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Interakce teploty a hormonů v růstu Arabidopsis thaliana
Andrýsková, Kristýna
Abstract Due to global warming, plants are exposed to higher temperatures more often and for longer time periods. Exceeding the temperature optimum causes heat stress and affects plant growth and morphology. The most common plant reactions to high temperature are elongation of the hypocotyl, leaf hyponasty, or elongation of leaf petioles. All these morphological changes are collectively referred to as thermo-morphogenesis. The key modulator of this process is the transcription factor phy-tochrome-interacting factor PIF4. It is the main regulator of thermomorphogenesis through which the YUCCA8 gene is activated. YUCCA8 is a biosynthetic enzyme in auxin metabolism that induces auxin accumulation and activates cell elongation. The experimental part was focused on the influence of cytokinin hormones on the growth of the hypocotyl in Arabidopsis thaliana at standard (20 °C) and elevated (29 °C) temperatures. The increased temperature had a positive effect on the growth of the hypocotyl of control plants as well as transgenic lines with ectopic expression of the PIF4 gene. The effect of the application of 10µM trans-zeatin was temperature dependent. At standard temperature, cytokinins had a positive effect on the growth of the hypocotyl of control plants but did not have a significant effect in transgenic lines. However, transgenic lines had elongated hypocotyls compared to wild-type plants at standard temperature. Conversely, at a higher temperature, cytokinins only had an inhibitory effect. Automatic analysis of the abundance of the PIF4 pro-tein using GFP showed that its level within the hypocotyl is uneven with increasing abundance in the direction from the root to the cotyledons. Confocal microscopy confirmed that the inhibitory effect of cytokinins on hypocotyl elongation at higher temperatures is not due to a decrease in the PIF4 protein level.
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Mechanisms that control physiological seed dormancy
Řezková, Natálie ; Ponert, Jan (advisor) ; Vosolsobě, Stanislav (referee)
Physiological dormancy is an important developmental trait ensuring that seed does not germinate when the environmental factors are appropriate only temporary. The transition from seed dormancy to germination is regulated by a large number of factors and the phytohormone abscisic acid (ABA) plays a crucial role. Enhanced response to ABA and its biosynthesis is a key mechanism in dormancy induction and maintenance. ABA interacts antagonistically with gibberellins (GAs). Therefore GA biosynthesis and ABA catabolism are positive germination regulators. However, other phytohormones are also involved in the regulation of dormancy and germination. The most studied is ethylene which supports germination similarly to GA. Numerous factors affect dormancy at molecular level, namely chromatin remodeling, gene products that function only in dormancy regulation [e.g. DELAY OF GERMINATION 1 (DOG1)] or gene products that mediate seed response to environmental factors. The dormancy, its induction, depth and release, is driven not only by environmental conditions affecting mature seeds, but also by conditions acting during seed maturation in a maternal plant when the primary dormancy is induced. Requirements for dormancy release and germination induction may vary considerably between species. The physiological...
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Ovlivnění odpovědí rostlin k teplotnímu stresu modulací hladin cytokininů a giberelinů
Kharkevich, Kristina
Plants are sessile organisms which are very much affected by global climate change. In order to prevent themselves by overheating Arabidopsis plants induce growth to cool themselves more efficiently. Growth response to increased ambient temperature is modulated by different classes of hormones. Despite their importance in proliferation, effect of cytokinins under increased ambient temperature haven been studied in details so far. Experiments with transgenic plants expressing bacterial gene ipt and Hordeum vulgare gene HvCKX revealed that increased and also decreased levels of cytokinins affect morphometric parameters of Arabidopsis seedlings and plants. Experiments with mutant lines revealed that cytokinin-induced growth responses are independent of light signalling and response regulators controlling circadian rhythm. Combine experiments with pharmacological substance and genetic mutants show that cytokinin-induced growth responses under heat stress are independent of gibberellin signalling pathway. Formula clause:I herewith request that my Diploma thesis (Cytokinins and gibberellins induced changes in growth response to heat stress) is excluded from the open public access granted in accordance with the Section 47b of Act No. 111/1998 Coll., on Higher Education Institutions and the alterations and amendments thereto. This work contains sensitive data that are prepared for publishing in an impacted scientific journal. The restriction should last for at least 24 months.
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Interakce giberelinů a cytokininů v růstu klíčních rostlin Arabidopsis thaliana
Horáková, Adéla
Recently global warming and increasing environmental temperature are discussed very frequently. Ambient temperature is an important factor regulating plant growth and global changes in temperature could significantly affect the yield of the agriculture. Our previous work revealed the role of plant hormones cytokinins in response to temperature and showed cytokinins as negative regulators of the thermomorphogenesis. Since gibberellins are known as positive regulators of the thermomorphogenesis this work was focused on their interaction in response to temperature in Arabidopsis thaliana. Analysis of the morphology of plant seedlings showed that the effect of cytokinins dominates over gibberellins in response to high temperature and is detectable soon after high-temperature treatment. Analysis of gene expression showed that cytokinins induce expression of gibberellin biosynthesis enzyme GA20ox1 and decrease the expression of gibberellin degradation enzyme GA2ox6. On the other hand, cytokinins have an inhibitory effect on the expression of the master regulator of thermomorphogenesis PIF4. Analysis of transgenic line overexpressing PIF4 suggests that cytokinins could affect the thermomorphogenesis by regulation of the PIF4 expression but this process is not the key mechanism of the regulation of the response to high temperature.
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Mechanisms that control physiological seed dormancy
Řezková, Natálie ; Ponert, Jan (advisor) ; Vosolsobě, Stanislav (referee)
Physiological dormancy is an important developmental trait ensuring that seed does not germinate when the environmental factors are appropriate only temporary. The transition from seed dormancy to germination is regulated by a large number of factors and the phytohormone abscisic acid (ABA) plays a crucial role. Enhanced response to ABA and its biosynthesis is a key mechanism in dormancy induction and maintenance. ABA interacts antagonistically with gibberellins (GAs). Therefore GA biosynthesis and ABA catabolism are positive germination regulators. However, other phytohormones are also involved in the regulation of dormancy and germination. The most studied is ethylene which supports germination similarly to GA. Numerous factors affect dormancy at molecular level, namely chromatin remodeling, gene products that function only in dormancy regulation [e.g. DELAY OF GERMINATION 1 (DOG1)] or gene products that mediate seed response to environmental factors. The dormancy, its induction, depth and release, is driven not only by environmental conditions affecting mature seeds, but also by conditions acting during seed maturation in a maternal plant when the primary dormancy is induced. Requirements for dormancy release and germination induction may vary considerably between species. The physiological...
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Interakcia cytokinínov a giberelínov počas predlžovania hypokotylu v odpovedi na rôzne teplotné podmienky
Tarbajová, Vladimíra
This study observed the involvement of plant hormones, cytokinins during extension of the hypocotyl of Arabidopsis thaliana seedlings ecotype Col-0 in response to ambient temperature. It also observed possible coordination of phytohormones cytokinins with gibberellin pathway, using pentuple della mutant lines background ecotype Ler-0 exposing to elevated temperature. Attention was also paid to regulation of extension growth on the transcriptional level using single and multiple pif mutant lines on a background of the ecotype Col-0. The exogenous application of cytokinin (tZ) demonstrated that elevated levels of cytokinins stimulate the extension growth of the hypocotyl under conditions of optimum temperature (20 ° C). In contrast, the trans-zeatin treated wild type of Arabidopsis thaliana showed inhibition of growth of the hypocotyl under conditions of high ambient temperature (29 ° C). Using a gibberellins´ biosynthesis inhibitor, paclobutrazol, some modulation of hypocotyl elongation thru cytokinins was found in response to the optimal and increased ambient temperature.
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Využití regulátorů růstu v ječmeni jarním k omezení poléhání
Tvrdý, Hynek
This thesis deals with use of growth regulators to reduce lodging of spring barley (Hordeum vulgare L.). The field trial was conducted in corn production area on a clay-loamy glue fluvisol since 2012 to 2014. An effect of growth regulators was monitored on spring barley of the variety Bojos. Preparations Retacel extra R 68 (chlormequat chloride), Moddus (trinexapac-ethyl) and Cerone 480 SL (etephon) were chosen to crop regulation. The aim of the thesis was to carry intensive crop barley focused on correct application of growth regulators according to the cultivation methodologies. Growth regulators were used in various combinations with one another in three dose and dosage times. From this reason cob length, number of seeds per spike, grain yield and selected parameters of malting barley quality were monitored and evaluated. There was no negative effect of different combinations and does of growth regulators on production and quality of spring barley while the aim of crop shortening was achieved. In 2014 up to 20% of the effect of stalk length shortage was achieved. The greatest shortening was achieved on the stalks with higher dose of Cerone. In 2013 the yield increased of 1,95 t.ha-1 in variants with growth regulators.
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Vliv aplikace kyseliny giberelové na kvalitu plodů jabloní
Dostál, Pavel
This thesis is focused on monitoring the impact of the application of gibberellic acid contained in GIBB PLUS growth regulator applied to the shapes of slender spindle apple trees on fruit quality and the economic advantage of the variety 'Golden Delicious', the advantages and disadvantages of such applications compared to the control without treatment. Application and monitoring was carried out during the growing season in 2013 to nine-year apple trees in full fertility, stunted grown on M9 rootstocks growing in an orchard located in the northern part of the Western Carpathians in the so-called Ostrava basin in northern Moravia, near the town of Havirov. In the practical part the effect of an application on fruits, namely the occurrence of rust, starch content, soluble solids and titratable acids in the flesh of the fruit size parameters. The results were statistically processed. At the end of the economic evaluation was performed.
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