Leontodon Hispidus Research Articles

Changes in species composition of European acid grasslands observed along a gradient of nitrogen deposition

Question: Which environmental variables affect floristic species composition of acid grasslands in the Atlantic biogeographic region of Europe along a gradient of atmospheric N deposition? Location: Transect across the Atlantic biogeographic region of Europe including Ireland, Great Britain, Isle of Man, France, Belgium, The Netherlands, Germany, Norway, Denmark and Sweden. Materials and Methods: In 153 acid grasslands we assessed plant and bryophyte species composition, soil chemistry (pH, base cations, metals, nitrate and ammonium concentrations, total C and N, and Olsen plant available phosphorus), climatic variables, N deposition and S deposition. Ordination and variation partitioning were used to determine the relative importance of different drivers on the species composition of the studied grasslands. Results: Climate, soil and deposition variables explained 24% of the total variation in species composition. Variance partitioning showed that soil variables explained the most variation in the data set and that climate and geographic variables accounted for slightly less variation. Deposition variables (N and S deposition) explained 9.8% of the variation in the ordination. Species positively associated with N deposition included Holcus mollis and Leontodon hispidus. Species negatively associated with N deposition included Agrostis curtisii, Leontodon autumnalis, Campanula rotundifolia and Hylocomium splendens. Conclusion: Although secondary to climate gradients and soil biogeochemistry, and not as strong as for species richness, the impact of N and S deposition on species composition can be detected in acid grasslands, influencing community composition both directly and indirectly, presumably through soil-mediated effects.

Antioxidant and Antihemolytic Activities of Leontodon Hispidos

ABSTRACTIn this study, antioxidant and antihemolytic activities of aerial parts of Leontodon hispidus hydroalcoholic extract were investigated with different in vitro assay systems. Extracts showed good antioxidant activity. IC50 for DPPH radical-scavenging activity was 241.3±7.91 μg/ml. Extracts showed moderate Fe2+ chelating ability (IC50=683.1±23.22 μg/ml). Extracts exhibited good antioxidant activity in hemoglobin induced linoleic acid model and also it was capable to scavenge hydrogen peroxide in a concentration dependent manner. Extracts showed good antihemolytic activity againts H2O2 induced hemolysis (IC50=364.1±10.55 μg/ml). The total amount of phenolic compounds in the extract was determined as gallic acid equivalents and total flavonoid content was calculated as quercetin equivalents from a calibration curve. Also cumarin was determined by HPLC/DAD.

Ethnobotany of Food Plants in the High River Ter Valley (Pyrenees, Catalonia, Iberian Peninsula): Non-Crop Food Vascular Plants and Crop Food Plants with Medicinal Properties

The present study reports a part of the findings of an ethnobotanical research project conducted in the Catalan region of the high river Ter valley (Iberian Peninsula), concerning the use of wild vascular plants as food and the medicinal uses of both wild and cultivated food plants. We have detected 100 species which are or have been consumed in this region, 83 of which are treated here (the remaining are the cultivated food plants without additional medicinal uses). Some of them, such as Achillea ptarmica subsp. pyrenaica, Convolvulus arvensis, Leontodon hispidus, Molopospermum peloponnesiacum and Taraxacum dissectum, have not been previously reported, or have only very rarely been cited or indicated as plant foods in very restricted geographical areas. Several of these edible wild plants have a therapeutic use attributed to them by local people, making them a kind of functional food. They are usually eaten raw, dressed in salads or cooked; the elaboration of products from these species such as liquors or marmalades is a common practice in the region. The consumption of these resources is still fairly alive in popular practice, as is the existence of homegardens, where many of these plants are cultivated for private consumption.

Ozone suppresses soil drying‐ and abscisic acid (ABA)‐induced stomatal closure via an ethylene‐dependent mechanism

Elevated atmospheric ozone concentrations (70 ppb) reduced the sensitivity of stomatal closure to abscisic acid (ABA) in Leontodon hispidus after at least 24 h exposure (1) when detached leaves were fed ABA, and (2) when intact plants were sprayed or injected with ABA. They also reduced the sensitivity of stomatal closure to soil drying around the roots. Such effects could already be occurring under current northern hemisphere peak ambient ozone concentrations. Leaves detached from plants which had been exposed to elevated ozone concentrations generated higher concentrations of ethylene, although leaf tissue ABA concentrations were unaffected. When intact plants were pretreated with the ethylene receptor binding antagonist 1-methylcyclopropene, the stomatal response to both applied ABA and soil drying was fully restored in the presence of elevated ozone. Implications of ethylene's antagonism of the stomatal response to ABA under oxidative stress are discussed. We suggest that this may be one mechanism whereby elevated ozone induces visible injury in sensitive species. We emphasize that drought linked to climate change and tropospheric ozone pollution, are both escalating problems. Ozone will exacerbate the deleterious effects of drought on the many plant species including valuable crops that respond to this pollutant by emitting more ethylene.

Chronic exposure to increasing background ozone impairs stomatal functioning in grassland species

AbstractTwo species found in temperate calcareous and mesotrophic grasslands (Dactylis glomerata and Leontodon hispidus) were exposed to eight ozone treatments spanning preindustrial to post‐2100 regimes, and late‐season effects on stomatal functioning were investigated. The plants were grown as a mixed community in 14 L containers and were exposed to ozone in ventilated solardomes (dome‐shaped greenhouses) for 20 weeks from early May to late September 2007. Ozone exposures were based on O3 concentrations from a nearby upland area, and provided the following seasonal 24 h means: 21.4, 39.9 (simulated ambient), 50.2, 59.4, 74.9, 83.3, 101.3 and 102.5 ppb. In both species, stomatal conductance of undamaged inner canopy leaves developing since a midseason cutback increased linearly with increasing background ozone concentration. Imposition of severe water stress by leaf excision indicated that increasing background ozone concentration decreased the ability of leaves to limit water loss, implying impaired stomatal control. The threshold ozone concentrations for these effects were 15–40 ppb above current ambient in upland UK, and were within the range of ozone concentrations anticipated for much of Europe by the latter part of this century. The potential mechanism behind the impaired stomatal functioning was investigated using a transpiration assay. Unlike for lower ozone treatments, apparently healthy green leaves of L. hispidus that had developed in the 101.3 ppb treatment did not close their stomata in response to 1.5 μm abscisic acid (ABA); indeed stomatal opening initially occurred in this treatment. Thus, ozone appears to be disrupting the ABA‐induced signal transduction pathway for stomatal control thereby reducing the ability of plants to respond to drought. These results have potentially wide‐reaching implications for the functioning of communities under global warming where periods of soil drying and episodes of high vapour pressure deficit are likely to be more severe.

Timing of cotyledon damage affects growth and flowering in mature plants

Although the effects of herbivory on plant fitness are strongly linked to age, we understand little about how the timing of herbivory at the seedling stage affects growth and reproduction for plants that survive attack. In this study, we subjected six north-western European, dicotyledonous grassland species (Leontodon autumnalis, Leontodon hispidus, Plantago lanceolata, Plantago major, Trifolium pratense and Trifolium repens) to cotyledon removal at 7, 14 and 21 d old. We monitored subsequent growth and flowering (number of inflorescences recorded, and time taken for first flowers to open) over a 107 d period. Cotyledon removal reduced growth during establishment (35 d) for all species, and a further three exhibited reduced growth at maturity. Four species developed fewer inflorescences, or had delayed flowering after cotyledon removal. Although early damage (7 d old) had the greatest long-term effect on plant performance, responses varied according to the age at which the damage occurred and the species involved. Our results illustrate how growth and flowering into the mature phase is affected by cotyledon damage during different stages of seedling ontogeny, and we highlight the ways in which ontogenetic variation in seedling tolerance of tissue loss might impact upon plant fitness in mature plant communities.

Chemical composition and net energy content of alpine pasture species during the grazing season

The aim of this study was to investigate changes over time in chemical composition, digestibility and net energy for lactation (NEl) contents of 12 species of alpine pastures during the vegetative season ( i.e., Agrostis tenuis, Anthoxanthum alpinum, Carex sempervirens, Festuca rubra, Nardus stricta, Phleum alpinum, Poa alpina, Poa violacea, Alchemilla vulgaris, Leontodon hispidus, Potentilla aurea, Trifolium repens). Wild seeds were collected from plants spontaneously occurring in mountain pastures in North-East Italy and sown in a greenhouse. Plants were transplanted in open main field plots. Each main plot was divided into sub-plots, which were cut (first cut) in succession every 10 days in two consecutive years. Herbage regrowth (second cut) was evaluated at 45, 60 and 75 days after first cut. Herbage samples were analysed for chemical composition, for in vitro organic matter digestibility (OMD), and the NEl content was estimated. During the pasture utilisation period ( i.e., thermic sum between 500 and 1200 °C) the species had limited variation in their average CP contents (81–109 g/kg DM) excluding the lowest values of F. rubra and P. violacea (74 and 71 g/kg DM, respectively; P<0.05) and the highest value of T. repens (202 g/kg DM; P<0.05). Within grasses, there were very fibrous species (>700 g NDF/kg DM, such as F. rubra, N. stricta and P. violacea) and species with medium contents (573–664 g NDF/kg DM), while forbs and the legume specie had a low content (≤403 g NDF/kg DM). The OMD ranged from P. violacea (256 g/kg DM; P<0.05) to T. repens (730 g/kg DM; P<0.05). The highest NEl content was for T. repens (6.3 MJ/kg DM; P<0.05), while low NEl values were calculated for N. stricta and C. sempervirens (2.9 and 2.5 MJ/kg DM, respectively). The lowest (P<0.05) NEl content was estimated for P. violacea (1.9 MJ/kg DM). Most species investigated (in particular, Agrostis tenuis, F. rubra, L. hispidus, Potentilla aurea), had an initial intense decrease in the CP content with advancing season, reaching minimum levels at the thermic sum of 800–1000 °C. During season advancement, all species had increased NDF content, with marked increments for F. rubra and Poa species, and all species had decreased NEl contents. Regrowth samples collected at 75 days after first cut had lower CP and NEl contents relative to those collected after 45 days from the first cut (140 g/kg versus 160 g/kg DM and 4.4 MJ/kg versus 4.8 MJ/kg DM, respectively; P<0.05). This study provides nutritional information on individual herbage species of alpine pastures at different vegetative phases which can be used to obtain average nutritional values of use in pasture management work.

Adaptive adjustments to light in foliage and whole-plant characteristics depend on relative age in the perennial herb Leontodon hispidus.

• Growth form gradually changes during ontogeny through juvenile, reproductive, and senescent phases in perennial herbs, but resulting effects on plant structure, functioning and role in the community are poorly characterized. Here, biomass distribution, leaf structure and nutrients were studied in relation to irradiance and age state in the temperate meadow perennial Leontodon hispidus in the field. • Plant ontogeny modified plastic responses to irradiance with most plastic changes in leaf dry mass per area in reproductive and most plastic LAR alterations in young individuals. Due to age-dependent changes, light interception efficiency was maximised in young, and photosynthetic potential in reproductive specimens, while senescent plants had inferior light interception and use, but were probably more competitive for below-ground resources. • Species age spectrum shifted to senescent phases, and the fractional biomass to below-ground in sites with higher species richness. • These results collectively demonstrate a strong effect of ontogeny on dry matter partitioning, leaf architecture and functioning, and plastic adjustments in these traits and suggest that species competitive potentials change through the ontogeny.

Simulated pollutant nitrogen deposition increases P demand and enhances root‐surface phosphatase activities of three plant functional types in a calcareous grassland

Summary • The effects of 7 yr enhanced nitrogen (N) deposition (3.5–14 g N m−2 yr−1) in combination with phosphorus (P) additions, on growth, shoot N and P content, and root-surface phosphomonoesterase (PME) activities were determined along with mycorrhizal infection rates in seedlings of a sedge (Carex flacca), grass (Koeleria macrantha) and forb (Leontodon hispidus). • Seedlings were grown for 14–28 d in mesh-walled cores inserted into turfs from treated field plots enabling complete root recovery. • After 14 d, root-surface PME activity was typically more than doubled by 3.5 and 14 g N m−2 yr−1, and by 28 d the N treatments consistently gave dose-dependent effects. PME activity was reduced by P additions in the sedge and grass by 55 and 65%, respectively, and correlated with soil and shoot N and P concentrations, again most strongly in the sedge and grass. Mycorrhizal infection was least in the sedge (1%) and greater in the grass (49%) and forb (76%). • Long-term N enrichment of calcareous grassland stimulates root-surface PME in representatives of the three major higher-plant functional types. PME response to P additions was greatest in least mycorrhizal-dependant species with roots more adapted for direct P uptake.

Karyotaxonomy of Greek serpentine angiosperms

The chromosome numbers are given for 20 angiosperm taxa, most of which grow predominately or exclusively on serpentine in Greece, and the karyotype morphology is illustrated in all cases but one. Chromosome data are provided for the first time for ten taxa (Alyssum pogonocarpum, Centaurea charrellii, C. vlachorum, Cephalaria fanourii, Matricaria tempskyana, Onosma stridii, Scorzonera doriae, Silene fabarioides, S. salamandra, Trinia glauca ssp. pindica) and for the endemic monospecific genus Leptoplax. A new number is reported for Thymus teucrioides ssp. candilicus. An unexpected dysploid number is recorded for a population of Leontodon hispidus ssp. hispidus. Chromosome number and karyotype details from Greek populations are presented for the rest of the taxa. Chromosomal evidence supports close relationships among members of Onosma subsect. Asterotricha. The unusual chromosome number of Centaurea vlachorum supports its placement either in C. sect. Jacea or C. sect. Cyanus. The evolution of taxa in sections Vierhapperia, Pulvinares, and Nervosae of Scorzonera appears to be connected with particular chromosomal rearrangements and dysploidy. Leptoplax does not share the same chromosome number with Peltaria but with Bornmuellera instead, something that facilitates infrageneric hybridization. Further issues of taxonomy, distribution, evolution and conservation of serpentine species are briefly discussed where appropriate. © 2002 The Linnean Society of London, Botanical Journal of the Linnean Society, 2002, 139, 109–124.

Changes in stomatal behaviour in the calcicole Leontodon hispidus due to the disruption by ozone of the regulation of apoplastic Ca2+ by trichomes.

Regulation of the concentration of Ca2+ in the apoplast of plants is essential in order to allow Ca(2+)-dependent processes, such as Ca(2+)-mediated signal transduction in stomatal guard cells, to function correctly. This is particularly important for plants growing with high levels of Ca2+ in the rhizosphere. Recently, we have shown that in two calcicoles, Leontodon hispidus L. and Centaurea scabiosa L., trichomes play a key role in this regulatory process. Ozone is known to have a marked effect on plant Ca2+ homeostasis. Therefore, we have examined the effect of this pollutant on the regulation by trichomes of apoplastic Ca2+ in the calcicole L. hispidus. Treatment with 100 nl l-1 ozone resulted in a reduction in stomatal conductance of approximately 25% in plants grown with 15 mM Ca2+ in the rhizosphere. Analysis of total Ca2+ levels revealed that these changes in stomatal behaviour reflect a decrease in the ability of trichomes to sequester Ca2+. The amount of Ca2+ present in the trichome tip cell was reduced by approximately 38%. This was accompanied by an increase in the levels of Ca2+ in the guard cells and other tissues of the leaf. These data suggest that ozone has a detrimental effect on the ability of trichomes to regulate the concentration of apoplastic Ca2+ in L. hispidus, resulting in altered stomatal behaviour, and hence gaseous exchange, possibly due to the disruption of guard-cell Ca(2+)-mediated signal transduction. This has important implications for the growth and survival of plants growing in Ca(2+)-rich soils.

Evaluation of chemosystematic characters in the genus Leontodon (Asteraceae)

SummaryZidorn, C. &amp; Stuppner, H.: Evaluation of chemosystematic characters in the genus Leontodon (Asteraceae). ‐‐ Taxon 50: 115–133. 2001. – ISSN 0040‐0262.Flavonoids, phenolic acids and sesquiterpene lactones were evaluated as qualitative and quantitative chemosystematic markers in the genus Leontodon by HPLC‐UV and HPLC‐MS analyses. One population of Leontodon hispidus L. showed a high degree of variation between different plant organs and between different individuals. Seasonal variation of phenolic acids in the leaves and of sesquiterpene lactones in the rhizomes was also pronounced. In contrast, phenolics in the heads were present in nearly constant amounts during the flowering period. Within species, analyses of samples originating from different altitudes (13 samples of L. helveticus from 1600–2950 m, 19 samples of L. autumnalis from 30–2075 m, and 61 samples of L. hispidus from 40–2550 m) exhibited a significant positive correlation between altitude of the collection sites and total content of flavonoids. Unlike flavonoids, the phenolic acids showed no significant altitudinal variation. The data reveal more pronounced variation between rather than within species.

Anti-inflammatory activities of hypocretenolides from Leontodon hispidus.

Hypocretenolides, a small group of sesquiterpene lactones with an unusual ring structure, are constituents of a small number of species from the Lactuceae tribe (Asteraceae). Three biogenetically closely related 14-hypocretenolides from Leontodon hispidus L. were investigated for a putative anti-inflammatory activity. 14-Hydroxyhypocretenolide-beta-D-glucoside-4'-14"-hydroxyhypocr etenoate significantly exhibited in vivo anti-inflammatory activity in the croton oil-induced mouse ear edema. To obtain first information regarding the molecular targets which might be affected by this constituent, two in vitro bioassays were performed: (i) DNA binding activity of the transcription factor NF-kappa B was evaluated by electrophoretic mobility shift assay (EMSA) using TNF-alpha-activated Jurkat T cells and (ii) nitrite accumulation in cell culture supernatants of LPS-activated RAW 264.7 macrophages was determined as a parameter for inducible nitric oxide synthase (iNOS)-dependent nitric oxide release. In order to gain information about structure-activity relationships, additionally the aglycone 14-hydroxyhypocretenolide and its D-glycoside were investigated in these in vitro systems. 14-Hydroxyhypocretenolide-beta-D-glucoside-4'-14"-hydroxyhypocr etenoate as well as its aglycone exhibited activity in both test systems, whereas the D-glucoside was not or only weakly active.

Cypripedium calceolus L.

A perennial herb with horizontal rhizome (diameter about 6mm) up to 10cm underground. Roots long and fleshy, diameter up to 2mm. Stem 20-60(70) cm, glandular-pubescent with brown basal sheaths; leaves 3-5, elliptical to ovate-oblong, acute to acuminate, sparsely pubescent (oval lanceolate, somewhat pleated, large), (7)11-17(22) cm long, (3)5.58(10) cm wide, veins obvious, bracts leaf-like, exceeding flowers; flowers 1-2(3) large; perianth segments purple-brown; dorsal outer tepal ('sepal') lanceolate, suberect, 3.5-6cm long and 1.5-2.5 cm wide; lateral 'sepals' joined, hanging below labellum 3.5-5.5 cm, free tips up to 5mm; inner tepals ('petals') 4-7 cm long and 0.5-1 cm wide, horizontal, twisted; labellum yellow, shoe-shaped (length 34cm, width 2-3 cm, depth 1.5-2 cm), reflexed, covered with viscous hairs inside, not spurred; staminode petaloid shield-shaped, white with red spots, 1-1.2 cm long, 0.7-0.9 cm wide; ovary elongate, somewhat curved, pubescent (glandular hairs), not twisted, pedicellate. Two fertile anthers, one on each side of style; stigma and staminode forming a flat appendage on the front of the column. Capsule up to 3 cm long and about 0.9 cm in diameter, containing 6000-17 000 seeds; seeds oblong about 1 mm long with a mass of a few micrograms (seed volume 0.02 mm3). From continental Europe, the all-yellow flowered var. fiavum Rion has been recorded (Davies et al. 1984). This exceedingly rare orchid was formerly more widespread in northern England in limestone woodland; it is more plentiful in wooded sites in northern Europe, but everywhere has suffered from collecting.

Cytotoxic activities of hypocretenolides from Leontodon hispidus.

The hypocretenolides are a small group of sesquiterpene lactones with an unusual ring structure and are constituents of several species from the tribe Lactuceae of the family Asteraceae. In the present communication we report on the cytotoxic effects of three hypocretenolides (1-3) from Leontodon hispidus on: (a) eight solid-tumor cell lines (A431, HEP2, MCF7, OVCAR3, SK28, SK37, SW872, ZR75-1), tested by a (3)H-thymidine incorporation assay; (b) two different leukemia cell lines (GTB, HL60), measured by a MTT assay; and (c) CD34(+) bone-marrow cells, assessed by scoring the number of colonies derived from primitive and late erythroid progenitors (BFU-E and CFU-E) as well as from granulocytic/macrophagic progenitor cells (CFU-GM). The aglycon 14-hydroxyhypocretenolide (1) exhibited pronounced activities, although its beta-D-glucoside (2) showed no activity, even at the highest concentration tested (2 microM). 14-Hydroxyhypocretenolide-beta-D-glucoside-4',14' '-hydroxyhypocretenoate (3), the ester of the glucoside esterified with the open-chain form of the aglycon, was the most potently cytotoxic substance and proved to be even more active than the positive-control substance helenalin.

How well do plant traits correlate with establishment ability? Evidence from a study of 16 calcareous grassland species

The ability of 16 calcareous grassland species to establish in competition with adult neighbours of two different growth forms was assessed in a glasshouse experiment. The questions asked were: (1) how well is establishment ability related to plant traits such as seed mass, DNA content, relative growth rate and adult height; and (2) are the results consistent across different neighbours? Two measures of establishment ability were calculated, survival relative yield and biomass relative yield, for seedlings grown with a dicot. (Leontodon hispidus) and with a graminoid (Festuca ovina). The results depended on which measure of establishment ability was used. When establishment ability was measured in terms of biomass relative yield, seed mass was a good predictive trait, accounting for 38–55% of variation. However, when establishment ability was measured as survival relative yield, adult height was found to be the best predictor, capable of accounting for 20% of variation, although this was not consistent across neighbours. Thus, no clear relationship between plant traits and establishment ability was found: results depended on the measure of establishment ability used, and in the case of adult height, on the identity of the neighbour species. Survival relative yield was strongly associated with target and neighbour species growth form type, with stronger suppression of like than of non‐like growth forms. The lack of strong relationships between plant traits and establishment ability, and the dependence on neighbour identity, suggests that the links between plant traits and establishment might be context‐dependent; thus an understanding of the mechanisms underlying any such links is essential.

Comparison of lead tolerance in Allium cepa with other plant species

Our previous studies demonstrated increased lead tolerance of Allium cepa adventitious root tip cells during treatment with lead. We then compared the degree of tolerance to lead of A. cepa and 22 groups of plants (species, varieties, populations). We showed that initially, constitutional tolerance of A. cepa to lead was moderate, then high, similar to inducible tolerance of calamine waste heap plants. It is noteworthy that this high tolerance was characteristic for only A. cepa plants developing from bulbs. Plants developing from seeds demonstrated a lower tolerance to lead (by 7 to 45%). The high constitutional tolerance of A. cepa growing from bulbs was related to the possibility of transporting large amounts of lead (40%) from the roots to the bulb. These results point to the role played by the storage organ (bulb) in raising the tolerance of A. cepa to lead, which is demonstrated for the first time in this study, and which is interpreted as an element of constitutional tolerance to lead. It was found that the constitutional tolerance of crop plants ranged from 78 to 2%, depending on the species, variety, development stage, and duration of treatment with lead. The inducible tolerance of plants from the waste heap ranged from 130 to 10%. In these plants, the increased tolerance resulting from the adaptation to growing on a polluted waste heap averaged 18.5%. The following order of decreasing tolerance to lead was found: I. Species with the highest tolerance, i.e. with inducible tolerance, from the waste heap: Silene vulgaris> Biscutella laevigata> Leontodon hispidus. II. Species with high constitutional tolerance: B. laevigata natural population> A. cepa growing from bulbs> Hordeum vulgare> Zea mays. III. Species with intermediate, most common, constitutional tolerance: A. cepa growing from seeds> Triticum vulgare> Pisum sativum> Cucumis sativus> Lupinus luteus> Raphanus sativus> Secale cereale. IV. Species with low constitutional tolerance: Brassica napus> Soja hispida> Phaseolus vulgaris. The species, varieties and populations differed considerably among each other in terms of lead uptake. Although no relationship was found between the degree of tolerance to lead and the amount of lead in a plant's tissues, the pattern of lead distribution was similar in almost all of the plants.

The regulation of apoplastic calcium in relation to intracellular signalling in stomatal guard cells

AbstractIt is now well established that calcium has a substantive role in intracellular signalling in stomatal guard cells. Much less attention has, however, been paid to the importance of maintaining an apoplastic calcium concentration which permits this mechanism to operate. Data are presented for the calcicole Leontodon hispidus, in which the xylem sap may contain over 16 mM free calcium, showing that the concentration of calcium in the guard cell apoplast may be as low as 0.10 mM. This appears to be achieved by the deposition of considerable amounts of calcium oxalate in the mesophyll, particularly in the palisade tissue. Of the calcium delivered directly into the epidermis by the transpiration stream, a large proportion is diverted into the trichomes.It seems unlikely that stomatal regulation over long distances (e.g. from root to shoot) is accomplished via apoplastic calcium, but over shorter distances (the span of a few cells in the epidermis) signalling via calcium in the apoplast is entirely feasible and it is worthy of further investigation.

Guaian-5,12-olides from Leontodon hispidus

The dichloromethane extract of the whole plant of Leontodon hispidus afforded one new and two known guaian-5,12-olides. The structure of the new compound has been established by extensive 2D NMR techniques as 14-hydroxyhypocretenolide-β- d-glucopyranoside-4′-14″-hydroxyhypocretenoate.

The mycorrhizal status of plants colonizing a calamine spoil mound in southern Poland

The arbuscular mycorrhizal (AM) status of two plant communities on a calamine spoil mound (rich in cadmium, lead and zinc) in southern Poland was surveyed: an undisturbed grassland community and an early succession community that developed after complete removal of the surface layer of the calamine substrate about 10 years earlier. The undisturbed site harbored 40 herbaceous species making up 87% of the absolute cover. AM colonization was recorded in 25 species accounting for 77% of the relative cover. Species with 51–75% AM root colonization such as Festuca ovina and Leontodon hispidus dominated the undisturbed turf, contributing 45% to the relative cover. Carex ssp. were the most abundant nonmycorrhizal plants and accounted for 9% of the relative cover. Spores of Glomus aggregatum, G. constrictum, G. fasciculatum, G. pansihalos, Glomus sp. and Entrophospora sp. averaged 25 per 100 g dry substrate at the undisturbed site. The disturbed site was colonized by 25 species accounting for 17% of the absolute cover. Among the AM plants, most abundant were the species with up to 20% AM root colonization, such as Agrostis stolonifera and Thymus pulegioides, wich accounted for 24% of the relative cover. Nonmycorrhizal species, such as Biscutella laevigata,Cardaminopsis arenosa, Gypsophila fastigiata and Silene vulgaris, dominated the early succession community and contributed 64% to the relative cover. Spores of G. fasciculatum and Entrophospora sp. averaged 20 per 100 g dry substrate at the disturbed site.