Rhynchostegium
Rhynchostegium is a genus of pleurocarpous mosses belonging to the family Brachytheciaceae. The genus has a cosmopolitan distribution across different climatological regions except the polar regions, mostly in tropic to north temperate regions. The genus contains both aquatic and terrestrial species. The genus was named for their rostrate opercula. The type species of this genus is Rhynchostegium confertum Schimp.
Etymology
The genus name comes from the Greek rhyncho- and stegos, which refers to the rostrate operculum of the sporophyte.
History
The genus was first described by Bruch and Wilhelm Philippe Schimper in 1852.
Habitats
Terrestrial species of Rhynchostegium live in moist to wet or shaded habitats, on rock, soil, tree base, tree stem, and logs.
Aquatic species live by or in running water, including streams, springs, rivers, beds of waterfalls, and seepy cliffs.
Morphology
Gametophyte
Rhynchostegium are small to large mosses that form either loose tuft or extensive mats on the substrate, with irregular or regular branching. The younger plants are generally deep green or light green; aging plants could become whitish, brownish, or paler green. Stems are creeping and lack hyaloderm, with acute to acuminate pseudoparaphyllia. Stem leaves are erectopatent or erect. Branch leaves are similar in morphology to stem leaves but smaller and sometimes narrower. Leaves are commonly straightly to homomallously arranged; subimbricate, subcomplanate, or complanate arrangement are sometimes seen, especially in branch leaves. Leaf base, decurrent or not, varies from ovate to ovate-cordate, occasionally lanceolate, and the narrowing from gradual to abrupt, towards a short- or long-acuminate apex, where sometimes a differentiated long acumen or apiculus is present. The leaves have a single costa that generally smoothly ends 35-75% up the leaf, and more often in branch leaves in an abaxial spine. Leaf surfaces vary from flat to slightly concave and not to strongly longitudinally plicate, with little to some pores and linear laminal cells. Leaf margins are serrate to serrulate. Axillary hairs constitute of 3-7 cells, with 1-3 upper cells. Alar cells are slightly enlarged, and either undifferentiated or quadrate to elongate-rectangular.
Sporophyte
Rhynchostegium are autoicous. Covered by a naked calyptra is a rostrate to long-rostrate operculum attached to a red-brown to brown, oblong-cylindric, weakly curved capsule, which is inclined or horizontal to a red-brown, smooth seta that has abruptly contracted perichaetial leaves at the base, with acumen straight to reflexed. An annulus separates the operculum. The peristome is xerochastic and perfect, which the red to orange-red exostomes have reduced trabeculae and cross-striolae at the base of the teeth; in rare cases the exostomes are narrow and yellow. The broadly or narrowly perforated endostomes and developed to vestigial cilia are supported by a low or high basal membrane. Spore diameters range between 9-16 μm.
Biochemistry
Allelopathy
Allelopathy has been studied on Rhynchostegium pallidifolium, which usually form pure colonies in their natural habitat. Methanol extract of R.pallidifolium represses the seedling of cress, alfalfa, lettuce, ryegrass, timothy, and Digitaria sanguinalis in a concentration-dependent manner. A combination of ESI-MS and 1H NMR analyses identified the inhibitory chemical as 3-hydroxy-β-ionone. Further study showed a minimal 3-hydroxy-β-ionone concentration of 1 μM for the inhibition of cress hypocotyl growth, and 3 μM for cress root growth, while the endogenous concentration. The presence of 3-hydroxy-β-ionone in their natural substrate and the growing medium suggested secretion to the environment, which may imply an important role of 3-hydroxy-β-ionone in competition with other plants and the forming of pure colonies.
Antibacterial
Acetone extract of Rhynchostegium riparioides showed antibiotic activity on some Gram-negative bacteria, including Escherichia coli, Proteus mirabilis, Entero-bacter cloacae and Pseudomonas ''aeruginosa.
Ethanolic extract of Rhynchostegium vagans'' showed similar effect on some Gram-negative bacteria and fungi, with performance superior to chloramphenicol and fluconazole.
Applications
Freshwater monitoring
Rhynchostegium riparioides is used in monitoring of heavy metals concentration in freshwater in multiple regions around the world, such as copper, zinc. R. riparioides as a neutrophilous species has been used in monitoring water acidification.
The World Flora Online lists 221 species of Rhynchostegium.Rhynchostegium acanthophyllum A. JaegerRhynchostegium acicula Broth.Rhynchostegium acutifolium A. JaegerRhynchostegium alboviridum R.S. WilliamsRhynchostegium algirianum Lindb.Rhynchostegium alopecuroides A.J.E. Sm.Rhynchostegium altisetum Müll. Hal.Rhynchostegium ambiguum W.R. BuckRhynchostegium anceps A. JaegerRhynchostegium aneuron Kindb.Rhynchostegium angustifolium Renauld & CardotRhynchostegium apophysatum A. JaegerRhynchostegium aquaticum A. JaegerRhynchostegium arcticum Ignatov & HuttunenRhynchostegium asperisetum A. JaegerRhynchostegium assumptionis Besch.Rhynchostegium bello-intricatum ParisRhynchostegium bequaertii Thér. & NaveauRhynchostegium berteroanum A. JaegerRhynchostegium beskeanum A. JaegerRhynchostegium bifariellum Kindb.Rhynchostegium brachypterum A. JaegerRhynchostegium brachypyxis Renauld & CardotRhynchostegium brachythecioides Dixon & P. de la VardeRhynchostegium brandegei Renauld & CardotRhynchostegium brevicuspis Müll. Hal.Rhynchostegium brevinerve Huttunen & IgnatovRhynchostegium brevirete Broth.Rhynchostegium buluense ParisRhynchostegium cacticola ParisRhynchostegium calderi VohraRhynchostegium caloosiense Renauld & CardotRhynchostegium campylocarpum De Not.Rhynchostegium campylocladulum Müll. Hal.Rhynchostegium cataractarum Thér. & P. de la VardeRhynchostegium celebicum A. JaegerRhynchostegium chrysophylloides A. JaegerRhynchostegium circinatum De Not.Rhynchostegium cirrosum De Not.Rhynchostegium collatum Broth. & WattsRhynchostegium comorae A. JaegerRhynchostegium complanum A. JaegerRhynchostegium compridense ParisRhynchostegium conchophyllum A. JaegerRhynchostegium confertum Schimp.Rhynchostegium confusum Cezón, J. Muñoz, Hedenäs & HuttunenRhynchostegium congruens Mitt.Rhynchostegium conostomus Huttunen & IgnatovRhynchostegium contortulum TixierRhynchostegium contractum CardotRhynchostegium crassinervium De Not.Rhynchostegium cylindritheca DixonRhynchostegium dasyphyllum Müll. Hal.Rhynchostegium delicatulum JamesRhynchostegium demissum Schimp.Rhynchostegium dentiferum A. JaegerRhynchostegium deplanatum Kindb.Rhynchostegium depressum Schimp.Rhynchostegium distans Besch.Rhynchostegium distratum A. JaegerRhynchostegium drepanocladioides Kindb.Rhynchostegium duthiei Müll. Hal. ex DixonRhynchostegium elusum A. JaegerRhynchostegium erythropodium Mitt.Rhynchostegium esquirolii Cardot & Thér.Rhynchostegium exiguum Brockm.Rhynchostegium exilissimum A. JaegerRhynchostegium fabroniadelphus A. JaegerRhynchostegium fauriei CardotRhynchostegium finitimum ÅngströmRhynchostegium fissidens Kindb.Rhynchostegium fissidentellum Besch.Rhynchostegium fragilicuspis DixonRhynchostegium fuegianum Huttunen & IgnatovRhynchostegium funckii De Not.Rhynchostegium gaudichaudii A. JaegerRhynchostegium georgianum Dixon & GroutRhynchostegium glaucovirescens Kindb.Rhynchostegium globipyxis Kindb.Rhynchostegium gracilipes Thér.Rhynchostegium graminicolor A.L. AndrewsRhynchostegium herbaceum A. JaegerRhynchostegium hians DelogneRhynchostegium homaliocaulon Kindb.Rhynchostegium hookeri A. JaegerRhynchostegium hopfferi A. GeppRhynchostegium horridum Broth.Rhynchostegium huitomalconum Besch.Rhynchostegium humillimum A. JaegerRhynchostegium hunanense Ignatov & HuttunenRhynchostegium huttonii ParisRhynchostegium illecebrum DelogneRhynchostegium inaequale DixonRhynchostegium inclinatum A. JaegerRhynchostegium inerme A. JaegerRhynchostegium irriguum DixonRhynchostegium isopterygioides CardotRhynchostegium jamesii Sull.Rhynchostegium javanicum Besch.Rhynchostegium jovet-astiae BizotRhynchostegium laevisetum Mitt.Rhynchostegium lamasicum Besch.Rhynchostegium laxatum ParisRhynchostegium laxirete Broth.Rhynchostegium leptoblastum Kindb.Rhynchostegium leptomerocarpum Besch.Rhynchostegium leptopteridium Müll. Hal.Rhynchostegium leucodictyon Müll. Hal.Rhynchostegium lindmanii ParisRhynchostegium lusitanicum Broth.Rhynchostegium luteonitens A. JaegerRhynchostegium mac-owanianum ParisRhynchostegium malmei ParisRhynchostegium megapolitanum Schimp.Rhynchostegium membranaceum Broth.Rhynchostegium menadense A. JaegerRhynchostegium meridionale De Not.Rhynchostegium micans AustinRhynchostegium microthamnioides Müll. Hal.Rhynchostegium minutum Müll. Hal.Rhynchostegium muelleri A. JaegerRhynchostegium murale Schimp.Rhynchostegium muriculatum ReichardtRhynchostegium mutatum Huttunen & IgnatovRhynchostegium myosuroides De Not.Rhynchostegium nanopennatum Kindb.Rhynchostegium nanothecium Müll. Hal. ex DixonRhynchostegium nervosum Broth. ex CardotRhynchostegium nigrescens Besch.Rhynchostegium oblongifolium Broth. & WattsRhynchostegium obtusatum Broth.Rhynchostegium obtusifolium A. JaegerRhynchostegium occultum Larraín, Huttunen, Ignatova & IgnatovRhynchostegium omocrates W.R. BuckRhynchostegium ovalfolium S. OkamuraRhynchostegium oxyodon A. GeppRhynchostegium pallidifolium A. JaegerRhynchostegium pallidius A. JaegerRhynchostegium pampae Kindb.Rhynchostegium parvulum Broth.Rhynchostegium patulifolium Cardot & Thér.Rhynchostegium patulum A. JaegerRhynchostegium pectinatum ParisRhynchostegium pellucidum DixonRhynchostegium pendulum A. JaegerRhynchostegium peruviense OchyraRhynchostegium pervilleanum A. JaegerRhynchostegium philippinense A. JaegerRhynchostegium piliferum De Not.Rhynchostegium pinnicaule Kindb.Rhynchostegium plagiotheciella Müll. Hal.Rhynchostegium planifolium Müll. Hal.Rhynchostegium planiusculum A. JaegerRhynchostegium praecox De Not.Rhynchostegium praelongum De Not.Rhynchostegium pringlei CardotRhynchostegium pseudoconfertum A. JaegerRhynchostegium pseudodistans CardotRhynchostegium pseudomurale A. JaegerRhynchostegium pseudoserrulatum Kindb.Rhynchostegium psilopodium Ignatov & HuttunenRhynchostegium pulchellum H. Rob.Rhynchostegium pumilum De Not.Rhynchostegium raphidorrhynchum A. JaegerRhynchostegium recurvans Besch.Rhynchostegium revelstokense Kindb.Rhynchostegium riparioides CardotRhynchostegium rivale A. JaegerRhynchostegium robustum W.R. BuckRhynchostegium rotundifolium Schimp.Rhynchostegium royae Renauld & CardotRhynchostegium ruvenzorense ParisRhynchostegium santaiense Broth.Rhynchostegium sarcoblastum Broth. & ParisRhynchostegium savatieri ParisRhynchostegium scariosum A. JaegerRhynchostegium selaginellifolium Müll. Hal.Rhynchostegium sellowii A. JaegerRhynchostegium semiscabrum H. Rob.Rhynchostegium semitortulum Kindb.Rhynchostegium semitortum A. JaegerRhynchostegium senodictyon A. JaegerRhynchostegium serpenticaule Broth.Rhynchostegium serrulatum A. JaegerRhynchostegium shawii Hutsemekers & Vanderp.Rhynchostegium sinense Broth.Rhynchostegium sparsirameum ParisRhynchostegium stokesii De Not.Rhynchostegium stramineoides Wijk & Margad.Rhynchostegium striatum De Not.Rhynchostegium strigosum De Not.Rhynchostegium strongylense W.R. Buck & PriviteraRhynchostegium styriacum Kindb.Rhynchostegium subacutifolium A. JaegerRhynchostegium subbrachypterum Broth. & BryhnRhynchostegium subclavatum A. JaegerRhynchostegium subconfertum A. JaegerRhynchostegium subenerve A. JaegerRhynchostegium submenadense Thér. & P. de la VardeRhynchostegium subperspicuum Broth.Rhynchostegium subrectocarpum VohraRhynchostegium subrotundum A. JaegerRhynchostegium subrusciforme A. JaegerRhynchostegium subserrulatum A. JaegerRhynchostegium subspeciosum Müll. Hal.Rhynchostegium subtrachypterum Bryhn ex P. Syd.Rhynchostegium surrectum A. JaegerRhynchostegium taphrophilum Müll. Hal.Rhynchostegium tenellum Schimp.Rhynchostegium tenuifolium ReichardtRhynchostegium tenuivagum ParisRhynchostegium tocaremae A. JaegerRhynchostegium trachynotum Kindb.Rhynchostegium trachypelma A. JaegerRhynchostegium trieblingii Müll. Hal.Rhynchostegium tubaronense Müll. Hal.Rhynchostegium ulicon A. JaegerRhynchostegium validum OchyraRhynchostegium vitianum E.B. Bartram & DixonRhynchostegium volkensii ParisRhynchostegium vriesei A. JaegerRhynchostegium zeyheri A. Jaeger