Growth forms of biennial and pluriennial vascular plants in central Europe

The growth forms of bi- and pluriennial central European plant species were analyzed and summarized systematically by means of a dichotomous key. Ten growth forms are distinguished according to vegetative morphological characters of the plants: holoparasitic erosulate, (simple) erosulate, floating semirosette, succulent semirosette, tufted semirosette, (simple) semirosette, storage root semirosette, tuber semirosette, storage root rosette, and (simple) rosette bi- or pluriennial plants. Only very few species are strictly biennial or pluriennial. Each individual plant can be assigned to only one growth form system according to the life span (the system of bi-and pluriennials in the present case). However, several species include individuals that behave as annuals as well as biennials/pluriennials and/or periennials. The term "hapaxanthic" is discussed concerning to its reference level in relation to the plant organism. Three types of hapaxanthy can be distinguished in this context: Genet hapaxanthy with and without vegetative reproduction and ramet hapaxanthy.     

Growth form evolution and shifting habitat specialization in annual plants

Optimal plant growth form should vary across environments. We examined the potential for mutations causing large changes in growth form to produce new optimal phenotypes across light environments. We predicted that the upright growth form would be favoured in a light limiting environment as leaves were in a position to maximize light interception, while a rosette (leaves in a basal position) growth form would be favoured in a high light environment. Growth form genotypes of Brassica rapa (upright wild-type and rosette mutants) and Arabidopsis thaliana (large rosette wild-type and increasingly upright growth form mutants) were grown in a greenhouse in control (ambient) and filtered (low) light treatments. Compared to upright genotypes, rosette genotypes had relatively high fitness in control light but had a relatively large fitness reduction in filtered light. Our results demonstrate the potential importance of rapid growth form evolution in plant adaptation to new or changing environments.     

Tourism and recreation: a common threat to IUCN red-listed vascular plants in Europe

Tourism and recreation are large industries employing millions of people and contribute over US$2.01 trillion to the global economy. Unfortunately they also have diverse and sometimes severe environmental impacts affecting many species, including those that are rare and threatened. To assess the extent to which these industries threaten vascular plants, we reviewed data in the IUCN Red List for 462 Critically Endangered, Endangered and Vulnerable European species. Tourism and recreation were listed as threatening 42 % (194 species) of these species from across 50 families, mostly herbs (70 %). They were listed as threatening plants in 9 of the 10 bioregions in Europe and in 25 of the 40 countries assessed. Popular tourism destinations such as the Canary Islands (41 species) and mainland Spain (40 species) had the greatest diversity of species listed as threatened by tourism and recreation. The most common of these threats were trampling (61 species), plant collection (59), the maintenance/construction of tourist infrastructure (43) and habitat degradation due to the urbanisation of tourist sites (13). Additional species assessments and more research on the impacts of tourism and recreation may add to these values. It is clear that these industries pose an important threatening process on plants in Europe based on the IUCN Red List data and hence deserve greater recognition in terms of research, conservation and management.     

The contribution of crassulacean acid metabolism to the annual productivity of two aquatic vascular plants

Summary Net annual productivity and annual carbon budgets were determined for populations of Littorella uniflora var. americana and Isoetes macrospora in a mesotrophic and oligotrophic lake in northern Wisconsin, to assess the contribution of Crassulacean Acid Metabolism (CAM) to annual productivity of the species in their natural environment. Nocturnal carbon accumulation (CAM), daytime uptake of external CO₂ via the C₃ mechanism, and refixation of endogenously generated CO₂ from daytime respiration were the sources of carbon income. CAM activity as diurnal acid rhythms reached maxima of 89 to 182 eq·g^-1 leaf fresh weight for the various populations.Maximum rates of daytime ¹⁴C uptake ranged from 0.56 to 1.46 mg C·g^-1 leaf dry wt.·h^-1 for the study populations. Refixation of daytime respired CO₂ averaged 37% for the four populations. Carbon loss was due largely to dark respiration, during the day and night. Nocturnal carbon accumulation, daytime CO₂ uptake and 24-h dark respiration were of similar magnitude, indicating dark respiration was equivalent to 50% of gross photosynthesis.Net annual production was measured for each population by following leaf turnover. Turnover rates for the Littorella populations were 1.56 and 1.72·yr^-1, and for the Isoetes populations, 0.85 and 1.00·yr^-1. Measured net annual productivity and calculated net annual productivity (based on carbon exchange) agreed within an average of 12% for the four populations. While CAM activity was greater for the more productive population of each species, the results suggest that the contribution of CAM to annual productivity is greater for the less productive population of each species. CAM contributed 45 to 55% of the annual carbon gain for the study populations.     

The evolution of competitive strategies in annual plants

Annual plants are common in disturbed habitats. It is frequently assumed that because these habitats often have low-plant density, competition is not important in shaping the ecological strategies of annual plants. We test for competitive strategies in genotypes of the short-lived annual plant Arabidopsis thaliana. Genotypes were grown in treatments with or without conspecific competitors. We measured size at reproduction and fitness (fruit production) at final development. We estimated competitive ability in each genotype at first reproduction (the ability to maintain size in the presence of competitors) and at final development (the ability to maintain fruit production in the presence of competitors). Genotypes showed relatively high competitive ability measured as fruit production at final development, but most genotypes had low competitive ability measured as size at reproduction. Our results suggest that competition has been important in the evolution of strategies in these genotypes but vegetative size is not a strong predictor of competitive ability. Rather, competitive ability is determined by the capacity to reproduce efficiently in the presence of competitors. The competitive strategies expressed across these genotypes suggest that competition has been a selective force in these plants, and that a fast life history is not equivalent to an “r-strategy.”     

Protochlorophyll forms in roots of dark-grown plants

Protochlorophyll was found in roots of dark-grown plants of seven species investigated. It was identified by absorbance and fluorescence spectra of acetone and ether extracts. Chlorophyll was also found in roots of one pea species. The concentration of protochlorophyll was usually highest in young root tips and decreased upwards along the roots. The maxima of the in vivo absorbance spectra of the species studied varied between 634 and 638 nm. Low temperature in vivo fluorescence emission spectra had two maxima, one at ca 633 and the other at ca 642 nm, when the wavelengths of the excitation light were 440 and 460 nm, respectively. In vivo fluorescence excitation spectra displayed a shift of the excitation maximum from 438 to 445 nm, when emission varied from 620 to 647.5 nm. Deconvolution of these three types of spectra into Gaussian components made it possible to identify two spectral forms of protochlorophyll: protochlorophyll_629–633 and protochlorophyll_638–642.     

Alien plants in central Australia

The central Australian flora currently contains 78 alien species, of which 17 are predominantly summer-growing, 19 are southern winter-growing species reaching roadsides, stockyards and watercourses in the southern Northern Territory and 42 are at present confined to gardens in Alice Springs. A further 11 species reach the far north of South Australia or die far southwest of Queensland but not the Northern Territory. The central Australian alien flora may be classified by growing season and drought-tolerance, or broadly categorized on the basis of habitat and dispersal agent into 'garden weeds', 'tourist weeds' and 'stock weeds'. Present ecological knowledge of central Australian aliens is limited, but indicates that whilst some will probably remain confined to better-watered habitats, many are likely to spread into the arid areas, becoming obvious only after a succession of wet years. The central Australian alien flora is increasing at present and this increase is expected to continue.     

Signal transduction in vascular plants

We review current evidence for the presence and activity in plants of several paradigmatic components of transmembrane signal transduction systems. Components considered include the second messengers calcium, inositol 1,4,5-trisphosphate, and cyclic AMP; protein kinases and protein phosphatases; and G-proteins. At the current stage of development of the field of plant signal transduction, broad similarities between plant and the more well-studied animal systems are apparent. However, there also exist considerable differences in detail.     

Optimal phenology of annual plants under grazing pressure

Plants show phenological responses to herbivory. Some enclosure experiments have demonstrated that the onset of the peak flowering season is dependent on grazing pressure. We constructed a mathematical model using Pontryargin's maximum principle to investigate changes in flowering time by examining shifts in resource allocation from vegetative to reproductive plant components. We represented a primary production of a plant individual by two types of function of vegetative part size, a linear function and a convex non-linear function. The results of a linear production model indicate that optimal phenology follows a schedule that switches from the production of vegetative parts to that of reproductive parts at a given time ('bang-bang' control). However, in a non-linear model, a singular control, wherein the plant invests in both productive and reproductive parts, may be included between obligate production and reproduction periods. We assumed that the peak of the flowering season occurs immediately following the exclusive investment in reproduction. In a linear production model, differential herbivory rates on the vegetative and reproductive parts of a plant resulted in shifts in the peak flowering time. A higher herbivory rate on the vegetative components advanced the peak, whereas it was delayed when grazing pressure focused on reproductive components of the plant. In the non-linear production model, increased grazing pressure tended to postpone the flowering peak. These results corresponded well with results of enclosure experiments, thus suggesting adaptive control of flowering time in plants.     

Antimicrobial activity of vascular plants

Numerous surveys have demonstrated the wide occurrence of active antimicrobial substances in higher plants. The array of compounds with unique structures which plants produce has served as a stimulus to continued search for useful antibiotics. Reports referred to in the table indicate that active substances have been found in plants from 157 families.     

Aquatic vascular plants in Japanese lakes

This data paper describes the native vascular aquatic plant floras of 268 Japanese lakes recorded from 1899–2011. The data were compiled from 201 literature sources, most of which were written in Japanese and published in local journals or individual reports rather than in major scientific journals. The literature was searched using web-based services (i.e., Google Scholar, http://scholar.google.com/; CiNii, http://ci.nii.ac.jp/en; JDreamII, http://pr.jst.go.jp/jdream2/; and ISI, http://apps.webofknowledge.com) and by private communication with experts or local governments. Scientific names were consolidated under currently-accepted nomenclature. Four datasets, FloraDB, LakeDB, SpeciesDB, and LiteratureDB, were created to include records of the flora of each lake in each year, the names and locations of the lakes, the scientific names and synonyms of the aquatic vascular plants, and a literature list, respectively. These data can be used to study long-term changes in the species composition and/or richness of aquatic plants in Japanese lakes.     

The relationships of vascular plants

Recent phylogenetic research indicates that vascular plants evolved from bryophyte-like ancestors and that this involved extensive modifications to the life cycle. These conclusions are supported by a range of systematic data, including gene sequences, as well as evidence from comparative morphology and the fossil record. Within vascular plants, there is compelling evidence for two major clades, which have been termed lycophytes (clubmosses) and euphyllophytes (seed plants, ferns, horsetails). The implications of recent phylogenetic work are discussed with reference to life cycle evolution and the interpretation of stratigraphic inconsistencies in the early fossil record of land plants. Life cycles are shown to have passed through an isomorphic phase in the early stages of vascular plant evolution. Thus, the gametophyte generation of all living vascular plants is the product of massive morphological reduction. Phylogenetic research corroborates earlier suggestions of a major representational bias in the early fossil record. Mega-fossils document a sequence of appearance of groups that is at odds with that predicted by cladogram topology. It is argued here that the pattern of appearance and diversification of plant megafossils owes more to changing geological conditions than to rapid biological diversification.