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The contents of endogenous free and conjugated polyamines, putrescine (Put) and spermidine (Spd), were determined during 9 week of vernalization (at 5 °C) in winter wheat seedlings cultivated on Murashige and Skoog media without (MS0) and with 2 mg dm-3 zearalenone (MSZEN). At the 4th week of chilling treatment, which is sufficient to induce generative development in 30 % of plants, the marked increase in free and conjugated forms of Put and free Spd were observed. The presence of ZEN in medium significantly accelerated the vernalization. About 20 % of plants treated with ZEN flowered already after 2 weeks and 40 % after 3 weeks of chilling. Significantly higher content of free Put was determined in roots grown on MSZEN compared with MS0 during the first 5 weeks of vernalization with maximum at the 4th week. After germination, a marked decrease in free Spd content was observed both in plants grown on MS0 and MSZEN. Application of ZEN significantly slowed down the Spd decline in leaves and roots during the first and second week of vernalization. The content of Spd and its conjugates decreased in vernalized plants after 1 week of cultivation at 20 °C.

The influence of chilling (8 °C, 5 d) at two photon flux densities [PFD, L = 200 and H = 500 μmol(photon) m−2 s−1] on the gas exchange and chlorophyll fluorescence was investigated in chilling-tolerant and chilling-sensitive maize hybrids (Zea mays L., K383×K130, K185×K217) and one cultivar of field bean (Vicia faba L. minor, cv. Nadwiślański). The net photosynthetic rate (PN) for the both studied plant species was inhibited at 8 °C. PN of both maize hybrids additionally decreased during chilling. Changes in the quantum efficiency of PS2 electron transport (ΦPS2) as a response to chilling and PFD were similar to PN. Measurements of ΦPS2/ΦCO2 ratio showed that in field bean seedlings strong alternative photochemical sinks of energy did not appear during chilling. However, the high increment in ΦPS2/ΦCO2 for maize hybrids can indicate reactions associated with chill damage generation. At 8 °C the non-photochemical quenching (NPQ) increased in all plants with chilling duration and PFD. The appearance of protective (qI,p) and damage (qI,d) components of qI and a decrease in qE (energy dependent quenching) took place. NPQ components of field bean and maize hybrids differed from each other. The amount of protective NPQ (qE + qI,p) components as part of total NPQ was higher in field bean than in maize hybrids at both PFD. On 5th day of chilling, the sum of qE and qI,p was 26.7 % of NPQ in tolerant maize hybrids and 17.6 % of NPQ in the sensitive one (averages for both PFD). The increased PFD inhibited the ability of all plants to perform protective dissipation of absorbed energy. The understanding of the genotypic variation of NPQ components in maize may have implications for the future selection of plants with a high chilling tolerance. [ABSTRACT FROM AUTHOR]

Abstract The ability of zearalenone (ZEN) to stimulate the growth of haploid wheat embryos formed following the pollination of wheat spikes with maize pollen was tested. The maize pollination system was used as a model to compare the activity of ZEN with that of auxin analogues. Three solutions, each with a different concentration of ZEN (6.0, 3.0 or 1.5 μM), and a solution of 2,4-dichlorophenoxyacetic acid (control) were tested for their effect on ovary swelling, frequency of embryo formation and the ability to regenerate plants. In total, 3,105 florets of 282 spikes from five different cultivars of hexaploid winter wheat (Triticum aestivum L.) were pollinated with maize (Zea mays L. cv. Gama) pollen and treated with the ZEN solutions. The highest concentration of ZEN (6.0 μM) was the most effective in inducing ovary swelling (84 swollen ovaries/100 pollinated florets) and increasing the frequency of embryo induction (18.9 embryos/100 pollinated florets), but these embryos were severely deformed. They had low capability to germinate in vitro, while callus was easily formed and indirect regeneration of plants was possible. The lowest ZEN concentration (1.5 μM) induced ovary swelling in 42.8/100 pollinated florets and embryo growth in 3.3 out of 100 pollinated florets. The embryos were regular in shape, and almost half of them germinated in vitro while callus induction from them failed. The concentration of 3 μM ZEN had an intermediate effect. The type of response of the various wheat genotypes was similar, while frequencies were different, with cv. Izolda being the most responsive. The results show that ZEN has some of the properties of an auxin analogue, while other effects of its action are unique. It can be used in the maize pollination system of doubled haploid production to replace auxin analogues when indirect regeneration of plants via callus tissue is planned. [ABSTRACT FROM AUTHOR]

Comparative estimations of the antioxidant activity of methanolic extracts from biomasses of different types of in vitro cultures of Cistus × incanus, Verbena officinalis, Scutellaria lateriflora , and S. baicalensis and also from plant raw materials were performed. The antioxidant measurements were based on the modern assays-cupric ion reducing antioxidant capacity (CUPRAC) and quick, easy, new, cheap, and reproducible CUPRAC (QUENCHER-CUPRAC). The total extractable antioxidants (CUPRAC assay) ranged from 10.4 to 49.7 mmol (100 g) -1 of dry weight (DW) expressed as Trolox equivalent antioxidant capacity (TEAC), and the global antioxidant response (QUENCHER-CUPRAC assay) ranged from 16.0 to 79.1 mmol (100 g) -1 DW for in vitro cultures, whereas for plant raw materials the total extractable antioxidants ranged from 20.9 to 69.5 mmol (100 g) -1 DW, and the global antioxidant response ranged from 67.2 to 97.8 mmol (100 g) -1 DW. Finally, the in vitro cultures could be regarded as an antioxidant-rich alternative resource for the pharmaceutical, health food and cosmetics industries.

This study focused on the idea that the toxic effect of zearalenone (ZEA) and the protective actions of the brassinosteroid - 24-epibrassinolide (EBR) as well as selenium are dependent on its accumulation in chloroplasts to a high degree. These organelles were isolated from the leaves of oxidative stress-sensitive and stress-tolerant wheat cultivars that had been grown from grains that had been incubated in a solution of ZEA (30 μM), Na 2 SeO 4 (Se, 10 μM), EBR (0.1 μM) or in a mixture of ZEA with Se or EBR. Ultra-high performance liquid chromatography techniques indicated that ZEA was adsorbed in higher amounts in the chloroplasts in the sensitive rather than tolerant cultivar. Although the brassinosteroids and Se were also accumulated in the chloroplasts, higher levels were only found in the tolerant cultivar. The application of EBR increased the homocastasterone content, especially in the chloroplasts of the tolerant plant and after the addition of ZEA. The presence of both protectants caused a decrease in the ZEA content in studied organelles and resulted in diminishing of the oxidative stress (i.e. changes in the activity of the antioxidative enzymes). Moreover, a recovery of photosystem II and decrease in the negative impact of ZEN on Hsp90 transcript accumulation was observed in plants., (Copyright © 2019 Elsevier Masson SAS. All rights reserved.)

Despite numerous studies, the role of hormones in the induction of shoot apical meristem leading to reproductive development, especially regarding thermoperiodic plants, is still not fully understood. The key problem is separating the effects of the low temperature required for vernalization from those responsible for low temperature stress. An earlier experiment demonstrated the correlation between an increase of cytokinin level in the apical parts of winter rapeseed and the transition time into their reproductive phase during vernalization, i.e. , low temperature treatment. From data obtained from the presented experiments, this study aims to contribute to the understanding the role of cytokinins in the induction of flowering based on the grafting of vegetative apical parts of winter rapeseed (scion) on the reproductive (stock) winter and spring genotypes. On the basis of analyses carried out using ultra-high-performance liquid chromatography coupled with tandem mass spectrometry in combination with microscopic observation of changes at the apical meristem, it was indicated that the increase in the amount of trans -zeatin and trans - and cis -zeatin- O -glucoside derivatives appeared in the early stages of apex floral differentiation. During further development, the content of all investigated cytokinins passed through the maximum level followed by their decrease. The final level in reproductive apices was found to be higher than that in vegetative ones., Competing Interests: The authors declare no conflict of interest.

The putative role of cytokinins in processes leading to reproductive development of plants was investigated by analysing the shoot apical parts of a winter cultivar of oilseed rape (Brassica napus L. var. oleifera, cv. Górczański). The endogenous cytokinin levels were measured by liquid chromatography-tandem mass spectrometry (LC-MS) in the shoot apices of vegetative plants (grown at 20/17°C with a 16/8h day/night regime) and vernalized plants (56 days at 5/2°C with a 16/8h photoperiod) at different times during floral transition. During vernalization, the content of all isoprenoid cytokinins increased significantly, coinciding well with the onset of the early stages of reproductive development. Cytokinin levels reached their maxima when most of the plants became irreversibly reproductive (after 42 days of cold treatment). cis-Zeatin riboside (unequivocally identified by quadrupole-time-of-flight MS) accounted for ca. 87-89% of the total isoprenoid cytokinin content in control and vernalized plants, whilst N(6)-isopentenyladenosine ( approximately 6% in control and approximately 8% in vernalized plants) and cis-zeatin (approxiamtely 2% in control and approximately 1% in vernalized plants) were the next most abundant cytokinins. In the post-vernalization period, endogenous cytokinin levels decreased, but remained significantly higher in the reproductive plants than in the vegetative controls. These results suggest that cytokinins, especially those of the cis-zeatin type, are involved in vernalization-induced reproductive development of B. napus., (© 2012 Elsevier Ireland Ltd. All rights reserved.)

The effect of plant growth substances (IAA, 2,4-D, zeatin, kinetin, zearalenone) were studied on membrane properties of the cells of embryogenic (E) and non-embryogenic (NE) calli derived from immature inflorescences (inf) or embryos (emb) of winter wheat. Calli initiated from inflorescences show higher permeability. The ion leakage from cells of E calli was higher than from cells of NE calli. Growth regulators were used in concentrations of 2-30 mg/l (about 10-140 microM). All tested growth substances increased ion leakage from NE emb cells, IAA, zeatin and kinetin being most effective. In NE inf cells the effect of growth substances was similar as in NE emb, but much weaker. In E cells of both types (inf and emb) growth substances decreased ion leakage. Changes in the leakage of potassium and calcium ions were similar to those in total ion leakage. The uptake of labelled auxins (IAA and 2,4-D) was higher in NE cells (especially in NE inf) than in E cells. The endogenous level of IAA was higher in E cells than in NE cells and in inf cells than in emb cells. The importance of auxin in determining permeability of cell membranes is discussed.

The ability of zearalenone (ZEN) to stimulate the growth of haploid wheat embryos formed following the pollination of wheat spikes with maize pollen was tested. The maize pollination system was used as a model to compare the activity of ZEN with that of auxin analogues. Three solutions, each with a different concentration of ZEN (6.0, 3.0 or 1.5 microM), and a solution of 2,4-dichlorophenoxyacetic acid (control) were tested for their effect on ovary swelling, frequency of embryo formation and the ability to regenerate plants. In total, 3,105 florets of 282 spikes from five different cultivars of hexaploid winter wheat ( Triticum aestivum L.) were pollinated with maize ( Zea mays L. cv. Gama) pollen and treated with the ZEN solutions. The highest concentration of ZEN (6.0 microM) was the most effective in inducing ovary swelling (84 swollen ovaries/100 pollinated florets) and increasing the frequency of embryo induction (18.9 embryos/100 pollinated florets), but these embryos were severely deformed. They had low capability to germinate in vitro, while callus was easily formed and indirect regeneration of plants was possible. The lowest ZEN concentration (1.5 micrroM) induced ovary swelling in 42.8/100 pollinated florets and embryo growth in 3.3 out of 100 pollinated florets. The embryos were regular in shape, and almost half of them germinated in vitro while callus induction from them failed. The concentration of 3 microM ZEN had an intermediate effect. The type of response of the various wheat genotypes was similar, while frequencies were different, with cv. Izolda being the most responsive. The results show that ZEN has some of the properties of an auxin analogue, while other effects of its action are unique. It can be used in the maize pollination system of doubled haploid production to replace auxin analogues when indirect regeneration of plants via callus tissue is planned.

We demonstrate that differences in the endogenous biologically active levels and patterns of cytokinins depend on the organ differentiation, i. e. immature inflorescence before meiosis and immature embryo 14 days after anthesis, respectively, in winter wheat of two genotypes: Grana and Almari. Two cell lines were subjected to analysis of cytokinin contents. Higher levels of endogenous cytokinin were found in cells derived from immature embryo (E) in comparison to cells obtained from immature inflorescence (I). The levels of zeatin ryboside ([9R]Z) and benzyladenosine ([9R]BAP) were predominant and isopentenyladenine (iP) was very low for the cells E of both genotypes. The cytokinin amounts in cells E and I of the zeatin group were smaller than those of other groups. We suggest that the concentration of cytokinins in tissue capable of generative development in winter wheat should be on a level that occurred in inflorescence cell lines, in comparison to immature embryo cell lines. These results indicate that the effect of the developmental stage of ears of wheat on the capability to flower in winter wheat plants regenerated in in vitro culture may be induced by the hormone level.