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The relationship between ultrastructural changes in the anthers caused by cold pretreatment and the haploid induction capacity of different maize genotypes was investigated. The degeneration of the tapetal cells appears to be genotype-dependent, but the extent of the degeneration is not correlated with the androgenetic ability of the given genotype. Based on the stainability of the cytoplasm, two microspore types were found. The results suggest that the “dense” microspores take part in pollen embryogenesis.

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Colchicine is a plant alkaloid, known for thousands of years and currently used widely for the doubling of the genome in plant and animal cells due to its antimitotic effect. The aim of the present experiments was to develop stable autodiploid pollen grains in vitro in diploid lines of rye (Secale cereale L.) and barley (Hordeum vulgare L.) and to use these in intra- and interspecific crosses. Spikelet cultures of one rye and one barley variety were subjected to colchicine treatment in different stages of development and under differing in vitro conditions. Exposure to colchicine led to a drastic reduction both in the number of fertile pollen grains and in the percentage seed-setting, which was only observed in cultures inoculated in the early binuclear microspore stage. On medium containing colchicine the seed-setting percentage was 1.6% for barley and 0.1% for rye. Flow cytometry and root tip analysis revealed that all the progeny barley plants were diploid, while in the case of rye one was tetraploid, indicating that the egg cell may also be diploidised by colchicine treatment.

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Magyar Terminológia
Authors:
Eszter B. Papp
and
Barnabás Novák
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Abstract

Decentralized wastewater systems treat, dispose and reuse the wastewater in the vicinity of source, reducing the sewage transportation cost to minimal. As an alternative to centralized systems it can function as a satellite system or an individual wastewater treatment unit. Design an onsite facility applies the same sizing procedure compared the conventional large scale systems, whereas the input flow data and its variability, the model parameters could differ. In this study a small size treatment unit was designed by biokinetic modeling, where the model parameters were estimated using analytical methods. As a result of the calculation the biomass build-up and the quality of the treated effluent was predicted and the operation parameters were determined in summer and winter operation.

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Drought stress frequently occurs in the reproductive stage of wheat, causing significant yield loss. To study the developmental stage dependency of the effect of drought stress on photosynthesis, plants of the drought-tolerant Plainsman V and sensitive Cappelle Desprez winter wheat varieties were grown in phytotron chambers and subjected to water withholding during three phenophases of reproductive development: meiosis, anthesis and early seed development (ESD).Stomatal conductance (gs) and net photosynthesis (Anet) showed similar characteristics. Meiotic-stage drought only decreased the values of Cappelle Desprez significantly. Stressed Plainsman V showed a significantly smaller reduction and better regeneration for these parameters at anthesis. The decreases in gs and Anet were similar in both varieties when drought was applied during ESD. Studies on the intercellular CO2 concentration (Ci) inflexion point implied that metabolic impairment was less typical of stressed Plainsman V than of Cappelle Desprez at meiosis and anthesis. The quantum efficiency of PSII (ΦPSII) did not decline in either genotype during meiotic-stage drought. Stressed Plainsman V showed significantly higher ΦPSII values compared to Cappelle Desprez at anthesis. During ESD, the values for stressed plants of both genotypes decreased to a similar extent.The results indicate that the effect of drought stress on photosynthesis shows developmental stage dependency during the reproductive life cycle of wheat.

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A number of sporophytically induced microspores and embryo-like structures (ELS) were obtained from isolated microspore cultures of durum wheat ( Triticum turgidum L. cv. Martondur 1). Various pre-treatments were screened, involving spike treatment at 4°C for 2, 7 or 14 days; anther treatment in 0.4 M mannitol containing macroelements at 33°C for 3 days, and various combinations of these. The frequency of embryogenic (star-like) microspores and the number of ELS showed a very high positive correlation in the cultures. Starvation at high temperature was necessary to achieve a reasonable frequency of microspore embryogenesis. The best results were achieved when starvation at high temperature was combined with no or short (2-day) cold treatment (212±77 and 203±34 ELS/100 anthers, respectively). However, the ELS failed to regenerate; only a few of them produced poorly-developed albino shoots. The present work could be a promising starting point for the production of doubled haploid durum wheat plants in Hungary via isolated microspore culture.

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In the present work the effect of microalgal and cyanobacterial biomass on anther cultures of wheat (Triticum aestivum L.) was studied. Investigations were made on the influence of media supplemented with a biomass of four terrestrial and fresh-water microalgal and cyanobacterial strains (1-2 g l-1) on the androgenic response, frequency of microspore-derived embryo-like structures, and their regeneration capacity in anther cultures of wheat. The addition of 1 g L-1 of cyanobacterium biomass MACC 643 to the induction and regeneration media significantly improved the androgenic response by 50% in the genotype Mv Pálma, and reduced the requirement for the synthetic auxin 2,4-D.

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The chilling tolerance of doubled haploid (DH) maize plants selected and regenerated from microspores exposed to prooxidants, paraquat or tert-butyl hydroperoxide was determined by monitoring cold-induced changes in the photosynthetic electron transport, CO2 assimilation processes and chlorophyll breakdown in young leaves after cold treatment (8°C for 5 days). The results were compared to those of the non-selected DH line and the original hybrid plants. Chilling stress caused a great reduction in the Fv/Fm, qP and ΔF/Fm’ fluorescence parameters, related to the photosynthetic electron transport processes, and in carbon assimilation, and resulted in chlorophyll breakdown. These changes were less extensive in the selected DH plants, which showed elevated antioxidant capacity both at ambient and at low temperature. Among the antioxidant enzymes tested, the activity of GR and GST was induced by chilling stress to the greatest extent. Correlations between cold-induced changes in the photosynthetic apparatus and the antioxidant capacity of the plants suggested that the better protection against oxidative stress induced by the elevated antioxidant capacity of the plants contributed to protecting the photosynthetic apparatus from cold.

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The aim of the present study was to examine whether the induction of maize microspore embryogenesis could be triggered by the application of biogenic alcohols, as was reported earlier in wheat. A single cross hybrid (A 18) raised in the phytotron was used as anther donor for shed microspore cultures after cold pretreatment. At the onset of culturing, anthers in liquid YP medium were treated with 0.2 or 0.4% n-butanol or with 2 mM aminoethanol (2-AE) for 6 or 18 hours.The treatments caused a drastic (approx. 50%) decrease in the viability of the microspores. After a few days of culture in medium containing neither n-butanol nor 2-AE, 9-13% of the microspores remained alive and capable of switching to the sporophytic pathway of development.Treatment with 0.2% n-butanol for 6 h considerably increased the frequency of symmetric nuclear divisions (more than 3×) and of induced microspores (2×). The embryo yield was also elevated by 10%. The results showed that n-butanol could be used to improve the androgenic response and microspore embryogenesis in maize, but not as efficiently as in wheat. Further examination will be required to find the reasons for the different behaviour of microspores of the two species.

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Sexual reproduction plays an essential role in the propagation of Angiosperms. Fertilisation takes place in the embryo sac, which is usually deeply encased in the sporophytic tissues of the ovule. In contrast to animals and primitive plants, the mechanism of egg cell activation in flowering plants has not been discovered fully because of the inaccessibility and complexity of the process of double fertilisation. However, recent advances in plant cell and molecular biology have brought new, powerful technologies to investigate and micromanipulate the reproductive cells of flowering plants including cereal crops. An experimental approach based on various micromanipulation techniques involving in vitro fertilisation (IVF) and microinjection procedures is now available in more and more laboratories. Despite some limitations this offers new possibilities to study cellular and subcellular events preceding or occurring during or after egg cell activation and early embryonic development. Recent achievements in the field of wheat egg cell micromanipulation are presented in this paper.

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