Conicum Research Articles

Light‐triggered action potentials in the liverwort Conocephalum conicum

The response to light of a liverwort, Conocephalum conicum L., measured as a change in the resting potential, consists of two stages. The first stage is a slight depolarization dependent on light intensity. This plays the role of a generator potential (GP) which induces the second stage ‐ an action potential of the all‐or‐none character. Action potentials induced by light and by electrical stimuli have the same properties, i.e. identical time course, propagation velocity, and refractory periods. A summation occurs of sub threshold light stimuli and of light and electrical stimuli. The presence of 5⋅10‐−6M DCMU cancelled the light response and blocked ‐ by inhibition of the electron transport chain ‐ the mechanism leading to GP generation. However, this effect did not produce any change in the response to electrical stimuli.

Electron microscope studies on spermatids in Conocephalum conicum by freeze-fracture replicas and ultrathin sections.

The fine structure of the spermatid in Conocephalum conicum has been studied comparatively by freeze-fracture replicas and ultrathin sections by means of transmission electron microscope. Chromatin fibrils in the nucleus offered the beaded like shape consisting of 10-25nm, granules. The distribution of the pore complexes in the nuclear envelope was localized in partly; and the intercalated particles were denser in the inner membrane of nuclear envelope. The intrastructure of cytoplasmic organelles, Golgi complex and intravacuolar vesicles have been reseached. The intravacuolar vesicles, similar to the lysosome, were examined by size and distribution of intramembrane particles in the fractured membrane.The base (the spline) of the blepharoplast was revealed as layered structure by freeze-fracturing at an oblique direction. And the mark of the filamentous appendage remained in the cell membrane. It is thought that the filamentous appendage develops along some region of the cell membrane. Freeze-fractured flagellum has the enclosed membrane intercalated by particles. The cell wall surrounding two spermatids which developed from a spermatid mother cell, consists of two layers. Its outer layer is made up of cellulose microfibrils. The septum between sister spermatids showed the microfibrillar network pattern.

The wall structure of the ‘reticulate’ cells ofConocephalum conicum(L.) Dum., observed by SEM

SEM observations on the thallus of Conocephalum conicum after treatment with sodium hypochlorite show that the walls of the ‘reticulate’ cells constituting the hyaline parenchyma have thickenings (the ‘bars’) and large primary pit fields with a huge number of plasmodesmata-derived pores, on the unthickened areas of the walls. By contrast the parenchymatous cells constituting the nerve have plasmodesmata-derived pores, grouped in small sparse fields, especially on the transverse and oblique walls. It is suggested that the reticulate cells playa role in lateral distribution by symplastic and apoplastic conduction of solutes carried by the midrib.

Species Concepts in Bryophytes: Input from Population Biology

Fortunately or not, bryophyte species concepts always have been based solely on morphological criteria. To some extent, this has been due to a lack of information regarding the population biology of mosses and liverworts. Gene flow distances, which result from sperm and spore dispersal, are extremely short, suggesting the possibility of genetic divergence between isolated colonies. Electrophoretic analyses bear out these predictions, in most cases showing unexpectedly high levels of genetic variation in these haploid-dominant organisms. Two models of genetic pop- ulation structure of bryophytes may represent ends of a continuum: (1) the Conocephalum conicum model, in which there are low levels of variation within races (which probably represent separate biological species), weak interpopulation differentiation, and no microscale heterogeneity, and (2) the Plagiomnium ciliare model, in which there are high levels of variation, strong interpopulation diferentiation, and microscale heterogeneity. Bryophyte taxonomists must decide how to use in- formation from studies of population biology, being aware of the difficulties posed by such phenom- ena as sibling species, autopolyploid species pairs, and convergent evolution. Fortunately perhaps, bryophyte species concepts always have been based solely on morphological criteria. However, the general consensus regarding how species of bryophytes should be delimited springs out of our profound ignorance of certain aspects of the basic biology of these organisms. There is limited information on reproductive isolation, gene flow, and genetic differentiation. It is, there- fore, largely unknown whether some of the vexing difficulties that have been uncovered in angiosperm taxonomy, such as sibling species, also exist in bryo- phytes. Because reproductively isolated units have been delimited so seldom in studies of bryophytes, it is impossible to state how closely such breeding groups are in accord with morphologically defined species. In this paper I shall concentrate on new ideas regarding species concepts in bryophytes and on some recently collected data. My intent is radical: to stimulate serious thinking about what a bry- ophyte species is, and what it should be, and also to point out the sorts of information we need about the basic population biology of these organisms.

The amount of polymorphism and genetic differentiation in natural populations of the haploid liverwort Conocephalum conicum.

Natural populations of diploid organisms are expected to be more polymorphic than haploid organisms under most selection models. To test this prediction and to obtain data concerning the amount of allozyme polymorphism in a haploid plant, I examined two natural populations of the haploid liverwort Conocephalum conicum by starch gel electrophoresis. Abundant genie variability was found within local populations in Japan: 7 of 11 loci. Average heterozygosity of these 11 loci was 0.167. This value is similar to those obtained for various kinds of diploid organisms. Gene identity (I) between the two populations was 0.994, and another measure of genetic differentiation, Gst was 0.018, indicating virtually no genetic differentiation between the populations. High levels of genie variability and low levels of genetic differentiation in these haploid plants are consistent with a hypothesis of selective neutrality of allozyme polymorphisms, although other possible explanations cannot be excluded.

The concentrations of lunularic acid and prelunularic acid in liverworts

The amounts of lunularic acid in suspension cultured cells of Marchantia polymorpha and thallus of Conocephalum conicum were carefully re-exami

Electrical activity of the liverwort Conocephalum conicum: The all‐or‐nothing law, strength‐duration relation, refractory periods and intracellular potentials

The characteristics of the potential changes caused by excitation of the thallus of Conocephalum conicum L. were investigated and compared with the basic criteria of an action potential. Electrical stimulation (square DC pulses) was applied, and extraand intracellular potentials were recorded. The all‐or‐nothing law, strength‐duration relation, refractory periods, and general characteristics of the changes of transmembrane potential difference were examined. The electrical phenomena occurring during the excitation of Conocephalum fulfil the basic criteria of an action potential. The results contribute additional evidence for the hypothesis that action potentials occur both in plants and in animals.

Beziehungen zwischen Atmung und Regeneration bei dem Lebermoos Conocephalum conicum (L.) Dum.

Summary In isolated thallus segments of Conocephalum conicum respiration increased continuously from the 6th to the 72th h after fragmentation. In this period a dedifferentiation of mature cells of the midribs elicited, and subsequently a new apical region was reinitiated. Together with the stimulation of respiration a dislocation of phosphates and a synthesis of substances from the ATP-type took place. However, the investigations showed that the regeneration of Conocephalum fragments is inhibited by 2,4-dinitrophenol treatment. During inhibitor treatment of fragments no synthesis of energy-rich phosphate esters was observed, but the hydrolysing activities in all parts of thallus segments increased.

Pitting of Cells in the Carpocephalum Stalk of Conocephalum conicum (L.) Dum.

In Conocephalum conicum (L.) Dum., primary pit-fields are preferentially located on the lateral walls of the cells comprising the proximal half of the stalk of the carpocephalum. In Conocephalum conicum (L.) Dum., sporangia are borne on a stalked receptacle, the whole mushroom-shaped structure being known as the carpocephalum. The initial growth of the incipient carpocephalum stalk occurs during the development of the archegonia on the carpocephalum receptacle. Following fertilization of the archegonia (in late spring) and during embryogenesis of the sporophytes, the stalk undergoes further growth by cell multiplication and cell elongation. We have designated this period of growth as the Phase One stage of stalk development. The resultant longitudinally aligned rows of parenchyma cells that are densely packed with starch grains become quiescent in the fall. In the following spring, the rapid cell-elongation growth activity of Phase Two is initiated and completed in a few days. The starch grains are digested and utilized presumably in the formation of new cell-wall carbohydrates. Functionally, the four to five centimeters of stalk elongation, due to the cell extension processes, elevate the sporangia on the receptacle-head of the carpocephalum. Once the spores are shed, the stalk (and the whole carpocephalum) becomes necrotic. Our investigation was restricted to the carpocephalum stalk in its Phase One stage of development. In this paper, we report the presence of primary pit-fields in the parenchyma cells constituting the tissue of the proximal half of the stalk. MATERIALS AND METHODS Specimens with carpocephala at the appropriate stage of development were collected from populations of Conocephalum conicum in the environs of The University of Michigan Biological Station. Immediately after a carpocephalum was dissected, its stalk was immersed in 10% Formalin buffered in 0.1 M potassium phosphate at pH 6.5 and fixed 24-48 hours. The fixed material was dehydrated in a tertiary butyl alcohol series, embedded in Bioloid paraffin (m.p. 60-62'C), and sectioned at 8 gm. Euparal provided a suitable mounting medium for phase-contrast photomicrography. OBSERVATIONS The carpocephalum stalk is composed of vertical files of parenchyma cells with a ring of small, cutinized cells at the periphery extending along the entire length of the stalk. For approximately half the length of the stalk (the proximal half), the cells possess primary pit-fields. In a longitudinal section viewed under phase-contrast optics, the pit-fields are clearly visible in surface view (Fig. I). They are preferentially located on the lateral walls. 007-2745/82/115-117$0.45/0 This content downloaded from 157.55.39.132 on Thu, 15 Sep 2016 06:12:36 UTC All use subject to http://about.jstor.org/terms 116 THE BRYOLOGIST [Volume 85

Electrical activity of the liver‐wort Conocephalum conicum.: Method of investigation and general characteristics of excitation

The excitation of the thallus of Conocephalum conicum L. produced by a tissue damaging stimulus (incision of thallus edge) was investigated. Changes in potential were measured with extracellular contact electrodes applied at various points of the thallus surface. Non‐stimulated plants showed no electrical activity. After stimulation a series of impulses occurred and were propagated all over the thallus. This plant electrical activity (PEA) depends on the magnitude of the stimulus. PEA is characterized by changes of frequency, time of duration and changes in the values of the amplitude. A similar phenomenon is well known in animal organisms as frequency coding. The general character of PEA does not depend on the kind of damaging stimulus (burn, puncture). PEA may also be induced by an electrical stimulus which does not damage the tissue.

Accumulation of 86Rb and 43K Ions in the Cells Surrounding the Air Pores of Conocephalum conicum

Summary 86Rb and 43K were introduced into the thallus of Conocephalum conicum through the rhizoids and were finally localized by microautoradiography in the cells around the air pores. Parallel experiments with T12SO4 led to massive accumulation of Tl+ in the same sites. Due to the spatial separation of the air pore apparatus from the rest of the thallus, evaporation must be strong around the pore. In accordance with the conditions of peristomatal transpiration in vascular plants, ion concentration in the apoplast around the pore must increase. As in the cells lining the pore the activity of s-glycerophosphatase was high, it was thought that carbohydrate transport must take place there, and that this process helped to pull water and ions from the apoplast into the cell.

Chirality of terpenoids isolated from the liverwort Conocephalum conicum

Reinvestigation of a Japanese sample of the thalloid liverwort Conocephalum conicum afforded (+)-bornyl ferulate and bornyl 2 - methoxy - 4 - hydroxycinnamate together with (−) - limonene, (−) - β - sabinene, (+) - bicycloelemene, (+) - β - elemene, (−) - bicyclogermacrene, lunularin, and the two compounds, 1 - octen - 3 - ol and 1 - octen - 3 - yl acetate, responsible for the mushroom-like odour of the crushed thallus. The chirality of the compounds isolated is discussed.

GEOGRAPHIC RACES OF CONOCEPHALUM (MARCHANTIALES) AS DEFINED BY FLAVONOID CHEMISTRY

SummaryAn earlier proposal that Conocephalum conicum may exist as a group of geographic races is supported by a more extensive survey of the flavonoid glycosides isolated from samples across its Northern Hemisphere distribution. European, North American, and Asian samples are clearly distinguished, and sub‐groups may be recognised within these broad subdivisions. The local Sino‐Japanese species C. supradecompositum is clearly distinguished on the basis of flavonoid glycosides from C. conicum.

Genic variabilities in natural population of haploid plant, Conocephalum conicum. I. The amount of heterozygosity.

The amount of genetic variability expected in natural populations is different for diploid and haploid organisms under most selection models: diploid organisms are expected to be more polymorphic. I examined several natural Japanese populations of haploid moss, Conocephalum conicum by starch gel electrophoresis. Seven enzyme loci out of 11 examined turned out to be polymorphic. The average heterozygosity at the 11 loci was 0.167. This value is almost identical to those obtained in diploid organisms of various sources. Moreover, abundant genic variability was found within a local population, indicating the prevalence of sexual reproduction in natural populations of this species. The equality of genic variability between diploid and haploid organisms is most easily explained by the selective neutrality of allozyme polymorphisms, though other possibilities are not excluded from the present data alone.

Genic variabilities in natural population of haploid plant, Conocephalum conicum : II. The amount of heterozygosity and the genetic differentiation

Genic variabilities in natural population of haploid plant, Conocephalum conicum : II. The amount of heterozygosity and the genetic differentiation

Fatty acid ethyl esters in the liverwort Conocephalum conicum

A series of fatty acid ethyl esters ranging from C 14 to C 24 was isolated from a hexane extract of the liverwort Conocephalum conicum, these esters accounted for 77% of the extract. The ethyl esters consisting of even-numbered fatty acids were predominant and ethyl palmitate was the major constituent.

Sesquiterpene lactones of Conocephalum conicum

Investigation of the plant growth inhibitory activity of the extract of the liverwort, Conocephalum conicum afforded five sesquiterpene lactones, tulipinolide, zaluzanin C, zaluzanin D, 8α-acetoxyzaluzanin C and 8α-acetoxy-zaluzanin D. The latter two compounds are reported for the first time. Tulipinolide is responsible for the characteristic pungency of the female gametophyte of C. conicum. The guaianolides showed inhibitory activity toward the germination and growth of roots of rice in the husk. The male gametophyte of C. conicum indicated no pungency, showing the lack of tulipinolide.

Metabolism of lunularic acid in liverworts

The presence, in Conocephalum conicum , of the enzymes phenylalanine ammonia lyase, trans -cinnamic acid-4-hydroxylase and lunularic acid decarbo

Sesquiterpenes of thalloid liverworts of the genera Conocephalum, Lunularia, Metzgeria and Riccardia

Thalloid liverworts of orders Metzgeriales and Marchantiales elaborate essential oils distinguishable from those of the Jungermanniales by the absence of β-barbatene and anastreptene. Riccardia sinuata elaborates a novel tricyclic exomethylene sesquiterpene of as yet undetermined structure. Conocephalum conicum elaborates cadinene-type sesquiterpenes. β-Cadinene from the latter species is clearly enantiomeric to the same product from vascular plants.

Saxicolous Bryophyte and Macrolichen Associations in Southern Illinois I. Little Grand Canyon, Jackson County

Saxicolous Bryophyte and Macrolichen Associations in Southern Illinois I. Little Grand Canyon, Jackson County