL).

KAR1-induced dormancy release in Avena fatua caryopses involves reduction of caryopsis sensitivity to ABA and ABA/GAs ratio in coleorhiza and radicle.

MAIN CONCLUSION: The dormancy release by KAR1 is associated with a reduction of coleorhiza and radicle sensitivity to ABA as well as with reduction the ABA/GAs ratio in the coleorhiza, by a decrease content of ABA, and in the radicle, by a decrease the ABA and an increase of the GAs contents. Both, karrikin 1 (KAR1) and gibberellin A3 (GA3), release dormancy in Avena fatua caryopses, resulting in the emergence of coleorhiza (CE) and radicle (RE). Moreover, KAR1 and GA3 stimulate CE and RE in the presence of abscisic acid (ABA), the stimulation being more effective in CE. The stimulatory effects of KAR1 and GA3 involve also the CE and RE rates. A similar effect was observed at KAR1 concentrations much lower than those of GA3. KAR1 increased the levels of bioactive GA5 and GA6 in embryos and the levels of GA1, GA5, GA3, GA6 and GA4 in radicles. The stimulatory effect of KAR1 on germination, associated with increased levels of gibberellins (GAs) and reduced levels of ABA in embryos, was counteracted by paclobutrazol (PAC), commonly regarded as a GAs biosynthesis inhibitor. Consequently, KAR1 decreased the ABA/GAs ratio, whereas PAC, used alone or in combination with KAR1, increased it. The ABA/GAs ratio was reduced by KAR1 in both coleorhiza and radicle, the effect being stronger in the latter. We present the first evidence that KAR1-induced dormancy release requires a decreased ABA/GAs ratio in coleorhiza and radicle. It is concluded that the dormancy-releasing effect of KAR1 in A. fatua caryopses includes (i) a reduction of the coleorhiza and radicle sensitivity to ABA, and (2) a reduction of the ABA/GAs ratio (i) in the coleorhiza, by decreasing the ABA content, and (ii) in the radicle, by decreasing the ABA and increasing the content GAs, particularly GA1. The results may suggest different mechanisms of dormancy release by KAR1 in monocot and dicot seeds.

The yield of common buckwheat (Fagopyrum esculentum Moench) depends on the genotype but not on the Pin-to-Thrum ratio.

Common buckwheat has a complicated flowering biology. It is characterized by a strong self-incompatibility resulting from heterostyly, i.e. the occurrence of two types of flowers: Pin and Thrum, differing in the length of pistils and stamens. Fertilization occurs only as a result of cross-pollination between these morphs. Suspicions exist that the disturbed ratio between plants producing Pin and Thrum flowers (with the latter type generating more seeds) causes low seed yield. The aim of the study was to analyze: (1) the ratio between plants with Pin and Thrum morphs, (2) flower and seed production, as well as abortion of flowers, (3) the composition of nectar collected at an early flowering stage and during full flowering. The study was performed under semi-controlled and field conditions on six Polish accessions. The results indicated that under semi-controlled conditions the Pin-to-Thrum ratio was indeed disproportionate; such a phenomenon is called anisoplethy. In the field, however, the Pin-to-Thrum ratio was well-balanced (isoplethy). The plants with both morphs aborted a similar percentage of flowers and produced a comparable number of empty seeds. The number of flowers, their abortion, and ripe seed production were independent of flower type, however, they were genotypically controlled. A strong correlation between the number of flowers produced by a plant, flower abortion and the number of empty seeds was found. The percentage of aborted flowers correlated positively with the weight of ripe seeds. Nectar composition was similar for all buckwheat genotypes, but we found some differences in the amount of individual sugars depending on the blooming stage. In the majority of accessions, the nectar produced at the early blooming stage was characterized by a greater mass and volume, and contained more individual sugars than at the full-flowering stage.

The Effect of Stimulants on Nectar Composition, Flowering, and Seed Yield of Common Buckwheat (Fagopyrum esculentum Moench).

Common buckwheat is a valuable plant producing seeds containing a number of health-promoting compounds and elements. Buckwheat does not contain gluten and is characterized by an excellent composition of amino acids. This species is also a melliferous plant. Despite many advantages, the area of buckwheat cultivation is decreasing due to unstable yields. One of the reasons for low seed yield is its sensitivity to drought, high temperatures, and assimilate deficiencies. These factors have a significant impact on the nectar composition, which is important for visiting pollinators and thus for pollination. High temperature during flowering increases the degeneration of embryo sacs and embryos, which is high anyway (genetic determination) in common buckwheat. This phenomenon seems to be unbreakable by breeding methods. The authors aimed to determine whether stimulants commonly used in agriculture could increase the seed yield of this plant species. The aim of the work was to choose from eight different stimulants the most effective one that would improve the seed yield of two accessions of common buckwheat by increasing the efficiency of nectar production and reducing the number of empty seeds. The plants were sprayed at either the beginning of flowering or at full bloom. The content of sugars and amino acids was higher in the nectar produced at the beginning of flowering. The nectar of both lines included also polyamines. The level of sugars in the nectar increased mainly after spraying with the stimulants in the second phase of flowering. A positive correlation between the total amount of sugars and amino acids in the nectar and seed yield was found. All the stimulants used reduced the number of empty seeds in both accessions. Seed production in the PA15 line increased significantly under the influence of all stimulants used at the beginning of flowering, and the most effective were ASAHI SL and TYTANIT®.

NO-mediated dormancy release of Avena fatua caryopses is associated with decrease in abscisic acid sensitivity, content and ABA/GAs ratios.

MAIN CONCLUSION: NO releases caryopsis dormancy in Avena fatua, the effect being dependent on the level of dormancy. The NO effect involves also the reduction of caryopsis sensitivity to ABA and to a decrease in the ABA to GAs ratio due to a decrease in ABA levels and the lack of effect on GAs levels before germination is completed. Nitric oxide (NO) from various donors (i.e. SNP, GSNO and acidified KNO2), applied to dry caryopses or during initial germination, released primary dormancy in caryopses. Dormancy in caryopses was gradually lost during dry storage (after-ripening) at 25 °C, enabling germination at 20 °C in the dark. The after-ripening effect is associated with a decrease in NO required for germination. In addition, NO decreased the sensitivity of dormant caryopses to exogenous abscisic acid (ABA) and decreased the embryos' ABA content before germination was completed. However, NO did not affect the content of bioactive gibberellins (GAs) from non-13-hydroxylation (GA4, GA7) and 13-hydroxylation (GA1, GA3, GA6.) pathways. Paclobutrazol (PAC), commonly regarded as a GAs biosynthesis inhibitor, counteracted the dormancy-releasing effect of NO and did not affect the GAs level; however, it increased the ABA content in embryos before germination was completed. Ascorbic acid, sodium benzoate and tiron, scavengers of reactive oxygen species (ROS), reduced the stimulatory effect of NO on caryopsis germination. This work provides new insight on the participation of NO in releasing A. fatua caryopses dormancy and on the relationship of NO with endogenous ABA and GAs.

Cytotoxic and Antioxidant Activity of Hypericum perforatum L. Extracts against Human Melanoma Cells from Different Stages of Cancer Progression, Cultured under Normoxia and Hypoxia.

Oxidative stress and the hypoxic microenvironment play a key role in the progression of human melanoma, one of the most aggressive skin cancers. The aim of our study was to evaluate the effect of Hypericum perforatum extracts of different origins (both commercially available (HpEx2) and laboratory-prepared from wild grown (HpEx12) and in vitro cultured (HpEx13) plants) and hyperforin salt on WM115 primary and WM266-4 lymph node metastatic human melanoma cells cultured under normoxic and hypoxic conditions. The polyphenol content, radical scavenging activity, and hyperforin concentration were determined in the extracts, while cell viability, apoptosis, ROS production, and expression of NRF2 and HO-1, important oxidative stress-related factors, were analyzed after 24 h of cell stimulation with HpExs and hyperforin salt. We found that cytotoxic, pro-apoptotic and antioxidant effects depend on the extract composition, the stage of melanoma progression, and the oxygen level. Hyperforin salt showed lower activity than H. perforatum extracts. Our study for the first time showed that the anticancer activity of H. perforatum extracts differs in normoxia and hypoxia. Importantly, the composition of extracts of various origins, including in vitro cultured, resulting in their unique properties, may be important in the selection of plants for therapeutic application.

Seeds of Stevia rebaudiana Bertoni as a Source of Plant Growth-Promoting Endophytic Bacteria with the Potential to Synthesize Rebaudioside A.

In this study, a new strain of Pantoea vagans, SRS89, was isolated from surface-sterilized stevia seeds. The isolate was evaluated using morphological, molecular, and biochemical methods. The bacterium was 1.5 µm long, yellowish in color, and classified as Gram-negative. Whole genome sequencing of our strain revealed the presence of a 4,610,019 bp chromosome, and genome annotation resulted in the detection of 4283 genes encoding 4204 putative coding sequences. Phylogenic analysis classified the genome of our strain close to the MP7 and LMG 24199 strains of P. vagans. Functional analysis showed that the highest number of genes within the analyzed bacterium genome were involved in transcription, amino acid transport and metabolism, and carbohydrate transport and metabolism. We also identified genes for enzymes involved in the biosynthesis of carotenoids and terpenoids. Furthermore, we showed the presence of growth regulators, with the highest amount noted for gibberellic acid A3, indole-3-acetic acid, and benzoic acid. However, the most promising property of this strain is its ability to synthesize rebaudioside A; the estimated amount quantified using reversed-phase (RP)-HPLC was 4.39 mg/g of the dry weight of the bacteria culture. The isolated endophytic bacterium may be an interesting new approach to the production of this valuable metabolite.

Variation between glaucous and non-glaucous near-isogenic lines of rye (Secale cereale L.) under drought stress.

Glaucous (811, L35, and RXL10) and non-glaucous (811bw, L35bw, and RXL10bw) near-isogenic lines (NILs) of rye (Secale cereale L.) forming three pairs of inbred lines were the subject of the research. The research aimed to study the relationship between wax cover attributes and the physio-biochemical drought reactions and yield of rye NILs and to uncover the differences in drought resistance levels of these lines. The greatest differences between glaucous and non-glaucous NILs were observed in the RXL10/RXL10bw pair. Of particular note were the stable grain number and the thousand grain weight of the non-glaucous line RXL10bw under drought and the accompanying reactions, such as an approximately 60% increase in MDA and a two-fold increase in wax amount, both of which were significantly higher than in the glaucous line RXL10 and in other NILs. The surprisingly high level of MDA in the RXL10bw line requires further analysis. Moreover, additional wax crystal aggregates were found under drought conditions on the abaxial leaf surface of the glaucous lines 811 and RXL10. The use of rye NILs indicated that line-specific drought resistance could be associated with wax biosynthetic pathways involved in physiological and biochemical responses important for increased drought resistance.

Stimulation of Lignan Production in Schisandra rubriflora In Vitro Cultures by Elicitation.

The study investigated the effect of elicitation with: chitosan (CH) (200 mg/L), yeast extract (YeE) (3000 mg/L), ethephon (ETH) (25 µM/L), and methyl jasmonate (MeJA) (50 µM/L), on lignan accumulation in agitated and bioreactor (Plantform temporary immersion systems) microshoot cultures of female (F) and male (M) Schisandra rubriflora Rehd. et Wils. (Schisandraceae) lines. The elicitors were supplemented on the 10th day of culture. Biomasses were collected at 24 h and 48 h, and 4, 6, and 8 days after the addition of each elicitor. The 24 compounds from the dibenzocyclooctadiene, aryltetralin, dibenzylbutane, and tetrahydrofuran lignans and neolignans were determined qualitatively and quantitatively in biomass extracts using the UHPLC-MS/MS method. The highest total contents [mg/100 g DW] of lignans were: for CH-95.00 (F, day 6) and 323.30 (M, 48 h); for YeE 104.30 (F, day 8) and 353.17 (M, day 4); for ETH 124.50 (F, 48 h) and 334.90 (M, day 4); and for MeJA 89.70 (F, 48 h) and 368.50 (M, 24 h). In the biomass extracts of M cultures grown in bioreactors, the highest total lignan content was obtained after MeJA elicitation (153.20 mg/100 g DW). The maximum total lignan contents in the biomass extracts from agitated and bioreactor cultures were 3.29 and 1.13 times higher, respectively, than in the extracts from the non-elicited cultures. The poor understanding of the chemical composition and the lack of studies in the field of plant biotechnology of S. rubriflora emphasize the innovativeness of the research.

Does Nitrogen Fertilization Affect the Secondary Structures of Gliadin Proteins in Hypoallergenic Wheat?

One of the macronutrients indispensable for plant growth and development is nitrogen (N). It is responsible for starch and storage protein (gliadins and glutenins) biosynthesis and, in consequence, influences kernels' quality and yields. However, applying N-fertilizers increases gluten content in wheat, and it may intensify the risk of developing allergy symptoms in gluten-sensitive individuals. The purpose of our research was to analyse whether and how the elimination of N-fertilizers during the cultivation of wasko.gl- wheat (modified genotype lacking ω-gliadins) changes the secondary structures of gliadin proteins. To this aim, using the FT-Raman technique, we examined flour and gliadin protein extracts obtained from kernels of two winter wheat lines: wasko.gl+ (with a full set of gliadin proteins) and wasko.gl- (without ω-gliadin fraction) cultivated on two different N-fertilization levels-0 and 120 kg N·ha-1. On the basis of the obtained results, we proved that nitrogen fertilization does not have a major impact on the stability of the secondary structures of gliadin proteins for wasko.gl- wheat line with reduced allergenic properties. Furthermore, the results presented herein suggest the possibility of increasing the stability of glutenin structures as a result of the N-fertilization of wasko.gl- wheat line, which gives hope for its use in the production of wheat articles devoted to people suffering from diseases related to gluten sensitivity.

Endophytic bacteria from in vitro culture of Leucojum aestivum L. a new source of galanthamine and elicitor of alkaloid biosynthesis.

Leucojum aestivum is known for its ability to biosynthesize alkaloids with therapeutic properties, among which galanthamine used for the treatment of Alzheimer's disease. New sources of this alkaloid are still being explored. In this study, a novel strain PLV of endophytic bacterium Paenibacillus lautus was isolated from in vitro L. aestivum plants. We report the whole genome sequence of that strain and its capacity to produce alkaloids and growth regulators. The effect of elicitation with autoclaved bacteria on the production of alkaloids was examined. Ten alkaloids were identified in bacteria extracts: galanthamine, lycorine, ismine, lycoramine, haemanthamine, tazettine, galanthine, homolycorine, 1,2-dihydrochlidanthine, and hippeastrine. The mean contents of galanthamine and lycorine were 37.51 µg/g of dry weight (DW) and 129.93 µg/g of DW, respectively. Moreover, isolated P. lautus strain synthesized: indole-3-acetic acid, t-zeatin, c-zeatin, kinetin, gibberellin A1, abscisic acid, salicylic acid, benzoic acid. In vitro elicitation of cultures with P. lautus increased dry biomass, stimulated galanthamine and lycorine production, contributed to 8,9-desmethylenebis (oxy)-7,9 dimethoxy-crinan biosynthesis, change pigments content, and antioxidant enzymes activities. Our findings for the first time point out that galanthamine can be synthesized by an microorganism. Moreover isolated strain can be used as a new elictor of Amaryllidaceae alkaloids biosynthesis.

Physiological and Biochemical Parameters of Salinity Resistance of Three Durum Wheat Genotypes.

The area of farming lands affected by increasing soil salinity is growing significantly worldwide. For this reason, breeding works are conducted to improve the salinity tolerance of important crop species. The goal of the present study was to indicate physiological or biochemical parameters characterizing three durum wheat accessions with various tolerance to salinity. The study was carried out on germinating seeds and mature plants of a Polish SMH87 line, an Australian cultivar 'Tamaroi' (salt-sensitive), and the BC5Nax2 line (salt-tolerant) exposed to 0-150 mM NaCl. Germination parameters, electrolyte leakage (EL), and salt susceptibility index were determined in the germinating caryopses, whereas photosynthetic parameters, carbohydrate and phenolic content, antioxidant activity as well as yield were measured in fully developed plants. The parameters that most differentiated the examined accessions in the germination phase were the percentage of germinating seeds (PGS) and germination vigor (Vi). In the fully developed plants, parameters included whether the plants had the maximum efficiency of the water-splitting reaction on the donor side of photosystem II (PSII)-Fv/F0, energy dissipation from PSII-DIo/CSm, and the content of photosynthetic pigments and hydrogen peroxide, which differentiated studied genotypes in terms of salinity tolerance degree. Salinity has a negative impact on grain yield by reducing the number of seeds per spike and the mass of one thousand seeds (MTS), which can be used as the most suitable parameter for determining tolerance to salinity stress. The most salt-tolerant BC5Nax2 line was characterized by the highest PGS, and Vi for NaCl concentration of 100-150 mM, content of chlorophyll a, b, carotenoids, and also MTS at all applied salt concentrations as compared with the other accessions. The most salt-sensitive cv. 'Tamaroi' demonstrated higher H2O2 concentration which proves considerable oxidative damage caused by salinity stress. Mentioned parameters can be helpful for breeders in the selection of genotypes the most resistant to this stress.

Schisandra rubriflora Fruit and Leaves as Promising New Materials of High Biological Potential: Lignan Profiling and Effect-Directed Analysis.

The effect-directed detection (EDD) of Schisandra rubriflora fruit and leaves extracts was performed to assess their pharmacological properties. The EDD comprised TLC-direct bioautography against Bacillus subtilis, a DPPH assay, as well as α-glucosidase, lipase, tyrosinase, and acetylcholinesterase (AChE) inhibition assays. The leaf extracts showed stronger antioxidant activity than the fruit extract as well as inhibition of tyrosinase and lipase. The fruit extract was found to be extremely active against B. subtilis and to inhibit α-glucosidase and AChE slightly more than the leaf extracts. UHPLC-MS/MS analysis was carried out for the bioactive fractions and pointed to the possible anti-dementia properties of the dibenzocyclooctadiene lignans found in the upper TLC fractions. Gomisin N (518 mg/100 g DW), schisanhenol (454 mg/100 g DW), gomisin G (197 mg/100 g DW), schisandrin A (167 mg/100 g DW), and gomisin O (150 mg/100 g DW) were the quantitatively dominant compounds in the fruit extract. In total, twenty-one lignans were found in the bioactive fractions.

Changes in Endogenous Phytohormones of Gerbera jamesonii Axillary Shoots Multiplied under Different Light Emitting Diodes Light Quality.

Light quality is essential in in vitro cultures for morphogenesis process. Light emitting diodes system (LED) allows adjustment as desired and the most appropriate light spectrum. The study analyzed the influence of different LED light quality on the balance of endogenous phytohormones and related compounds (PhRC) in in vitro multiplied axillary shoots of Gerbera jamesonii. Over a duration of 40 days, the shoots were exposed to 100% red light, 100% blue light, red and blue light at a 7:3 ratio with control fluorescent lamps. Every 10 days plant tissues were tested for their PhRC content with the use of an ultra-high performance liquid chromatography (UHPLC). Shoots' morphometric features were analyzed after a multiplication cycle. We identified 35 PhRC including twelve cytokinins, seven auxins, nine gibberellins, and seven stress-related phytohormones. Compounds content varied from 0.00052 nmol/g to 168.15 nmol/g of dry weight (DW). The most abundant group were stress-related phytohormones (particularly benzoic and salicylic acids), and the least abundant were cytokinins (about 370 times smaller content). LED light did not disturb the endogenous phytohormone balance, and more effectively mitigated the stress experienced by in vitro grown plants than the fluorescent lamps. The stress was most effectively reduced under the red LED. Red and red:blue light lowered tissue auxin levels. Blue LED light lowered the shoot multiplication rate and their height, and induced the highest content of gibberellins at the last stage of the culture.

A Possible Mode of Action of Methyl Jasmonate to Induce the Secondary Abscission Zone in Stems of Bryophyllum calycinum: Relevance to Plant Hormone Dynamics.

Plants can react to environmental stresses through the abscission of infected, damaged, or senescent organs. A possible mode of action of methyl jasmonate (JA-Me) to induce the formation of the secondary abscission zone (SAZ) in the stems of Bryophyllum calycinum was investigated concerning plant hormone dynamics. Internode segments were prepared mainly from the second or third internode from the top of plants with active elongation. JA-Me applied to the middle of internode segments induced the SAZ formation above and below the treatment after 5-7 days. At 6 to 7 days after JA-Me treatment, the above and below internode pieces adjacent to the SAZ were excised and subjected to comprehensive analyses of plant hormones. The endogenous levels of auxin-related compounds between both sides adjacent to the SAZ were quite different. No differences were observed in the level of jasmonic acid (JA), but the contents of 12-oxo-phytodienoic acid (OPDA), a precursor of JA, and N-jasmonyl-leucine (JA-Leu) substantially decreased on the JA-Me side. Almost no effects of JA-Me on the dynamics of other plant hormones (cytokinins, abscisic acid, and gibberellins) were observed. Similar JA-Me effects on plant hormones and morphology were observed in the last internode of the decapitated growing plants. These suggest that the application of JA-Me induces the SAZ in the internode of B. calycinum by affecting endogenous levels of auxin- and jasmonate-related compounds.

Anatomical and hormonal factors determining the development of haploid and zygotic embryos of oat (Avena sativa L.).

A critical step in the production of doubled haploids is a conversion of the haploid embryos into plants. Our study aimed to recognize the reasons for the low germination rate of Avena sativa haploid embryos obtained by distant crossing with maize. Oat cultivars of 'Krezus' and 'Akt' were investigated regarding embryo anatomy, the endogenous phytohormone profiles, and antioxidant capacity. The zygotic embryos of oat were used as a reference. It was found that twenty-one days old haploid embryos were smaller and had a less advanced structure than zygotic ones. Morphology and anatomy modifications of haploid embryos were accompanied by extremely low levels of endogenous auxins. Higher levels of cytokinins, as well as tenfold higher cytokinin to auxin ratio in haploid than in zygotic embryos, may suggest an earlier stage of development of these former. Individual gibberellins reached higher values in 'Akt' haploid embryos than in the respective zygotic ones, while the differences in both types of 'Krezus' embryos were not noticed. Additionally to the hormonal regulation of haploid embryogenesis, the poor germination of oat haploid embryos can be a result of the overproduction of reactive oxygen species, and therefore higher levels of low molecular weight antioxidants and stress hormones.

Impacts of elicitors on metabolite production and on antioxidant potential and tyrosinase inhibition in watercress microshoot cultures.

The study has proved the stimulating effects of different strategies of treatments with elicitors on the production of glucosinolates (GSLs), flavonoids, polyphenols, saccharides, and photosynthetic pigments in watercress (Nasturtium officinale) microshoot cultures. The study also assessed antioxidant and anti-melanin activities. The following elicitors were tested: ethephon (ETH), methyl jasmonate (MeJA), sodium salicylate (NaSA), and yeast extract (YeE) and were added on day 10 of the growth period. Cultures not treated with the elicitor were used as control. The total GSL content estimations and UHPLC-DAD-MS/MS analyses showed that elicitation influenced the qualitative and quantitative profiles of GSLs. MeJA stimulated the production of gluconasturtiin (68.34 mg/100 g dried weight (DW)) and glucobrassicin (65.95 mg/100 g DW). The elicitation also increased flavonoid accumulation (max. 1131.33 mg/100 g DW, for 100 µM NaSA, collection after 24 h). The elicitors did not boost the total polyphenol content. NaSA at 100 µM increased the production of total chlorophyll a and b (5.7 times after 24 h of treatment), and 50 µM NaSA caused a 6.5 times higher production of carotenoids after 8 days of treatment. The antioxidant potential (assessed with the CUPRAC FRAP and DPPH assays) increased most after 24 h of treatment with 100 µM MeJA. The assessment of anti-melanin activities showed that the microshoot extracts were able to cause inhibition of tyrosinase (max. 27.84% for 1250 µg/mL). KEY POINTS: • Elicitation stimulated of the metabolite production in N. officinale microshoots. • High production of pro-health glucosinolates and polyphenols was obtained. • N. officinale microshoots have got tyrosinase inhibition potential. • The antioxidant potential of N. officinale microshoots was evaluated.