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Phototropic memory in early plant development
Šišková, Michaela ; Konrádová, Hana (advisor) ; Krtková, Jana (referee)
This thesis was inspired by controversial published results on the existence and reliability of a memory trace of the direction of the last illumination in young dicots. The theoretical part first covers phototropism, it briefly summarizes current knowledge about this growth movement, phototropins, and the mechanism of phototropic bending, including the role of auxin and its transporters. It also discusses the effect of previous light exposure on hypocotyl bending. Another section of the theoretical part is focused on the question of the existence of memory in plants. The experiments performed in the practical part are based on the assumption that plants are able to store a memory trace of previous light exposure. After the establishment of a system that made it possible to obtain a robust phototropic response to blue light, seedlings of the model plant Lepidium sativum were tested under different conditions to see if and how the direction of light affected the plants' response to subsequent phototropic stimulation. The results suggest that in at least one case, the final phototropic response could be interpreted as a formation of a specific memory trace in the tested plants. However, based on the results of this work, the existence of a memory trace of previous light exposure cannot be...
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3D rekonštrukcia povrchu buniek hypokotylov Arabidopsis thaliana so zmenenými hladinami cytokinínov
Hubinský, Marcel
Plants are multicellular organisms, which tightly control their growth and morphogene-sis to successfully accomplish the final reproductive individual plant. At the cellular level, plant development consists of two main processes, cell proliferation and cell ex-pansion. Differences in the timing, rate and spacing of these developmental processes determine the final size and structure of plants organs, such as hypocotyl. Cytokinins (CKs) play a key role during many aspects of plant development, including hypocotyl development. We confirmed the important role of CK during expansion phase of hypocotyl cells. Hypocotyls with increased levels of CK growing under low light conditions were formed by elongated epidermal cells whereas hypocotyls lacking CK produced smaller cells. Using advanced confocal microscopy methods and transgenic plants with GFP-labeled cortical microtubules (proCaMV35S::MBD-GFP) enabled to design recon-struction of hypocotyl surface with altered levels of CK. The final 3D model of hypocotyl epidermal cells shed a light on detail morphological changes upon CK alterations
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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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Transport 2,4 - dichlorfenoxyoctové kyseliny v explantátech okurky seté (Cucumis sativus L.)
Hajdamachová, Iva
For the experiment were used threecentimeters hypocotyl segments cucumbers sown (Cucumis sativus L.), cultured on MS medium and induction medium with added growth regulators. The aim was to demonstrate bazipetal transport 2,4- dichlorophenoxyacetic acid (2,4 - D ) in hypocotyls . Transport 2,4-D was detected by morphological evaluation of all variants of the experiment, by determining the weight of dry matter and distribution of 14C-activity after uptake 14C-2,4-D from the culture medium. 2,4-D induced callus in hypocotyls cultured on induction medium and subcultured in hypocotyls after 3 and 6 days on MS medium . The largest callus formed at the basal part of hypocotyls, which confirmed bazipetal transport 2,4-D. During cultivation hypocotyls were found bazipetal distribution of 14C-activity originating 14C-2,4-D. The hypocotyls cultured on MS medium was successfully formed roots on theirs basal parts, but for variants subcultured on MS medium for 3 days, the resulting larger roots.
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Adventitious sprouting of short-lived plants in natural populations
MALÍKOVÁ, Lenka
Disturbance is one of most important selective factor causing removal of plant biomass. Man-made habitats are characterized by strong and unpredictable disturbances, providing bare soil surface colonized by plants with short life cycle. Populations of the short-lived plants are, however, vulnerable to the strong disturbance removing all stem parts with reserve axillary meristems in the case it occurs before plant flowering and fruiting. Nevertheless, 2 % of annual and 14 % of biennial plants are able to overcome meristem limitation by adventititous sprouting from hypocotyle or/and roots. This thesis is composed of four original studies describing the occurrence of adventitious sprouting in natural populations of 22 monocarpic weeds of Central Europe and one species in Indonesia. The studied phenomenon was analyzed in relation to various environmental factors and plant traits in the field and in experimental conditions.
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