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Causes of limitation of plant reproduction by pollen and resource availability
Kalousková, Petra ; Janovský, Zdeněk (advisor) ; Sklenář, Petr (referee)
Plant seed production depends on many factors: their life history, the environment they grow in, and other factors such as biotic interactions. However, the immediate cause of the reduction in seed production is the lack of partners or the lack of resources available for seed production. This bachelor thesis aims to summarize and analyze the mechanisms of action and the relative importance of individual causes of limitation of plant seed production. Most plants are pollen limited at least in some seasons or in some localities, in the rest of the situations are plants resource limited. Pollen limitation can be quantitative (low pollen deposition) or qualitative (low quality of pollen). Existing theoretical models of pollen and resource limitation compare use of resources either to attract pollinators (increased flower size, increased number of rewards) and increase the chances of encountering them (change of phenology or prolongation of flowering) or to produce seeds. Plants can sometimes be seemingly pollen limited, with the pollen supplementation increasing seed production at the cost of reducing reproductive effort in the upcoming years. However, the most significant feature of pollination, which is often reflected in the alternation of reduced seed production due to insufficient pollen...
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Mode of reproduction and reproductive assurance of diploid and polyploid hawkweeds (Hieracium s. str.)
Zdvořák, Pavel ; Mráz, Patrik (advisor) ; Krahulcová, Anna (referee)
The mode of reproduction can greatly influence the demography and the evolutionary success of the taxon. In the case of autonomous asexual formation seeds are apomictic taxa fully independent of pollinators and compatible partners. For sexual taxa with strict autoincompatibility it is the opposite, i.e. sexual taxa need pollinators and compatible partners for birth of offspring. Therefore, in marginal population and for more extreme situation with lower pollinating activity will have apomictic taxa a higher level of reproductive assurance than sexual taxa vascular plants. This hypothesis was tested in natural populations of apomictic and sexual taxa. In the diploma thesis we therefore investigate the method mode of reproduction and reproductive assurance of 52 taxa of the genus Hieracium s. str. (family Asteraceae) in Europe. Of these, 12 were diploid sexually diploid taxa and 42 polyploid apomictic reproductive taxa. From these taxa we harvested seeds from fully developed capitulum and we determined the potential (total number of seeds in the capitulum) and the realized (the percentage of well-developed seeds at the capitulum). The ploidy of the offspring (the embryos and the seedling) and method origins of seeds we examined using flow cytometry. The results show that the plants of diploid species...
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Stanovení produkce semen a jejich klíčivosti u vybraných plevelných druhů z čeledi Asteraceae
Pohanková, Marcela
The aim of this diploma thesis "The determination of the production of seeds and their germination for selected species from the weedy family Asteraceae" is to find out the production of seeds and their germination of two selected weedy species from the family Asteraceae, depending on the location. The following were selected: Creeping Thistle (Cirsium arvense) and Wormwood (Artemisia vulgaris). Seed collection was done at seven locations with different habitat conditions (unmaintained hayfield, recultivated rubbish, garden, grass vegetation with grazing breeding of cattle, permanent grass vegetation, grasslands on arable land, forest land, other road, other area). After reviewing the available literature is discussed the biology and control of weeds and their significance. Furthermore is also characterized the family Asteraceae and selected representatives of this family . Subsequently is characterized the territory of interest. In addition is discussed the problematics of germination and seed production for Creeping Thistle (Cirsium arvense) and Wormwood (Artemisia vulgaris) depending on their habitats. The overall average HTS of Wormwood was 0.08 g, the average germination was 79%. The total average seed production of Creeping Thistle was 1 299 seeds, one plant had an average of 23 flowers and one flower had 51 seeds. Due to the very low number of sprouted seeds of this weed the germination parameter cannot be statistically evaluated.
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Influence of biotic and abiotic factors on population dynamics of a critically endangered species Spiranthes spiralis
IPSER, Zdeněk
A population of a critically endangered species Spiranthes spiralis was discovered in 1980 in the National Natural Monument Pastviště u Fínů near village Albrechtice, close to Sušice city. Since 1985 the number of flowering individuals in this population has been annually monitored. Since autumn 1998 all the specimen found there have been marked and biometrically measured. During these periods (12 or 26 years, respectively), large year-on-year fluctuations in the number of flowering plants and in the survival of the individual rosettes have been recorded. The main aim of my work was to assess the effect of weather conditions (temperature, precipitation, the number of days of snow) on the population dynamics and on the fitness of plants (leaf area, probability of flowering and probability of death). The year-round lower temperature and the wet end of autumn during the previous year (t-1) together with the wet spring of the following year (t) had a positive effect on the leaf area during the period of maximal rosette growth (end May in the year t). The probability of flowering was positively affected by the lower temperatures in May and June in the previous year (t-1) and in August just before flowering (year t). The probability of death (in the year t) was increased when the March precipitation (in t) and October temperatures (in t-1) were low. The average number of seeds in the capsule was 1528 ? 885 (s.d.). The number of flowers was positively correlated with the number of mature capsules. However, it did not affect the ratio of mature capsules. Capsules developed on average from 44% ? 24.6 % (s.d.) of the flowers. The average life time of individual plant cohorts was 4.7 years. The number of rosettes per each position was variable from 1 to 7 rosettes (73.2% positions had only 1 rosette). The annual life cycle of the underground organs is described at the end of the thesis.
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