Changes of paramagnetic species in cereal grains upon short-term ozone action as a marker of oxidative stress tolerance.

The increase of the concentration of ozone in the atmosphere, being the direct source of reactive oxygen species, results in the yield loss of agronomic crops. On the other hand, ozone is also used as a protector against microorganisms, living in plants and present in materials obtained from them, dangerous for human and animal health. In this work it has been studied if ozone in doses similar to those used for removal of microorganisms can have significant influence on the generation of stable organic radicals and changes in the character of transition metal ions and in the antioxidative biochemical parameters of cereal grains.

Auxin and chloroplast movements.

Auxin is involved in a wide spectrum of physiological processes in plants, including responses controlled by the blue light photoreceptors phototropins: phototropic bending and stomatal movement. However, the role of auxin in phototropin-mediated chloroplast movements has never been studied. To address this question we searched for potential interactions between auxin and the chloroplast movement signaling pathway using different experimental approaches and two model plants, Arabidopsis thaliana and Nicotiana tabacum.

Role of phytochromes A and B in the regulation of cell death and acclimatory responses to UV stress in Arabidopsis thaliana.

Plants coordinate their responses to various biotic and abiotic stresses in order to optimize their developmental and acclimatory programmes. The ultimate response to an excessive amount of stress is local induction of cell death mechanisms. The death of certain cells can help to maintain tissue homeostasis and enable nutrient remobilization, thus increasing the survival chances of the whole organism in unfavourable environmental conditions.

Free and Cell Wall-Bound Polyamines under Long-Term Water Stress Applied at Different Growth Stages of ×Triticosecale Wittm.

Background: Long-stemmed and semi-dwarf cultivars of triticale were exposed to water stress at tillering, heading and anthesis stage. Quantitative determination of free and cell wall-bound polyamines, i.e.

Stable radicals and biochemical compounds in embryos and endosperm of wheat grains differentiating sensitive and tolerant genotypes--EPR and Raman studies.

The aim of this study was to uncover the specific species in grains that might differentiate the wheat genotypes according to their tolerance to oxidative stress. Measurements by EPR and Raman spectroscopy techniques were used to examine whole grains and their parts (embryo, endosperm, seed coat) originating from four wheat genotypes with differing tolerance to drought stress. Raman spectra showed that, in spite of the similar amounts of proteins in whole grains from tolerant and sensitive genotypes, in tolerant ones they were accumulated mainly in embryos.

Current insights into hormonal regulation of microspore embryogenesis.

Plant growth regulator (PGR) crosstalk and interaction with the plant's genotype and environmental factors play a crucial role in microspore embryogenesis (ME), controlling microspore-derived embryo differentiation and development as well as haploid/doubled haploid plant regeneration. The complexity of the PGR network which could exist at the level of biosynthesis, distribution, gene expression or signaling pathways, renders the creation of an integrated model of ME-control crosstalk impossible at present. However, the analysis of the published data together with the results received recently with the use of modern analytical techniques brings new insights into hormonal regulation of this process.

High expression of SOMATIC EMBRYOGENESIS RECEPTOR-LIKE KINASE coincides with initiation of various developmental pathways in in vitro culture of Trifolium nigrescens.

The aim of this study was to identify and examine the expression pattern of the ortholog of SOMATIC EMBRYOGENESIS RECEPTOR-LIKE KINASE gene from Trifolium nigrescens (TnSERK) in embryogenic and non-regenerative cultures of immature cotyledonary-stage zygotic embryos (CsZEs). In the presence of 1-naphthaleneacetic acid and N(6)-[2-isopentenyl]-adenine, the CsZE regenerated embryoids directly and in a lengthy culture produced callus which was embryogenic or remained non-regenerative. As revealed by semi-quantitative reverse transcription polymerase chain reaction (RT-PCR), the TnSERK was expressed in both embryogenic and non-regenerative cultures, but the expression level was significantly higher in embryogenic ones.

Disturbances in production of progesterone and their implications in plant studies.

Progesterone is a mammalian hormone that has also been discovered in plants but its physiological function in plants is not explained. Experiments using inhibitors of progesterone synthesis and binding would be useful in studies on the significance of this compound in plants. Until now, trilostane and mifepristone have been used in medical sciences as progesterone biosynthesis and binding inhibitors, respectively.

Hormonal requirements for effective induction of microspore embryogenesis in triticale (× Triticosecale Wittm.) anther cultures.

Effective microspore embryogenesis in triticale is determined by a specific hormonal homeostasis: low value of IAA/cytokinins, IAA/ABA and cytokinins/ABA ratios as well as proper endogenous/exogenous auxin balance, which favours androgenic structure formation and green plant regeneration ability. The concentration of plant growth regulators (PGRs): auxins (Auxs), cytokinins (CKs) and abscisic acid (ABA) was measured in anthers of eight DH lines of triticale (× Triticosecale Wittm.), and associated with microspore embryogenesis (ME) responsiveness.

Comparison of a compatible and an incompatible pepper-tobamovirus interaction by biochemical and non-invasive techniques: chlorophyll a fluorescence, isothermal calorimetry and FT-Raman spectroscopy.

Leaves of a pepper cultivar harboring the L(3) resistance gene were inoculated with Obuda pepper virus (ObPV), which led to the appearance of hypersensitive necrotic lesions approx. 72 h post-inoculation (hpi) (incompatible interaction), or with Pepper mild mottle virus (PMMoV) that caused no visible symptoms on the inoculated leaves (compatible interaction). ObPV inoculation of leaves resulted in ion leakage already 18 hpi, up-regulation of a pepper carotenoid cleavage dioxygenase (CCD) gene from 24 hpi, heat emission and declining chlorophyll a content from 48 hpi, and partial desiccation from 72 hpi.

The localization of NADPH oxidase and reactive oxygen species in in vitro-cultured Mesembryanthemum crystallinum L. hypocotyls discloses their differing roles in rhizogenesis.

This work demonstrated how reactive oxygen species (ROS) are involved in the regulation of rhizogenesis from hypocotyls of Mesembryanthemum crystallinum L. cultured on a medium containing 1-naphthaleneacetic acid (NAA). The increase of NADPH oxidase activity was correlated with an increase of hydrogen peroxide (H2O2) content and induction of mitotic activity in vascular cylinder cells, leading to root formation from cultured hypocotyls.

PHYTOALEXIN DEFICIENT 4 affects reactive oxygen species metabolism, cell wall and wood properties in hybrid aspen (Populus tremula L. × tremuloides).

The phytoalexin deficient 4 (PAD4) gene in Arabidopsis thaliana (AtPAD4) is involved in the regulation of plant--pathogen interactions. The role of PAD4 in woody plants is not known; therefore, we characterized its function in hybrid aspen and its role in reactive oxygen species (ROS)-dependent signalling and wood development. Three independent transgenic lines with different suppression levels of poplar PAD expression were generated.

The influence of heat stress on auxin distribution in transgenic B. napus microspores and microspore-derived embryos.

Plant embryogenesis is regulated by differential distribution of the plant hormone auxin. However, the cells establishing these gradients during microspore embryogenesis remain to be identified. For the first time, we describe, using the DR5 or DR5rev reporter gene systems, the GFP- and GUS-based auxin biosensors to monitor auxin during Brassica napus androgenesis at cellular resolution in the initial stages.

A dissection of the effects of ethylene, H2O2 and high irradiance on antioxidants and several genes associated with stress and senescence in tobacco leaves.

Ethylene and hydrogen peroxide are involved in the modulation of stress responses in plants, but their interrelation is not well understood. This work was designed to find differences between the actions of ethylene and H2O2 on antioxidants and senescence markers. Leaves of Nicotiana tabacum were sprayed with H2O2 or with ethephon (precursor of ethylene).

Characterization of polarity development through 2- and 3-D imaging during the initial phase of microspore embryogenesis in Brassica napus L.

Isolated microspores of B. napus in culture change their developmental pathway from gametophytic to sporophytic and form embryo-like structures (ELS) upon prolonged heat shock treatment (5 days at 32 °C). ELS express polarity during the initial days of endosporic development.

An increase in the content of cell wall-bound phenolics correlates with the productivity of triticale under soil drought.

The objective of this study was to investigate whether the content of cell wall-bound phenolics can simultaneously influence both the productivity and the water status of triticale under soil drought conditions. Two parallel treatments were carried out. The T1 treatment involved plants being subjected to soil drought twice, during the tillering phase and then during the flowering phase.

Early stage de-etiolation increases the ferulic acid content in winter triticale seedlings under full sunlight conditions.

In the presented work an attempt has been made to estimate the phenolics content and its implication for the protection of the photosynthetic apparatus in course of a plant's de-etiolation. The experiments were carried out on two genotypes of winter triticale varying in their resistance to drought. The activity of the photosynthetic apparatus was monitored by taking measurements of chlorophyll fluorescence and chlorophyll/carotenoids content.

Possible contribution of cell-wall-bound ferulic acid in drought resistance and recovery in triticale seedlings.

Studies were undertaken to estimate whether the presence of free and cell-wall-bound ferulic acid in leaf tissues can support drought resistance and its recovery under rehydration. An experiment was carried out on two genotypes of winter triticale: Lamberto and Ticino, at the propagation phase. Lamberto exhibited high content of ferulic acid bound with carbohydrates of the cell-wall under drought and rehydration.

Physiological and biochemical parameters for identification of QTLs controlling the winter triticale drought tolerance at the seedling stage.

The genetic map of the triticale is created on the basis of double-haploid (DH) lines, derived from F1 hybrids of a cross between the parental line Saka3006 and Modus. In order to localise drought resistance genes, it is necessary to find a phenotype feature which clearly differentiates between parental lines under drought stress conditions. With the future in mind, the aim of the presented studies was to analyse differences in the response to drought stress, between Saka3006 and Modus.

Salt tolerance of barley induced by the root endophyte Piriformospora indica is associated with a strong increase in antioxidants.

The root endophytic basidiomycete Piriformospora indica has been shown to increase resistance against biotic stress and tolerance to abiotic stress in many plants. Biochemical mechanisms underlying P. indica-mediated salt tolerance were studied in barley (Hordeum vulgare) with special focus on antioxidants.

Physiological and biochemical tools useful in drought-tolerance detection in genotypes of winter triticale: accumulation of ferulic acid correlates with drought tolerance.

Background And Aims: The objectives of this study were to investigate whether a classification of triticale genotypes into drought-tolerant and drought-sensitive types based on field performance trials correlates with a classification based on measurements of some physiological and biochemical parameters in greenhouse conditions. In addition, an examination was carried out of whether ferulic acid, as the main origin of the blue fluorescence produced, contributes to drought tolerance.

Methods: Ten winter triticale genotypes were examined, five known to be drought tolerant and five drought sensitive.