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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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The phenomenon of Foliar Water Uptake - mechanisms and consequences with a focus on temerate plant species
Oramová, Viktorie ; Lhotáková, Zuzana (advisor) ; Ponert, Jan (referee)
The ability of plants to absorb water through leaves has been a matter of the sientific discussion for a long time. Among the epiphytic species (tilandsies for example), reduced root system and foliar water uptake (FWU) is considered an adaptation for life in soil-less environment, and FWU is a necesssity. It was surprising, that the same ability has been discovered in plant species with normally developed root system. Over the time, new pieces of evidence about FWU in broad range of plant species has been published and FWU is getting universal for all plants, across the taxonomic groups or biomes, including temperate zone. The systematic focus on FWU and continuity of its research is lacking and therefore the knowledge about FWU is still only partial. This bachelor's thesis is focused on mechanisms of FWU and the leaf structures that may mediate it. The ability of water to pervade cuticle through aquatic pores is discussed, together with the possibility of water absorption by stomata, trichomes, hydathodes or epiphylic organisms. Another discussed topic is the use of this water by plant - improving of the water regime, refilling of the embolized xylem vessels, possible exudation by roots etc. The matter of FWU has other consequences on the ecosystem level, like in water cycle or the plant's...
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