The period after the I Ind World War was characterized by growing interest in water plants. This review describes very briefly the development of these studies. More a t tent ion was paid to the production ecology and physiological ecology of water plants, i.e. to those branches which started their act ivi ty during the period evaluated. These studies were st imulated by projects of the IBP and MaB programe.
The annual hemiparasite Euphrasia stricta occurs on Gotland in two early-flowering meadow varieties. E. stricta var. suecica is on the Swedish red-list as endangered, occurring in Sweden only on the Baltic island of Gotland. It probably has near relatives east of the Baltic proper. The other variety, E. stricta var. tenuis, has a wider distribution occurring almost all over Sweden, but is declining in abundance. Both varieties have close morphological similarities and habitat preferences, raising questions about which level conservation efforts should be focused on, varieties or populations. In this study we describe the genetic structure between and within these two varieties using amplified fragment length polymorphism, AFLP. F-ST between varieties is 0.14, and between populations within the varieties E. stricta var. suecica and var. tenuis FST is 0.60 and 0.26 respectively. The partitioning of gene diversity to different levels shows that 14% of the genetic diversity occurs between varieties, 42% between populations within varieties, and 44% within populations. Significant genetic differentiation was detected between varieties, populations and subpopulations within populations using a constrained principal coordinate analysis.We suggest that all of the existing populations of these two varieties on Gotland should be preserved, since they are few (6 E. stricta var. suecica and 5 E. stricta var. tenuis) and much of the genetic diversity is partitioned between populations.
Parasitic plants can significantly influence the species to which they attach. The host response is variable however, and ranges from death of the host to no detectable effects in terms of both growth and physiology. The parasite can directly influence its hosts through resource abstraction, and indirectly by influencing inter- and intra-specific interactions. Abiotic factors interact with these direct and indirect effects to moderate the potential outcome of the host parasite interaction. This paper sets out to review a series of experiments that have been undertaken in our laboratory over a number of years that examine these effects and help us to understand mechanisms underpinning the variability in host response.
Pedicularis dendrothauma is an arboreal epiphytic hemiparasite that was recently discovered in Nepal. We present results of preliminary studies on its habitat, demography, hemiparasitism, flower development, and pollination. While showing a strong preference for Abies spectabilis trunks and branches as a substrate, P. dendrothauma also grows on other species of trees and shrubs in the understorey as well as on dead wood on the forest floor, and only very rarely is rooted in soil or on rocks, rooted in a bryophyte layer. Demographic monitoring of the population in 1999 and 2001 allows us to begin to predict longevity, average size of flowering plants, and survivorship and flowering probability on different substrates. We demonstrate that individual plants of P. dendrothauma live at least four, and probably at least five years. Studies of haustoria show that the species has retained its hemiparasitic habit despite having moved from a terrestrial to an arboreal habitat. Flowering probability increases with plant size; an average flowering plant has five leaves and a longest leaf that measures 21.5 cm. Survivorship varies from substrate to substrate, with the greatest survivorship over a two year period occurring in plants growing on living trees. Flowering probability was the same for plants growing on living trees as it was for plants on dead wood. Studies of flower development suggest that plants growing high in the canopy proceeded through the stages of floral development more rapidly than plants nearer ground level. Despite many hours of field observation, the method of pollination remains a mystery; we suggest different possible pollination mechanisms.
Morphological parameters of Festuca rubra clones and their response to differences in the red/far red ratio (R : FR) were investigated in a growth chamber experiment. The twenty-four clones tested came from 15 micro-sites in three neighbouring meadow communities in the Krkonoše Mts. (Czech Republic). The community types were characterized by different canopy height and structure, and by different radiation conditions (relative R : FR) within the canopies. Low R : FR treatment resulted in reduced tillering and stimulated shoot elongation in most of the clones. In some clones, low R : FR ratios stimulated extravaginal tillering and rhizome system formation. The origin of the clones (i.e., community type) explained a part of variation in morphological parameters, but did not explain variation in the response to R : FR levels. Evidence for a consistent relationship between clone performance and radiation environment in the micro-sites from where the clones originated was not found. It seems that there is only limited selection of F. rubra clones (ecotypes) specialized for particular community types and no selection of clones specialized for particular micro-sites within communities.
Euphrasia stricta var.suecica, E. stricta var.tenuis, andRhinanthus serotinus subsp.vernalis are three endangered, hemiparasitic annual herbs found in traditionally managed hay meadows on Gotland, Sweden. We have studied — experimentally and in the field — how some features in the present and traditional management cycle affect their fitness.
The Melampyrum sylvaticum group is a heterogeneous group at the inter- and infra-specific level. A wide range of morphological characters was examined on specimens collected for this study. The corolla size, the corolla colour and the anther length are considered the most important morphological characters at the interspecific taxonomic level. The morphological and molecular variation of the Melampyrum sylvaticum group in the Sudeten, Alps and Carpathians was analyzed. The morphometric study of European populations of Melampyrum sylvaticum group partly clarified the pattern of the variation of selected characters in this region. The RAPD analysis manifests a very similar trend of the population grouping. The combined analysis of morphological and molecular data gives the most explicit results. Central European yellow flowering populations of M. sylvaticum group form two distinctive groups. The first one is an exclusive type of the Alps and of the Hercynian Mountains (except the Sudeten). The second group has its centre of distribution in the eastern part of the Carpathians. This type was described as Melampyrum herbichii from the present Ukrainian Carpathians and was regarded to be endemic to the Eastern and Southern Carpathians. Populations from the Western Carpathians and Sudeten Mts. are polymorphic. They seem to be closer to M herbichii based on the RAPD markers, whereas the morphology of most populations from these regions is closer to M. sylvaticum s.str. The bract shape seems to be important for discrimination between both groups of populations along with the flower characters and a modest ecological differentiation. The Eastern Carpathian Melampyrum saxosum with white corolla is very close to M herbichii based on the studied morphological characters.
This paper gives an overview of current research into the biology of hemiparasiticOrobanchaceae, formerly part of theScrophulariaceae. It is based on presentations and discussions that took place during the First International Symposium on non-weedy hemiparasiticOrobanchaceae in April 2004 in Wageningen. Aspects such as taxonomy and evolution, ecophysiology, population and restoration ecology are discussed, thus identifying challenges for future research. Hemiparasites have very different life histories, and the robust molecular phylogeny will now permit testing hypotheses regarding the evolution of these life histories, degree of parasitism and host specialization. In a number of genera, evolution is in full swing, leading to taxonomical complications, but at the same time offering opportunities for phylogeographical research. In ecophysiology, the challenge is to better understand what makes a good host and to investigate further the chemical signals emitted by the host and their use in regulating parasite development. Finally, the results of sowing hemiparasites to speed up the restoration of nutrient-poor grasslands are still very variable, and we need a more thorough understanding of the factors influencing population dynamics, which should also enable us to devise better management plans for threatened hemiparasitic species.
The genus Rhinanthus ( Orobanchaceae ) consists of annual hemiparasites that occur in a wide range of climates. Patterns of dormancy and germination were studied for six species sampled in areas ranging from the Pyrenees to Northern Scandinavia, and from sea level up to about 2500 m altitude in the Alpine region. Dormancy was broken by a 2 to 6 months period of cold stratification. Optimal temperature and length of the stratification period appeared to vary between and within species. Two patterns of dormancy and germination were distinguished. Seeds of the first group, including the widely distributed R. minor and R. angustifolius , further referred to as the LW group, require a relatively long period of cold stratification. Moreover, their germination is accelerated if they are subjected to a widening range of higher temperatures in the last weeks of the stratification period. In the other species ( R. alectorolophus, R. glacialis, R. mediterraneus and perhaps R. antiquus ) the release of dormancy is completed in a rather short period. Higher temperatures in the last weeks of the stratification period hardly affect the germination process of this SN-group, with short dormancy and no accelerated germination at higher temperatures. In both groups, temperatures above the low values during stratification reduce germination percentages and induce secondary dormancy in non-germinated seeds. The effects strongly vary with timing and temperature. The patterns have a genetic basis and seem to be species-specific. They do not vary with climate conditions, since samples R. minor , whether collected in sub-arctic or sub-alpine areas or at sea level, generally react according to the LW pattern, and samples of R. alectorolophus from areas at sea level up to montane regions according to the SN one. The ecological significance of the various stratification requirements and effects of higher temperatures on germination is discussed in relation to the local climate of the species and the evolutionary history of the genus.
We experimentally demonstrated the ability of three short-lived monocarpic species to vegetatively regenerate (resprout) from roots after severe disturbance. We assessed the relationship between resprouting ability and (1) timing of injury with respect to life-cycle stage (reproductive vs. vegetative plant), life-history mode (annual vs. winter annual) and phenological stage (flowering vs. fruiting plant), (2) nutrient availability, and (3) disturbance severity (removal of all axillary buds Yes/No).In a chamber experiment with the annual or potentially winter annual Rorippa palustris, all injured plants resprouted in all nutrient levels and day-length regimes (day-length regimes simulated conditions of an annual and a winter annual cohort). The number of adventitious buds on roots was positively affected only by injury. The extent of regeneration and amount of regenerated biomass were higher at high nutrient level and long-day regime.In a field experiment with the biennials, Oenothera biennis and Oenothera issleri, both species responded to injuries by resprouting from axillary buds when at least only one axillary bud was still present. However, they were also able to resprout from adventitious buds on roots. Reproductive plants resprouted more frequently at the flowering stage than at the fruiting stage. Resprouting of vegetative plants (rosettes) was equal throughout the year and more frequent than in the reproductive plants.
Taxonomic considerations and nomenclatural adjustments as a part of a revision ofLinaria Mill. undertaken within the “Flora iberica” project are presented. Data on morphology, seed coat surface, chorology, ecology, synonymy and variability of 11 accepted taxa are reported. The following new combinations are proposed:Linaria aeruginea subsp. cardonica (Font Quer)L. Sáez etM. Sainz,Linaria depauperata subsp.ilergabona (M.B. Crespo etV.J. Arán)L. Sáez, andLinaria saturejoides subsp.angustealata (Willmott)L. Sáez etM.B. Crespo.
Flow cytometry was used to determine ploidy levels in the Czech and Slovak taxa of the genusPseudolysimachion (W.D.J. Koch)Opiz (=Veronica auct. p.p.,Scrophulariaceae). In total, 123 populations from the Czech Republic, Slovakia, Ukraine (one locality), Austria (one locality) and Hungary (one locality) were analyzed. InP. maritimum (L.)Á. Löve etD. Löve andP. spicatum (L.)Opiz, two cytotypes were found: diploid (2n=2x=34) and tetraploid (2n=4x=68). In both species the tetraploid cytotype predominated (P. maritimum: 41 tetraploid populations out of 45;P. spicatum: 57 tetraploid populations out of 58). The two cytotypes ofP. maritimum have no taxonomic significance because ploidy level is not obviously correlated with morphology, distribution pattern or ecology. Tetraploid populations ofP. spicatum belong to two morphologically different subspecies, subsp.spicatum and subsp.fischeri Trávníček. The diploid cytotype (one population only) should be provisionally classified as a third subspecies ofP. spicatum, which is morphologically similar to the Asian subsp.porphyrianum (Pavlov)Trávníček. Only diploid plants (2n=2x=34) ofP. orchideum (Crantz)Wraber were found; all 13 populations that were analyzed belong toP. orchideum s.str. One diploid population sample ofP. spurium subsp.foliosum (Waldst. etKit.)Holub (2n=2x=34) and one tetraploid sample ofP. incanum subsp.pallens (Host)Trávníček (2n=4x=68) were also analyzed. In addition, three tetraploid populations of hybrid origin were investigated:P. maritimum ×P. spicatum subsp.spicatum (one population) andP. maritimum ×P. spurium subsp.foliosum (two populations). While hybrid plants ofP. maritimum ×P. spicatum arose from tetraploid parental species, plants ofP. maritimum ×P. spurium probably resulted from a cross between tetraploidP. maritimum and diploidP. spurium. The putative origin and evolutionary importance of polyploids in thePseudolysimachion are discussed.
For the first time, a tentative overview of described plant communities in Denmark is presented according to the phytosociological Braun-Blanquet approach. An attempt was made to compile all available names of syntaxa at the association level, which have appeared in the literature, mostly as defined from vascular plants and the Charetea. In total 173 associations belonging to 38 classes have been registered in Denmark. The listed associations are characterized by a brief description of their ecology, Danish distribution and rarity. Basic literature sources for each syntaxon are provided. The current knowledge of Danish plant communities is discussed. It is concluded that the number of known syntaxa from Denmark is probably underestimated.
Genetic diversity in a sample of an aquatic plant Butomus umbellatus from 37 localities in Czechia and Slovakia was studied by analyzing six polymorphic loci in three enzymatic systems (SKDH, PGD and AAT). Diversity among ramets was low in eight populations with relatively extensive sampling (only one population possessed more than one multilocus genotype), suggesting high clonality of reproduction in these populations. However, among-population diversity was high: G = 0.782 and 0.881 for the samples of diploid and triploid populations, respectively. Heterozygosity of individual plants averaged over variable loci was also high: H = 0.554 for diploids and 0.453 for triploids. Genetic differentiation among populations was additionally studied using cluster analysis. Several populations of diploids clustered separately from all other populations, whereas another group of diploid populations clustered with some triploid populations, indicating the possibility of relatively recent, probably multiple origin of these triploid populations. from their diploid progenitors. Association between matrices of Nei's genetic distances among populations from different localities and matrices of geographic distances among these localities revealed highly significant correlation for the sample of diploid populations (r = 0.60, P < 0.001) but no significant correlation for the sample of triploid populations (r = 0.02, P = 0.593). These results indicate a spatial structure of diploid populations in accordance with the isolation by distance model, and a random distribution of genotypes among triploid populations of B. umbellatus.
