''Polytrichum commune'' (also known as common haircap,
great golden maidenhair,
[ great goldilocks,][ common haircap moss, or common hair moss) is a species of ]moss
Mosses are small, non-vascular flowerless plants in the taxonomic division Bryophyta (, ) '' sensu stricto''. Bryophyta ('' sensu lato'', Schimp. 1879) may also refer to the parent group bryophytes, which comprise liverworts, mosses, and ...
found in many regions with high humidity and rainfall. The species can be exceptionally tall for a moss with stems often exceeding though rarely reaching , but it is most commonly found at shorter lengths of . It is widely distributed throughout temperate and boreal latitudes in the Northern Hemisphere and also found in Mexico
Mexico ( Spanish: México), officially the United Mexican States, is a country in the southern portion of North America. It is bordered to the north by the United States; to the south and west by the Pacific Ocean; to the southeast by Guate ...
, several Pacific Islands including New Zealand
New Zealand ( mi, Aotearoa ) is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and over 700 List of islands of New Zealand, smaller islands. It is the ...
, and also in Australia. It typically grows in bog
A bog or bogland is a wetland that accumulates peat as a deposit of dead plant materials often mosses, typically sphagnum moss. It is one of the four main types of wetlands. Other names for bogs include mire, mosses, quagmire, and muskeg; a ...
s, wet heathland
A heath () is a shrubland habitat (ecology), habitat found mainly on free-draining infertile, acidic soils and characterised by open, low-growing woody vegetation. Moorland is generally related to high-ground heaths with—especially in Great B ...
and along forest streams.
Description
''Polytrichum commune'' is a medium to large moss. It is dark green in colour, but becomes brownish with age. The stems can occur in either loose or quite dense tufts, often forming extensive colonies. The stems are most typically found at lengths of 5 to 10 cm, but can be as short as 2 cm or as long as 70 cm. They range in stiffness from erect to decumbent (i.e. reclining) and are usually unbranched, though in rare cases they may be forked. The leaves occur densely to rather distantly, and bracts are present proximally.[
The leaves typically measure 6 to 8 mm in length, but may be up to 12 mm long. When dry they are erect, but when moist they are sinuous with recurved tips and are generally spreading to broadly recurved, or sharply recurved from the base. The leaf sheath is oblong to elliptic in outline, forming an involute (i.e. with inward rolling margins) tube and clasping the stem. This sheath is typically golden yellow and shiny, and it is abruptly contracted to the narrowly lanceolate blade. Using a ]microscope
A microscope () is a laboratory instrument used to examine objects that are too small to be seen by the naked eye. Microscopy is the science of investigating small objects and structures using a microscope. Microscopic means being invisibl ...
, the marginal lamina
Lamina may refer to:
Science and technology
* Planar lamina, a two-dimensional planar closed surface with mass and density, in mathematics
* Laminar flow, (or streamline flow) occurs when a fluid flows in parallel layers, with no disruption betwe ...
can be seen to be level or erect, narrow, and typically 2 to 3 cells wide, though sometimes as many as 7 cells wide. It is toothed from the base of the blade up to the apex, with the teeth being unicellular and embedded in the margin. The costa, or central stalk of the leaf, is toothed on the underside near the apex, and is excurrent, meaning it extends beyond the end of the apex, ending in a short, rough awn
AWN may stand for:
* Awn Access to Justice Network in Gaza Strip, Legal Aid Network operate in Gaza Strip, Palestine
* Animation World Network, an online organization for animators
* Avant Window Navigator, a dock-like bar that tracks open wind ...
.[
]
The lamellae, ridges of cells that run along the leaf surface, are crenulate (i.e. with small rounded teeth) in profile and are 5 to 9 cells high. Their margins are distinctly grooved with 2 rows of paired, projecting knobs. The marginal cells, when observed in section, may be narrow, but are more typically enlarged and wider than those beneath. They are retuse (i.e. with a rounded apex with a central shallow notch) to deeply notched, and in rare cases are divided by a vertical partition. These cells are smooth and brownish in colour and have relatively thick cell walls
A cell wall is a structural layer surrounding some types of cells, just outside the cell membrane. It can be tough, flexible, and sometimes rigid. It provides the cell with both structural support and protection, and also acts as a filtering mech ...
. The sheath cells measure 60 to 90 µm
The micrometre ( international spelling as used by the International Bureau of Weights and Measures; SI symbol: μm) or micrometer (American spelling), also commonly known as a micron, is a unit of length in the International System of Unit ...
long by 10 to 13 µm wide. These cells may be elongated rectangles or strongly linear structures up to 20 times long as wide. They become narrower toward the margins. Marginal lamina cells are 10 to 15 µm wide and are subquadrate (i.e. nearly square).[
]
The plants are sexually dioicous
Dioicy () is a sexual system where archegonia and antheridia are produced on separate gametophytes. It is one of the two main sexual systems in bryophytes. Both dioicous () and monoicous gametophytes produce gametes in gametangia by mitosis ra ...
. The leaves of the perichaetium have a long sheath with a scarious (i.e. membranous) margin, while the blades themselves are greatly reduced, gradually narrowing to a finely acuminate tip. These blades have toothed margins, are denticulate to subentire in outline, roughened to almost smooth, and have a costa that is excurrent. The seta
In biology, setae (singular seta ; from the Latin word for "bristle") are any of a number of different bristle- or hair-like structures on living organisms.
Animal setae
Protostomes
Annelid setae are stiff bristles present on the body. T ...
, or capsule stalk, is 5 to 9 cm long, and is stout and yellowish to reddish brown in colour. The capsule is 3 to 6 mm long, slightly rectangular to cubic in shape, and brown to dark reddish brown in colour. It is sharply 4 winged, inclined to horizontal, and glaucous
''Glaucous'' (, ) is used to describe the pale grey or bluish-green appearance of the surfaces of some plants, as well as in the names of birds, such as the glaucous gull (''Larus hyperboreus''), glaucous-winged gull (''Larus glaucescens''), g ...
when fresh. The peristome Peristome (from the Greek ''peri'', meaning 'around' or 'about', and ''stoma'', 'mouth') is an anatomical feature that surrounds an opening to an organ or structure. Some plants, fungi, and shelled gastropods have peristomes.
In mosses
In mosses, ...
measures 250 µm, is pale in colour and has 64 teeth. The calyptra is golden yellow to brownish and completely envelops the capsule. The spore
In biology, a spore is a unit of sexual or asexual reproduction that may be adapted for dispersal and for survival, often for extended periods of time, in unfavourable conditions. Spores form part of the life cycles of many plants, algae, ...
s measure 5 to 8 µm, but may be up to 12 µm.[
]
Physiology
''Polytrichum commune'' is an endohydric moss, meaning water must be conducted from the base of the plant. While mosses are considered non-vascular plants, ''Polytrichum commune'' shows clear differentiation of water conducting tissue. One of these water conducting tissues is termed the ''hadrom'', which makes up the central cylinder of stem tissue. It consists of cells with a relatively wide diameter called ''hydroids'', which conduct water. This tissue is analogous to xylem
Xylem is one of the two types of transport tissue in vascular plants, the other being phloem. The basic function of xylem is to transport water from roots to stems and leaves, but it also transports nutrients. The word ''xylem'' is derived fr ...
in higher plants. The other tissue is called ''leptom'', which surround the hadrom and contains smaller cells. This tissue is, on the other hand, analogous to phloem
Phloem (, ) is the living tissue in vascular plants that transports the soluble organic compounds made during photosynthesis and known as ''photosynthates'', in particular the sugar sucrose, to the rest of the plant. This transport process is ...
. When these two tissue types are taken into account along with the species' exceptional height, it becomes clear that common haircap moss is quite a unique moss considering that the majority of species show little differentiation of conducting tissue and are restricted to much smaller stem lengths.
Another characteristic feature of the species (and the genus) is its parallel photosynthetic
Photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that, through cellular respiration, can later be released to fuel the organism's activities. Some of this chemical energy is stored in ...
lamellae on the upper surfaces of the leaves. Most mosses simply have a single plate of cells on the leaf surface, but common haircap moss has more highly differentiated photosynthetic tissue. This is an example of a xeromorphic adaption, an adaptation for dry conditions. Moist air is trapped in between the rows of lamellae, while the larger terminal cells act to contain moisture and protect the photosynthetic cells. This minimises water loss as relatively little tissue is directly exposed to the environment, but allows for enough gas exchange for photosynthesis to take place. The microenvironment Microenvironment may refer to:
* Microenvironment (biology), a small or relatively small usually distinctly specialized and effectively isolated biophysical environment (as of a nerve cell)
* Microenvironment (ecology), also known as a microhabit ...
between the lamellae can host a number of microscopic organisms such as parasitic fungi
A fungus (plural, : fungi or funguses) is any member of the group of Eukaryote, eukaryotic organisms that includes microorganisms such as yeasts and Mold (fungus), molds, as well as the more familiar mushrooms. These organisms are classified ...
and rotifer
The rotifers (, from the Latin , "wheel", and , "bearing"), commonly called wheel animals or wheel animalcules, make up a phylum (Rotifera ) of microscopic and near-microscopic pseudocoelomate animals.
They were first described by Rev. John H ...
s. Additionally, the leaves will curve and then twist around the stem when conditions become too dry, this being another xeromorphic adaptation. It is speculated that the teeth along the leaf's edge may aid in this process, or perhaps also that they help discourage small invertebrates from attacking the leaves.[
]
Response to herbicide exposure
In a study of the effect of the herbicide Asulam on moss growth, ''Polytrichum commune'' was shown to be the most sensitive to the herbicide out of the 18 species tested. The study concluded that it was sensitive to Asulam exposure.
Variety
* ''Polytrichum commune'' var. ''commune''
* ''Polytrichum commune'' var. ''jensenii''
* ''Polytrichum commune'' var. ''perigoniale''
References
External links
*
Profile at USDA PLANTS Database
Range Map from Flora of North America
Illustration from Flora of North America
{{Taxonbar, from=Q178025
Flora of Bulgaria
Polytrichaceae
Taxa named by Johann Hedwig