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Strukturně funkční charakteristika průduchů jmelí bílého (Viscum album L.) a jeho hostitele lípy (Tilia sp.)
Bělíček, Dominik
This thesis deals with a comparison of the morphology of the stomata of the hemiparasite European mistletoe (Viscum album L.) and its host lime tree (Tilia sp.) in the context of physiological parameters such as water potential, stomatal conductance, and photosynthesis, in order to understand the relationship between the two species. The research was carried out at the Ústřední hřbitov in Brno. Here, 10 infested and 10 uninfested lime trees were selected. During the summer of 2022, varnish impressions were taken from the leaves of lime and mistletoe trees and then all physiological parameters were measured. It was found that mistletoe infestation had almost no significant effect on both the morphology and physiology of lime tree leaves. Furthermore, it was shown that mistletoe has more smaller stomata than linden. It has been shown that although mistletoe has a higher stomatal conductance, the photosynthetic rate is the same for both species, thus the water use efficiency of mistletoe is much lower. It was confirmed that mistletoe, as a hemiparasite, has a much lower water potential than the host. Although this information helps to understand this interrelationship, it also results in further uncertainties worth to investigate in future.
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Reakce sazenic břízy bělokoré (Betula pendula Roth.) na stres suchem
Orlovský, Vít
Climate change, with its accelerating intensity, is the primary factor to which forest and urban stands need to respond. Particularly more frequently, recurrent periods of drought, coupled with rising average annual temperatures, mainly in urban development, represent a significant plant stressor. As silver birch (Betula Pendula Roth) is a frequently used tree in urban plantings, the aim of this work was to assess the physiological response of silver birch seedlings after the completed leaf development to stress by drought. Evaluation of the response of the seedlings to stress confirmed the assumption that water potential decreases as the drought increases. Due to the stress of the drought, we saw an 86% decrease in water potential measured at noon compared to the beginning of the experiment. From the results of a 17-day experiment, we found that stress from drought caused a 96% decrease in the rate of photosynthesis and stomatal conductance. So birch seedlings reacted very sensitively to drought stress by trying to avoid reducing water potential. When comparing the variability of the responses of individual seedlings, the physiological parameters showed a marked difference in their response to stress by drought. For example, for rate of photosynthesis, the coefficient of variation for stressed seedlings reached 97% at the end of the experiment. The PRI reflectance index, which indirectly characterises the carotenoid content, showed a coefficient of variation of even 306%. All this information provides us with clear evidence of the ability of individual birch seedlings to react to drought stress in a different way. Based on our measurements and subsequent results, we can conclude that the variability of silver birch seed material is able to respond to the demands implied by the projected climate change.
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Vplyv veku na prieduchovú vodivosť a fotosyntézu dubu letného
Beňová, Eva
Increasing age brings along lowering of the tree vitality. Ecophysiological parameters as photosynthesis and its dependence on the concentration of CO2 (A-Ci curves) and light, chlorophyll fluorescence, stomatal conductance and water potential provide information on the physiological vitality of plants. These methods were used to assess the effect of age on the photosynthesis of pedunculate oak (Quercus robur). Two groups of trees were compared, the first group was over 600 years old while the second was less than 30 years old. Gas exchange measurements indicated lower light-saturated photosynthesis of old trees. Using A-Ci curves helped to estimate biochemical limitations of photosynthesis such as Vcmax, Jmax a Rd (maximum rate of carbon carboxylation, maximum electron transport speed and day respiration; respectively), which were similar for both groups of the trees. Chlorophyll fluorescence measurements enabled to estimate dark adapted (Fv/Fm) and light-adapted fluorescence (Fvˈ/Fmˈ). There were no differences between old and young trees in the parameters of chlorophyll fluorescence. However, the stomatal conductance was lower in old than in young trees under unlimited soil water availability. Resulting intercellular concentration of CO2 was lower in old trees, which indicated a lower concentration of CO2 at the sites of carboxylation and lower carbon assimilation rate. On the other hand, higher values of water potential of old trees in the mild drought in summer indicated their better access to soil water. Therefore, maximal stomatal conductance was similar in both groups of trees upon mild drought. Minimum stomatal conductance was higher in old trees. The results suggest that one of the reasons for the lowering of the vitality of old trees is their inability to regulate stomatal conductance, and to optimize carbon assimilation-water loss balance.
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Regulation of stomatal development by environmental conditions and physiological processes in the leaf
VRÁBLOVÁ, Martina
Stomatal development and its regulation by environmental conditions (light, CO2 concentration) and physiological processes in the leaf of higher plants were investigated. The study was based on the assumptions that stomatal development should be regulated by signals coming from both external environment and leaf interior, and that the signal should be transduced from cotyledons to leaves. Transgenerational effect in stomatal development was also studied. Molecular and physiological approaches were applied to reveal the relationship between leaf environment, stomatal development, stomatal function and leaf physiology.
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Vybrané ekofyziologické parametry stromů použitých při rekultivacích degradovaných půd v Etiopii
Velanová, Jana
Ecophysiological parameters, such as chlorophyll fluorescence and stomatal conductance (gs), provide a quantitative information on the effect of the stress factors on the plant physiological processes. Here we use gs and chlorophyll fluorescence as a proxy to assess the physiological vitality of 18 tree species used for the restoration of degraded land in Ethiopia. As for the fluorescence, we utilized parameters of yield upon full sunlight (QY) and ratio of variable to maximum fluorescence in darkness (Fv/Fm). Highest levels of gs and fluorescence were found in Sesbania bispinosa a Acacia saligna. These species were considered as least affected by the stress factors. The lowest levels of the above mentioned parameters were found at Podocarpus falcatus. Using these parameters we assessed actual physiological vitality of the trees. Other factors, considered before the use of these species were the invasiveness, wood properties and amelioration function. Suitable native species for the restorations may be Sesbania bispinosa and Acacia tortilis.
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Effect of light quality on diffusion limitations of photosynthesis
NEUWIRTHOVÁ, Jitka
Mesophyll conductance to CO2 transport is one of crucial components of diffusionall limitations of photosynthesis and is characterized by CO2 flux from sub-stomatal cavity to chloroplast stroma. Using Gas-exchange measurements A/Ci curves were analysed and by instantaneous carbon isotope discrimination mesophyll conductance was estimated. Measurements were conducted by sunflower irradiated with different light quality (blue, red and green component of photosynthetic active radiation).
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