Conicum Research Articles

Effects of quercetin and verapamil on membrane potential in the liverwort Conocephalum conicum

Quercetin is a very common flavonoid widely distributed in many plants. The flavonoid intake has been linked to the prevention of human diseases including cancer. Flavonoids possess also a broad spectrum of effects on plants. Quercetin is involved in Ca2+ transport and metabolism. The present study was designed to check the effects of quercetin alone and in combination with verapamil on the resting and action potentials in the liverwort Conocephalum conicum. The application of 59·10−6 mol·dm−3 quercetin caused an increase of action potential amplitudes. During the 3rd and 4th hour of treatment an increase by 20–22 % with respect to the control was observed. No changes were found in the resting potential in quercetin treated plants. Verapamil, a calcium channel inhibitor, caused gradual decrease of action potential amplitudes. Quercetin, when added together with verapamil, prevented its inhibitory effect. Interactions between quercetin and Ca2+ transport are discussed.

苔類ジャゴケ及びフジウロコゴケの植物化学的研究

Four hundred samples of Conocephalum conicum, collected in various places have been analyzed by GC-MS. This resulted in the presence of three chemo-types of C. conicum. One of them elaborate (-)-sabinene (type-I) as a major compound. The other two types characteristically contained (+)-bornyl acetate (type-II) and methyl cinnamate (type-III) as major constituent respectively. The structures of three new monoterpenic esters, isolated from the ether extract of C. conicum (type-I and/or II) have been established by chemical and spectral means. They were shown to be monoterpenic esters of (+)-borneol and p-coumaric acid derivatives. The ether extract of the liverwort Chiloscyphus polyanthos afforded sesquiterpenoids which are enantiomeric to those found in another liverwort Lepidozia vitrea. The absolute configurations of the sesquiterpenoids found in the C. polyanthos were determined by spectroscopic evidence, chemical derivatization and/or x-ray crystallographic analysis. The ether extract of the liverwort Porella perrottetiana afforded (-)-alpha-eudesmol, which showed an opposite sign of the optical rotation to that found in higher plants. Present work on the absolute configuration and an optical purity of (-)-alpha-eudesmol strongly suggested that the positive values (e.g. +28.5 degrees) described in many previous papers should be revised. Since the absolute configuration of (-)-alpha-eudesmol was identical to that (+)-beta-eudesmol found in the higher plants, it was apparent that the expression of the positive sign might be revised to (-)-alpha-eudesmol. The optical purity, reconfirmation of the absolute configuration and synthesis of (-)-alpha-eudesmol will be discussed.

INDIRECT FACILITATION: EVIDENCE AND PREDICTIONS FROM A RIPARIAN COMMUNITY

Indirect facilitation occurs when the indirect positive effect of one species on another, via the suppression of a shared competitor, is stronger than the direct competitive effect. Although theory predicts that these interactions may be common in assemblages of three or more competitors, experimental studies of this process are rare. Here, I report a study of a northern California riparian community, where I tested the hypothesis that the sedge Carex nudata had direct competitive effects on other plant species, as well as indirect facilitative effects, by suppressing a second competitor, the common monkey-flower Mimulus guttatus. Results of a field experiment, in which I manipulated the presence of Carex and M. guttatus in a factorial design, uncovered three qualitatively different interactions between Carex and three target species. I found evidence of indirect facilitation for the liverwort Conocephalum conicum, such that Carex “facilitated” Conocephalum in the presence of M. guttatus, while Carex competed with Conocephalum in the absence of M. guttatus. Plant distribution patterns supported the widespread occurrence of this interaction. Carex also had an indirect positive effect on the scarlet monkey-flower M. cardinalis, though the magnitude of this effect was similar to direct Carex competition. Lastly, Carex had no influence on the moss Brachythecium frigidum. The mechanisms underlying the plant interactions in this study are discussed and incorporated into a general hypothesis that indirect facilitation among competitors is most important in assemblages of species that vary in competitive mechanism.

Indirect Facilitation: Evidence and Predictions from a Riparian Community

Indirect facilitation occurs when the indirect positive effect of one species on another, via the suppression of a shared competitor, is stronger than the direct competitive effect. Although theory predicts that these interactions may be common in assemblages of three or more competitors, experimental studies of this process are rare. Here, I report a study of a northern California riparian community, where I tested the hypothesis that the sedge Carex nudata had direct competitive effects on other plant species, as well as indirect facilitative effects, by suppressing a second competitor, the common monkey-flower Mimulus guttatus. Results of a field experiment, in which I manipulated the presence of Carex and M. guttatus in a factorial design, uncovered three qualitatively different interactions between Carex and three target species. I found evidence of indirect facilitation for the liverwort Conocephalum conicum, such that Carex “facilitated” Conocephalum in the presence of M. guttatus, while Carex competed with Conocephalum in the absence of M. guttatus. Plant distribution patterns supported the widespread occurrence of this interaction. Carex also had an indirect positive effect on the scarlet monkey-flower M. cardinalis, though the magnitude of this effect was similar to direct Carex competition. Lastly, Carex had no influence on the moss Brachythecium frigidum. The mechanisms underlying the plant interactions in this study are discussed and incorporated into a general hypothesis that indirect facilitation among competitors is most important in assemblages of species that vary in competitive mechanism.

Sesquiterpenes from the essential oil of the liverwort Conocephalum conicum

Abstract Three new brasilane type sesquiterpenes related to the known alcohol conocephalenol and the sesquiterpene alcohol presilphiperfolan-1-ol were isolated from a chemotype of the liverwort Conocephalum conicum collected in southern Germany and identified by NMR investigations, enantioselective gas chromatography and chemical correlations. In addition ent -(−)-dactylol, the enantiomer of a compound so far only found as a constituent of the Caribbean sea hare Aplysia dactylomela , was identified.

Two aromadendrane type alcohols from the liverwort Conocephalum conicum

Abstract (−)-Aromadendran-5-ol and (+)-aromadendr-4-en-12-ol were isolated from the essential oil of a chemotype of Conocephalum conicum . The structures of the compounds were derived by NMR investigations and by conversion of the compounds into a series of products of known configuration by hydrogenation and dehydration.

Studies of Specialized Pitted Parenchyma Cells of the Liverwort Conocephalum Hill and Their Phylogenetic Implications

Except for a few members of the Metzgeriidae, occurrences of specialized conducting tissues are undocumented in liverworts. There have been reports, however, that some liverworts, including the complex thalloid liverwort Conocephalum Hill, possess strands of elongate cells with variously thickened and/or pitted walls. In Conocephalum these specialized cells are ornamented with unpigmented anastomosing bands and have many circular, pit‐like structures in their walls. SEM studies show that the anastomosing striae are visible only on inner wall surfaces. In Conocephalum japonicum (Thunb.) Grolle, many circular, thin‐walled pits are scattered on the lateral walls. Conocephalum conicum (L.) Dumort. may occasionally perforate at the pits to form open pores between cells. TEM micrographs verify that the reticulations of Conocephalum are deposited as primary wall thickenings to the inside of the middle lamella. Primary pit fields are formed on both lateral walls and end walls in C. conicum but are found on lateral walls only in C. japonicum. Many plasmodesmata and desmotubules are observed in the primary pit fields. Histochemical studies demonstrate that the wall thickenings are nonlignified cellulose deposits and that callose is absent from the primary pit fields. The nucleus remains in some of the specialized pitted cells but is absent in others. Positive acid phosphatase activity, which indicates the occurrence of some protoplasmic hydrolysis, is found in some of the specialized cells, which are scattered through both younger and older thallus tissues. Studies of water‐conducting potential demonstrate that, while the specialized pitted cells in the vegetative thalli and archegoniophores of Conocephalum do not form a continuous water‐conducting strand, they do facilitate absorption of water from the rhizoids into the thallus and archegoniophore, respectively. These specialized pitted cells of Conocephalum are not directly homologous to metzgerialean water‐conducting cells, moss hydroids and leptoids, or G‐type and S‐type water‐conducting cells of early fossil land plants, although there are some shared characters with each of these cell types.

Genetic differentiation within sibling species of Conocephalum conicum (Marchantiales: Hepaticae) in East Asia

Genetic differentiation within sibling species of Conocephalum conicum (Marchantiales: Hepaticae) in East Asia

Calcium-Dependent Voltage Transients Evoked by Illumination in the Liverwort Conocephalum conicum

The liverwort Conocephalum conicum with anion channels blocked by anthracene-9- carboxylic acid (A-9-C) and potassium channels blocked by tetraethylamm onium (TEA) generates dose-dependent responses to illumination further called voltage transients (VTs). Unlike the action potentials in untreated Conocephalum thalli, VTs do not propagate and cannot be evoked by electrical stimuli. Except A-9-C, two other anion channel inhibitors: ethacrinic and niflumic acids were effective in inducing VTs. These responses were blocked by DCMU, diethylstilbestrol and vanadate, which indicates that the photosynthetic electron transfer chain and the proton pump mediate in their generation. Light-induced VTs were considerably suppressed by calcium channel inhibitors: Mn2+, Gd3+, verapamil and nifedipine, and to a less extent by La 3+ and diltiazem, provided that the incubation lasted more than 2 h. The participation of voltage-indep endent Ca2+-permeable channels in ionic mechanism of VTs is postulated.

Water relations, chlorophyll fluorescence, and membrane permeability during desiccation in bryophytes from xeric, mesic, and hydric environments

The interactions among water content, chlorophyll a fluorescence emission, and potassium leakage were analyzed during dehydration in desiccation-tolerant bryophytes from xeric habitats (Hedwigia ciliata (Hedw.) P. Beauv., Hypnum cupressiforme Hedw., Leucodon sciuroides (Hedw.) Schwaegr., Orthotrichum cupulatum Brid., Pleurochaete squarrosa (Brid.) Lindb., Porella platyphylla (L.) Pfeiff., and Tortula ruralis (Hedw.) Gaertn., Meyer & Scherb.) and desiccation-intolerant bryophytes from mesic and hydric environments (Barbula ehrenbergii (Lor.) Fleisch., Cinclidotus aquaticus (Hedw.) B. & S., Conocephalum conicum (L.) Underw., Lunularia cruciata (L.) Dum. ex Lindb., Palustriella commutata (Hedw.) Ochyra, Philonotis calcarea (B. & S.) Schimp., and Rhynchostegium riparioides (Hedw.) Card.). Their fluorescence characteristics at low water content were low efficiency of photosynthetic quantum conversion, closed photosystem II reaction centers, and strong nonphotochemical quenching only in desiccation-tolerant species. Full restoration of fluorescence parameters upon rewatering in species from xeric environments indicated that the photosynthetic apparatus was fully functional after desiccation. Species from hydric and mesic habitats were unable to restore photochemical activity. This might be a consequence of photoinhibition but also of membrane damage, as indicated by the large leakage of potassium. It is suggested that the capacity to enhance thermal energy dissipation during dehydration might have evolved in species from xeric environments as an adaptation to the utilization of an erratic supply of water. This protective strategy would lower the probability of photodamage during water loss and thus maintain the photosynthetic apparatus in a quickly recuperable state.Key words: bryophytes, chlorophyll fluorescence, dehydration, desiccation tolerance, thermal energy dissipation.

Water-content components in bryophytes: analysis of pressure-volume relationships

The water associated with a bryophyte can be divided into (a) apoplast water held in cell-wall capillary spaces and by matric forces, (b) osmotic (symplast) water, and (c) external capillary water. In many bryophytes (c) is a large and variable component, preventing easy determination of full-turgor water content and of relative water content (RWC) values physiologically comparable with those for vascular-plant leaves. Pressurevolume (P-V) curves are presented and water-relations parameters estimated for bryophytes, including species with large thin-walled cells (Hookeria lucens and three marchantialian thalloid liverworts), species with notably thick cell walls (Neckera crispa), and species with wettable surfaces and well-developed external capillary water conduction (Tortula ruralis, Anomodon viticulosus), and for the lichen Cladonia convoluta. Full-turgor water content ranged from c. 110% DW. in T. ruralis and Andreaea alpina to 1400% DW. or more in Dumortiera hirsuta and Conocephalum conicum. Osmotic potential (Ψπ) at full turgor was between −1.0 and −2.0 MPa in most species, but substantially less negative values were found in the thalloid liverworts (−0.35 to −0.64 MPa). The x-intercept of the P-V curve is not a reliable estimate of apoplast volume and may give negative values; better estimates of apoplast volume may be obtained by vapour equilibration at known low water potentials. Blotting external water from shoots usually gave fullturgor water content estimates in reasonable agreement with those obtained by analysis of P-V curves, but for different reasons they could be either higher or lower than the true value. The importance of know ing full-turgor water content for physiological work on water-stress responses in bryophytes is emphasized.

Monoterpene Biosynthesis in the Liverwort Conocephalum Conicum: Demonstration of Sabinene Synthase and Bornyl Diphosphate Synthase in Honour of Professor G. H. Neil Towers 75th Birthday

(−)-Sabinene is the major monoterpene produced by a European strain of the liverwort Conocephalum conicum. A cell-free extract from in vitro cultured plants catalysed the cyclization of geranyl diphosphate to sabinene. The responsible monoterpene cyclase was partially purified and characterized as an operationally soluble enzyme of Mr 65 000, with a pH optimum at 7.5 and a requirement for a divalent metal ion as the only cofactor, with Mg2 preferred. The general properties of the sabinene synthase from C. conicum resemble those of other monoterpene cyclases from gymnosperms and angiosperms. A North American strain of the liverwort produces (+)-bornyl acetate as the major monoterpene and it was demonstrated that bornane-type monoterpenes are derived from geranyl diphosphate in this liverwort, as in higher plants, by the action of bornyl diphosphate synthase.

Bioindication of heavy metals in soil by liverworts.

Studies were made of the accumulation of the heavy metals Ba, Cd, Co, Cr, Cu, Fe, Hg, Ni, Pb, Sr, V, and Zn and the macroelements N, P, K, Ca, and Mg in liverworts Conocephalum conicum, Marchantia polymorphia, and Pellia epiphylla collected from 57 microhabitats in Poland (Lower Silesia, Tatry Mts., and Puszcza Augustowska forest) and one microhabitat in the Czech Republic (Moravsky Kras). Ecological differentiation of Conocephalum conicum, Marchantia polymorpha and Pellia epiphylla populations is closely correlated with the soil chemistry. The evidence for this assumption are the significant positive correlations between concentrations of elements in soil and in the examined liverworts. In particular, correlations between contents of chromium and cobalt in soil and in Conocephalum conicum and between nickel, chromium, copper, and barium in soil and in Pellia epiphylla prove that these plants can be useful in monitoring of contamination of soil with elements mentioned above. Concentrations of cobalt in almost all the examined liverworts surpass the average background values of this element established for terrestrial bryophytes what proves that these plants tolerate increased accumulated amounts of this element and may therefore act as bioindicator for this heavy metal. Cationic equilibrium of Conocephalum conicum, Marchantia polymorpha and Pellia epiphylla examined according to Czarnowski (1977) pointed to the existence of some disturbances in ionic balance of these plants caused probably by elevated concentrations of microelements (especially iron, cobalt, lead, and copper) in their tissues.

A comparative study on three chemo-types of the liverwort Conocephalum conicum using volatile constituents

GC-mass spectrometric analysis of 280 samples of Conocephalum conicum, collected in various places showed the presence of three chemo-types. One elaborated (−)-sabinene (type I) as the major compound the second produced (+)-bornyl acetate (type II) and the third contained methyl cinnamate (type III) as the major constituent. The structures of three new monoterpenic esters were established by chemical and spectral means.

Natural occurrence of both enantiomers of cadina-3,5-diene and δ-amorphene

The labile sesquiterpene hydrocarbon (−)-(1 R,7 S,10 R)-cadina-3,5-diene was isolated from manuka oil ( Leptospermum scoparium) by preparative gas chromatography, while its enantiomer is present in a chemotype of the liverwort Conocephalum conicum collected in southern Germany. The structure and absolute configuration was derived by NMR investigations, enantioselective gas chromatography and by conversion into a series of products of known stereochemistry by acid catalysed rearrangement, e.g. (−)-(7 S,10 R)- trans-calamenene, (−)-(7 S,10 R)-cadina-1(6),4,diene, (−)-(1 R,7 S,10 R)-bicyclosesquiphellandrene and (−)-(1 R,10 R)-zonarene. In addition, (+)-δ-amorphene was identified as a constituent of L. scoparium, while (−)-δ-amorphene is present in vetiver oil. Both enantiomers of this sesquiterpene, which has not been described as a natural product so far, were prepared by rearrangement of an enantiomeric mixture of germacrene D isolated from Solidago canadensis.

DEGRADATION AND RELEASE FROM THE THYLAKOID MEMBRANE OF PHOTOSYSTEM II SUBUNITS AFTER UV-B IRRADATION OF THE LIVERWORT CONOCEPHALUM CONICUM

The effect of ultraviolet-B (UV-B) radiation on the amount of various Photosystem (PS) II subunits has been studied in the thalloid liverwort Conocephalum conicum. UV-B irradiation led to a drastic decrease of the reaction center proteins D1 and D2 and the outer light harvesting antenna (LHC II). A minor reduction was found in the levels of the CP 43 polypeptide of the inner antenna and the 33, 23 and 16 kDa extrinsic polypeptides of PS II. During UV-B irradiation, the extrinsic polypeptides accumulated in the soluble protein fraction, but D1 and D2 were not dedectable. Streptomycin, but not cycloheximide inhibited the repair process of PS II, indicating that only protein synthesis in the chloroplast is necessary for recovery. This indicates that the extrinsic proteins of PS II dissociate from the membrane during UV-B treatment and reassociate with PS II in the course of the repair process. We conclude that the reaction center core is a target of UV-B radiation in C. concicum. The extrinsic proteins of PS II are not directly affected by UV-B, but their release is the consequence of UV-B-induced degradation of the D1 and D2 proteins.

Effects of Anion Channel Inhibitors on Light-Induced Potential Changes in the Liverwort Conocephalum conicum

The effect of three different anion channel inhibitors, namely (5-nitro-2-3-phenylpropyl-amino)benzoic acid (NPPB), Zn 2+ and anthracene-9-carboxylic acid (A-9-C) on the action potential in the liverwort Conocephalum conicum were tested. All three caused an increase of the excitability threshold and a decrease of action potential amplitudes. This confirms the involvement of anion channels in the action potentials in Conocephalum. In plants treated with 1 or 2 mM A-9-C but not with NPPB (50 or 100 //M) and Zn 2+ (100 or 500 //M), a light-induced transient depolarization occurred. In contrast to action potentials, the amplitude of this voltage transient depended on the light intensity and on the duration of preceding dark period. Also in contrast to action potentials, which are blocked by TEA, when applied together with A-9-C, TEA even increased the amplitudes of the light-induced voltage transients to up to 170 mV. The depolarization was obviously limited by the voltage-dependent opening of K + channels in the absence of TEA. The amplitude of the light-induced voltage transients (in the presence of TEA) increased in elevated CaCI2 concentrations pointing to a Ca 2+ permeability giving rise to the depolarization. However, none of the Ca 2+ channel blockers tested, La 3+ , Gd 3+ , nifedipine, verapamil or diltiazem, had an effect. The light-induced voltage transients in A-9-C treated plants are quite different from light- and electrically triggered action potentials but share some similarities with light-induced generator potentials.

Mnium orientale sp. nov. from Japan Is Morphologically and Genetically Distinct from M. hornum in Europe and North America

Mnium orientale sp. nov. from Japan Is Morphologically and Genetically Distinct from M. hornum in Europe and North America

A phenethyl glycoside from Conocephalum conicum

The chemical constituents of the Japanese liverwort, Conocephalum conicum, belonging to chemotype I, have been investigated and 2-(3,4-dihydroxypheny)ethyl-β-allopyranoside has been isolated from the methanol extract.

Inhibition of Photosystem II by UV‐B Radiation and the Conditions for Recovery in the Liverwort Conocephalum conicum Dum.

Abstract:Inhibition of photosynthesis by UV‐B was investigated in the thalloid liverwort Conocephalum conicum Dum. UV‐B irradiance was adjusted to a strength producing 50% inhibition of the rate of photosynthesis during 10 min of irradiation. A linear relationship of the fluorescence terms Fv/Fm of photosystem (PS) II and JP was observed following a UV‐B irradiation. This suggested that PS II was a major site of UV‐B‐induced damage of photosynthesis. The apparent inhibition of Fv/Fm was much smaller when electron flow to the secondary PS II acceptor QB was inhibited by DCMU or when Fv/Fm was measured at 77 K. Apparently, the major target of UV‐B effects was electron donation to the PS II reaction center, rather than electron transfer reactions at the PS II acceptor side. The time required for repair of PS II from UV‐B‐induced damage was light‐dependent and minimal at a flux density of 5 μE m−2 s−1. Low temperatures and the presence of streptomycin inhibited the repair processes of PS II, indicating that protein synthesis may be involved in the recovery of PS II. The data indicate that UV‐B irradiation on bright and cool winter days may be most harmful for photosynthesis of C. conicum. A repeated irradiation of the thalli with UV‐B induced tolerance of photosynthesis which was related to an accumulation of pigments with a maximum of absorption around 315 nm.