Equisetum arvense is an evolutionary old species that is common as a perennial weed in Europe, North America and Australia. It reproduces vegetatively via rhizomes and tubers and due to this it spreads efficiently below ground after initial establishment. The aim of this study was to increase the knowledge of performance during early growth of the species. This included differences between clones along a gradient throughout Sweden, development of tubers and rhizomes, local adaptation and the overall variation within the species. Rhizomes of E. arvense were collected from three different places in each of four regions, up to 1000 km apart, in Sweden. Clones from the twelve places were planted in spring for a common garden study. During summer the plants were watered when needed and during late summer the plants were harvested every second week until late autumn. Data recorded were tuber and rhizome biomass, aboveground biomass, number of tubers and three different tuber characteristics. The results showed clone specific phenotypes, but no gradient response or adaptation to regions, e.g. the clone with the highest and the clone with the lowest tuber biomass in relation to the rhizome biomass were from the same region. During early growth, the plants developed continuously with rapid increase of belowground biomass after development of aboveground photosynthetic parts. Tuber productions differed a lot between clones. The relationship between tubers and rhizomes may affect the clone’s possibility to be competitive in different environments. Management advice may need to be based on clone specific knowledge.

Rhizophytic algae are large, abundant primary producers throughout tropical and subtropical areas worldwide where they grow as an understory in seagrass beds, as well as form mixed or monospecific beds of exclusively rhizophytic algal species. In this dissertation, "rhizophytic algae" refers to coenocytic green algae (Chlorophyta) in the order Bryopsidales that use a net of rhizoids to anchor in unconsolidated sediments. In the development of seagrass beds, rhizophytic algae colonize bare patches and are thought to facilitate seagrass colonization by stabilizing sediments and providing organic matter. However, despite their prominence little is known about many aspects of the ecology of rhizophytic algae. Detailed information on the abundance and biomass of rhizophytic algae at the species level is scarce and the belowground components are seldom quantified. Moreover, rhizophytic algal communities located along the central west coast of Florida have received very little study. At three shallow coastal sites in the Lower Florida Keys and one on the central west coast of Florida, I measured the abundance, biomass, organic content, and morphometric features of the above- and belowground portions of all rhizophytic algal species present along transects in seagrass-algal bed habitat. Relatively diverse assemblages of these algae were present both in areas with and without a seagrass canopy, though dense (greater than or equal to 50%) seagrass cover correlated with decreased algal richness. Rhizophytic algal densities at Keys sites ranged from 68 - 143 thalli m-2 with total dry weights of 76.4 - 226.7 g m-2 with only calcified species present. The west coast of Florida site had the highest aboveground organic biomass (180 g m-2), the highest abundance of rhizophytic algae (365 thalli m-2), and abundant uncalcifed algae of the genus Caulerpa. Morphometric characteristics varied within a species among sites and may reflect differences in abiotic variables such as sediment grain size. The anchoring structures of these algae, made up of fine rhizoids and attached sediment, occupied up to 5.3% of the total volume of the top 5 cm of substrate. My results indicate that across rhizophytic algal species, even within a genus, the production of belowground structure and potential influence on ecosystem function is highly variable and not necessarily related to the aboveground biomass. These results provide new information on belowground structure provided by rhizophytic algal species and characterize the rhizophytic algal community on the central west coast of Florida. The role of rhizophytic algae in seagrass bed succession has been recognized, but little is known about the rate and species composition of colonization of recently created bare patches. In a series of field experiments at three sites on the central west coast of Florida, recruitment by rhizophytic algae into created cleared areas was rapid and dominated by two species of Penicillus and Udotea flabellum. In three weeks, rhizophytic algae were able to recruit, grow to their full height, and bind sufficient sediment to create full-sized holdfasts. Additional field experiments described here show thalli of all of the rhizophytic algal species tested (three species in three genera) were able to regenerate from holdfasts (with small stubs of stipe attached) in a matter of weeks. Overall, my results suggest that belowground structures play a key role in recolonization by, and recovery of, rhizophytic algae after disturbance and are likely important to the long-term persistence of these algal populations. Bryopsidalean algae often have high concentrations of defensive compounds inside their thalli and these terpenoid secondary metabolites possess anti-fouling capability in laboratory tests. Because fouling is ubiquitous in marine environments and epibonts have harmful effects on their hosts, researchers have proposed that rhizophytic algae use these compounds to prevent fouling. For this to be an effective strategy, the compounds must be presented to potential colonizers on the external aboveground surfaces. Thus, I examined the chemistry of rhizophytic algal surfaces using extractions that avoid mechanical damage. Secondary metabolites were not detected in the surface extracts of four species while these compounds were detected in the whole plant extracts. My results, coupled with previous studies on the degradation of these metabolites in seawater and the presence of fouled plants in the field, and suggest non-polar secondary metabolites are not deployed onto the surfaces of rhizophytic algae as a defense against fouling.

京都大学 / 新制・課程博士 / 博士(理学) / 甲第24455号 / 理博第4954号 / 新制||理||1707(附属図書館) / 京都大学大学院理学研究科生物科学専攻 / (主査)教授 中野 伸一, 教授 木庭 啓介, 教授 中務 真人 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM

Master of Science / Department of Biology / David C. Hartnett / Perennial grasses on tallgrass prairie primarily reproduce vegetatively via the belowground bud bank, yet the production, dynamics, and morphology of belowground buds is largely unexplored. Since the two main photosynthetic pathway guilds (C3 and C4) on tallgrass prairie vary in their aboveground phenology, their belowground phenology would also be expected to vary. Differences in bud production, development, and spatial arrangement result in different growth forms. Therefore, an extensive biweekly examination of a dominant tallgrass prairie C4 rhizomatous grass Andropogon gerardii and C3 caespitose grass Dichanthelium oligosanthes was conducted over an entire year. Andropogon gerardii and D. oligosanthes have multiple distinctive bud developmental stages. Andropogon gerardii was synchronous in its bud development and its bud bank was composed of multiple annual cohorts. The bud bank of D. oligosanthes was developmentally asynchronous and was comprised of a single bud cohort since its bud bank underwent a complete turnover in early summer. The different roles of buds in the life history of each species reflected their differences in bud longevity, quality, and dormancy. In D. oligosanthes, belowground buds enabled plant survival over the C3 summer dormant period whereas juvenile tillers overwintered during the longer winter dormant period. In contrast, A. gerardii survived its single, winter dormant period as dormant buds. The higher-order bud production observed in D. oligosanthes multiplied its tiller production potential and, along with its shortened internodes, contributed to its caespitose growth form. The rhizomatous growth form of A. gerardii resulted from its lack of higher-order bud production and its elongated internodes. Differences in production of buds per vegetative and flowering tiller were quantified in A. gerardii. Flowering tillers of A. gerardii produced larger numbers of buds per tiller and transitioned a larger proportion of their buds to tillers than did vegetative tillers. Therefore, no tradeoff between sexual and vegetative reproduction was evident. Developmental constraints likely prevented such a tradeoff. Bud bank dynamics offer insight into the control of grass population dynamics, production, and ultimately aboveground net primary production (ANPP) and will be useful in understanding the underlying mechanisms by which management practices and environmental change can alter perennial grasslands.

Doctor of Philosophy / Department of Biology / David C. Hartnett / Perennial grass populations propagate vegetatively via the belowground bud bank. Climate, photosynthetic pathway, and growth form impact bud production, longevity, and dormancy; leading to alterations in bud bank and tiller dynamics. Previous research in mesic C₄-dominated tallgrass prairie revealed that a C₄ grass had greater bud longevity and differing bud bank dynamics than a C₃ species. This study examined the bud bank dynamics of rhizomatous and caespitose grasses in a more arid C₃ dominated prairie to gain insights into how bud banks differ among grass species, growth forms, and environments, and the relationship between bud bank characteristics and grass architecture and growth patterns. The bud bank and tiller dynamics of four perennial grasses in the C₃-dominated northern mixed grass prairie were examined over 15 months. The C₃ caespitose and rhizomatous grasses produced similar numbers of buds per tiller and their bud longevity was [greater than or equal to] 2 years. Tiller longevity drove the turnover within the bud bank of the dominant C₃ caespitose grasses Hesperostipa comata and Nassella viridula. Their polycyclic tillers (tillers that lived for more than one year) created multi-aged bud banks. The rhizomatous C₃ grass Pascopyrum smithii also had a multi-aged bud bank because buds were able to live longer than its annual tillers. Differences between caespitose and rhizomatous C₃ grass bud banks were driven by differences in tiller and rhizome production and spatial distribution. Responses to water availability fluctuations are likely buffered by the maintenance of polycyclic tillers in the caespitose grasses and flexible timing of annual tiller recruitment in the rhizomatous grass. The C₄ rhizomatous grass Andropogon gerardii had similar phenology to populations in its tallgrass prairie range center. Despite declines in bud production per tiller and lowered flowering probability in mixed-grass prairie, A. gerardii maintained a multi-aged bud bank and a positive population growth rate via vegetative reproduction at both the center and edge of its range. Bud bank dynamics of different growth forms and photosynthetic pathways, as they offer insight into the control of grass population dynamics and production, will enhance understanding of the mechanisms by which management practices and environmental change can alter perennial grasslands.

The scope of this thesis was to identify, describe and quantify important life-history traits for the pseudoannual aquatic plant Ranunculus lingua in different ecological settings, by comparing populations from geographically marginal vs. central habitats. Results from a four-year field study showed that abiotic factors (water-level fluctuations and associated processes) tended to have a greater influence in marginal populations, whereas biotic factors (competition, insect grazing and fungal infections) dominated in central populations. This was reflected in different depth distribution of ramet numbers and ramet sizes between the areas, and In different dynamic patterns, with a higher flux of ramets in marginal populations. In a reciprocal transplant experiment, marginal ramets produced more but smaller rhizomes, whereas central ramets produced Individually larger but fewer rhizomes, irrespective of transplant site. A possible selection for genotypes producing large rhizomes in the central habitat was supported by the fact that initially smaller ramets were more likely to be diseased by the fungal pathogen Peronospora gigantea and damaged by insect grazing. In the marginal population, where density-independent mortality factors tend to dominate, a high reproductive output, expressed in production of high numbers of rhizomes, was suggested to be a favoured life-history trait. In a glasshouse experiment, ramets from marginal and central populations were grown in low and high densities and under three contrasting nutrient levels. The allocation to sexual structures was generally very low, and did not incur any costs in terms of reduced rhizome production. Rhizome production showed strong positive allometrical relationships to mother ramet size. Increasing mother ramet size resulted in a larger increase in rhizome numbers for the marginal than for the central population, whereas the increase in mean rhizome mass was more pronounced for the centred population. Both populations showed similar reductions in rhizome production in response to increased density and lowered nutrient levels, which could not be explained by size-dependent effects adone. The dispersal, dynamics and distribution of R. lingua were studied in a marginal river population in northern Sweden, where the only means of dispersal is by vegetative diaspores, i.e. floating rhizome fragments. Stranding occurred mainly in river curves and at obstacles, and the distribution of established stands was also highly correlated with these features. Relative changes in ramet numbers were correlated with water-level fluctuations during the present and previous growing seasons, with winter low-water, and with duration of spring-flood. The predictability of change was high within but low between stands. It was concluded that the patterns and mechanisms of dispersal are fundamental for local distribution patterns as well as variation in regional abundance in R. lingua / <p>Diss. (sammanfattning) Umeå : Umeå universitet, 1992, härtill 4 uppsatser</p> / digitalisering@umu