Do Bryophytes Have True Roots

Calypogeia trichomanis : Hahn illustration

What is a bryophyte ?

If you lot read no more than this page, yous will have a very basic, but adept, agreement of the nature and ecology of bryophytes. Much of the residue of the website consists of expansions of the topics presented here and you tin can go to many of those expansions past clicking on the embedded links.

The word bryophyte is the collective term for mosses, hornworts and liverworts and bryology is the report of bryophytes. While there are marked differences betwixt these iii groups of organisms, they are related closely enough to warrant a single term that includes all iii. So a moss is a bryophyte, a liverwort is a bryophyte and a hornwort is a bryophyte.

These are all plants, scientifically classified within the Constitute Kingdom. They are spore-producing, rather than seed-producing, plants and they are all without flowers. Like any living organisms bryophytes are classified hierarchically. Related species are grouped into genera, related genera are grouped into families and so on. That topic is the subject of the Nomenclature page.

In a moss plant you'll find leaves growing from stems and in many moss species yous will at times encounter solid-stalked spore capsules growing out from the leafy part of the constitute. In other species the spore capsule will be stalkless. Hornworts are not leafy. The main part of the plant consists of a light-green, flattish sail - which may exist lobed or somewhat wrinkled. This sail-like course is called a thallose growth habit. In hornworts the spore capsules are thin, tapering "horns" or needles that abound out from the thallose part. Here is a hornwort with a few immature capsules growing upwards from the thallose base. This photo shows a hornwort colony with numerous immature but more advanced capsules and here are mature capsules, now brown in their upper parts. Liverworts come in two growth forms, with both thallose species and leafy species - with the latter having leaves on stems, just like mosses. Spore capsules are produced in various ways. In the thallose liverwort genus Riccia the capsules are embedded in the thallose sheet and in the picture (below correct) you can see a couple of empty cavities within the thallose growth. Those are spore capsules which accept opened and from which almost of the spores have been dispersed.. In leafy liverworts and a number of thallose liverworts the capsules are atop stalks.

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Colony of the moss Bryum sp.

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Riccia sp., a liverwort

Many people are familiar with the thallose liverwort species Lunularia cruciata. It tin can form large colonies in glasshouses and in flower pots. However, while a few of the thallose liverwort species are quite conspicuous, there are far more leafy species than there are thallose species of liverworts.

In mosses and leafy liverworts the leaves are fairly pocket-sized and in some cases the stems can be quite short as well. For more than details about the construction of bryophytes go to the BRYOPHYTE GROUPS SECTION. That department is devoted to explaining what you run across when you expect at a moss, liverwort or hornwort. At that place you lot'll find out about the features you tin run into with the naked eye as well as some of the finer detail that a micoscope reveals.

Afterward a cursory discussion well-nigh "mossy things", this section will continue with some basic facts about bryophytes in general and a brief account of the varied ecological roles they play.

Mossy things

Many people accept some familiarity with "mossy things". They've seen "mossy things" growing in their gardens, in cracks in footpaths (or even on footpaths), on tree trunks in parks and on boulders in the bush-league. To many people, anything smallish and light-green is labelled a "moss". Only is that sort of labelling correct? Certainly, many minor, greenish organisms are mosses, but...

...non all "mossy things" are mosses !

In that location are various pocket-sized, light-green organisms that are non mosses. In fact, the green-leaved plant shown in the painting at the top of this page is a leafy liverwort. Conversely, mosses aren't always small and they aren't always green.

Yous could expect that many people think of the closely related liverworts and hornworts equally mosses. That certainly happens merely, from the descriptions given higher up, hornworts and thallose liverworts are clearly quite different to mosses. However, leafy liverworts are plain very similar to mosses, since they both have leaves on stems. Moreover, there are a few species of leafy liverworts that can exist quite common in suburban gardens and then that in many cases the leafy, "mossy" plants that people see are in fact leafy liverworts rather than mosses. How practice yous tell them apart? And if you take a thallose bryophyte, how practice yous know whether it's a hornwort or a thallose liverwort? Some earlier links gave detailed descriptions of the separate bryophytes and there'southward a summary of much of that information that allow'due south yous answer the question: WHICH BRYOPHYTE IS IT?

Still, in that location are other organisms, not at all closely related to bryophytes, but which (to many people) take a "greenish, mossy await". Examples of these are various algae, lichens, filmy ferns and the smaller fern allies, such as the genus Selaginella. There are also some organisms which include the discussion "moss" in their common names but which are non mosses. A well known case is Spanish Moss - which is a flowering plant. You can discover out more in the section that deals with WHAT'S Non A BRYOPHYTE.

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Gigaspermum repens, a moss

Getting dorsum to mosses, on the correct is a photograph of Gigaspermum repens, a moss with white leaves. At that place'southward a lot of red in this photograph of a colony of the moss Polytrichum juniperinum - but they aren't red flowers, they're leaves. Mosses don't take flowers. Not to be outdone in colour variety here are ii thallose liverworts, the green and white Riccia crystallina and the crimson-margined Riccia cavernosa . Here's a photo of the moss Papillaria flavolimbata, which tin grow in extensive defunction. It's certainly not small.

This already indicates that there's a lot more to mossy things than outset meets the middle.

Bryophytes - some basic facts

Virtually all bryophytes incorporate chlorophyll and then make their ain food from water and carbon dioxide, via photosynthesis. There is i liverwort (Cryptothallus) which lacks chlorophyll and relies on a fungal partner for food.

Bryophytes vary in size from plants only slightly over a millimetre tall to trailing species which abound to strands well over a metre long. A common misconception is that to discover bryophytes you need to be in a damp, shaded streamside – preferably non in summer. In fact bryophytes can be found in great diversity throughout the twelvemonth in areas ranging from arid to rainforest, and in habitat from ocean-level to alpine. They occur most abundantly in relatively unpolluted areas. Some species take specific habitat preferences while others are found in a variety of habitats. They can be found growing on all sorts of surfaces (or substrates) - soil, rock, tree trunks, leaves, rotting wood, basic, sometime discarded shoes or gloves – to proper noun a few possibilities. Bryophytes don't have true roots. They have root-similar anchoring structures, called rhizoids , only these (dissimilar the roots of nigh plants) do non actively extract minerals and water from the substrate.

Bryophytes and H2o

A corking many bryophytes are able to survive dormant during periods of extreme dryness or extreme cold and the species living in harsh environments have diverse survival mechanisms. Many moss species in such areas grow absorber-like , each cushion being a dense colony of private plants. In this manner most of the colony is protected from the directly effect of the harsh atmospheric condition. Many arid surface area bryophytes curlicue upward in various means to reduce their exposed surface areas. In various species the chlorophyll undergoes a change in structure in order to survive the dry periods undamaged. You'll find natural anti-freeze in various common cold-area bryophytes.

Dormant bryophytes tin can become agile with just a footling water. It need non even be rain - fog or dew will exist enough in many cases. This is why you can detect bryophytes in deserts where rainfall may be very rare. In such areas the nights can still get cold, resulting in early morning dew formation - plenty to bring the bryophytes out of dormancy. They tin then photosynthesize for perhaps a few hours before the heat of the day forces them back into dormancy.

Most bryophytes absorb water and dissolved minerals over their surfaces - for example, through the leaf surfaces in many mosses and leafy liverworts. In cases such every bit this the captivated h2o and minerals are immediately available in the places where photosynthesis occurs. Many bryophytes have various structural features which assist external water conduction. For example, overlapping leaves on stems; rhizoids with matted hairs; leaves that are ridged or with tiny warts (called papillae) or scales on the underside of a thallose bryophyte may help water motion along the found by capillary action. It is instructive to add a tiny drop of h2o to a mat of dry bryophytes and watch the water move through the mat. Ideally, watch the process nether a low ability microscope.

In a number of bryophytes water is conducted internally, equally well as being absorbed in varying degrees through the plant surface. There are likewise varying degrees of development of the internal conducting organization. In some the internal conducting system is fairly rudimentary. On the other hand, mosses in the families Polytrichaceae and Dawsoniaceae have robust stems with well-adult internal conducting systems. However, fifty-fifty in these cases the internal conducting systems are not developed to the extent they are in the flowering plants.

You tin find out more in Volume i, Chapter 7, of Janice Glime's Bryophyte Ecology website.

Reproduction & dispersal

Bryophytes may reproduce both sexually and asexually. In flowering plants the flowers are essential in the sexual reproductive cycle, with the pollen (the male person gametes) from one bloom typically being carried to another by wind, insects or animals. Once the pollen has been deposited information technology volition fertilize the eggs in the receiving plant. Bryophytes have neither pollen nor flowers and rely on water to carry the male sperm to the female eggs. The spore capsules are produced after a male gamete (the sperm) has fertilized a female person gamete (the egg). Hence the spores are part of the sexual reproductive cycle. In the bulk of the bryophytes spore dispersal is by wind.

Winged spores of Asterella drummondii

The gametes are produced on what's called the gametophyte and the spore capsule (with its supporting stalk, if any) is called the sporophyte and this grows from the gametophyte. In mosses and leafy liverworts the stems and leaves make up the gametophyte. In hornworts and thallose liverworts the gametophyte is the flattish sail. In bryophytes the gametophyte is persistent, with the sporophytes sometimes present for only a short time. The termination "-phyte" means "plant", and so the gametophyte is the "gamete plant" and the sporophyte is the "spore plant". A germinating spore will eventually produce a new gametophytic institute and you can notice more in the LIFE CYCLE Department.

Bryophytes can reproduce asexually in several ways. Simple fragmentation is 1 method. If, say, a fragment of a bryophyte gametophyte lands in a suitable habitat it can grow into a new plant. Many bryophytes produce what are called gemmae. Each gemma is a small aggregation of cells, capable of growing into a new institute. The gemmae may be produced in specialised structures, equally tiny outgrowths from some function of the gametophyte or simply loose on the gametophyte. For example, here'south a picture of a gemma cup on the gametophyte of a species of Marchantia, a thallose liverwort. Inside the small loving cup y'all can see some small dark-green balls. Each of those is a gemma and may get splashed out by a raindrop or washed out by flowing water. In the moss Gemmabryum dichotomum the gemmae are and so abundant amongst the leaves that they show upwards in this picture equally simply a mass of brighter green.

You can find out much more in the REPRODUCTION & DISPERSAL Department.

How practise bryophytes differ from other plants ?

From what has been said above there's one clear deviation betwixt the bryophytes and the flowering plants. Bryophytes produce spores, rather than seeds, and take no flowers. But what about the ferns? They likewise have no flowers and produce spores. On the other hand ferns have well-adult, internal conducting systems that bear nutrients through the plant. The flowering plants likewise have such well-developed conducting systems, whereas bryophytes have, at all-time, relatively poorly-developed internal conducting systems. So, roughly speaking, ferns are intermediate between bryophytes and flowering plants, since they show some features of each.

All plants have gametophytes and sporophytes, but in that location is a considerable difference between the major plant groups equally to which is the dominant stage. In the bryophytes the gametophyte is dominant. Gametophytes are persistent and, from fourth dimension to fourth dimension, gives ascension to sporophytes. Spores produced past the sporophyte germinate to produce more gametophytes, which may and then give rising to more than sprophytes so on. We speak of an alternation of generations, between the gametophyte and sporophyte phases. In the flowering plants the sporophyte is the ascendant phase with the gametophyte reduced to just a few cells. Roughly speaking, ferns are in between.

Y'all can find out more in the LIFE CYCLE SECTION. In that department you lot'll find a clarification of the bryophyte life bicycle likewise as a comparison between life cycles of the bryophytes and the other plant groups and the differing roles of gametophyte and sporophyte.

How many bryophytes are there - and what's known about them ?

There are estimated to be between almost 12,500 and 15,000 bryophyte species known in the world, with about 2,000 from Australia. Here are the estimated numbers of species in each of the 3 BRYOPHYTE GROUPS:

	mosses	liverworts	hornworts
World	8,000 - x,000	iv,500 - 5,000	100 - 150
Australia	1,100	900	thirty

Many parts of the world are without resident bryologists, so that cognition of the bryophyte diversity in those areas has been gained in a haphazard style, typically from visits by bryologists resident elsewhere. This means that some areas of the world accept been well-studied, from a bryological perspective, while others are largely unexplored. For example, knowledge of African bryophytes is generally fairly poor and in Australia the greatest number of species are recorded from eastern Australia. In the Australian example, that may well reverberate the concentration of bryologists, rather than species, in eastern Australia. In the years since European settlement, there accept been few bryologists resident in Commonwealth of australia and you can read more in the department dealing with the HISTORY OF AUSTRALIAN BRYOLOGY.

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Spore capsules of Tayloria gunnii

Despite the patchy cognition near the globe'southward bryophytes, diverse distribution patterns practise testify themselves. There are virtually cosmopolitan species (eastward.g. the thallose liverwort Lunularia cruciata ), Gondwanan species, Australasian species, polar species...and numerous other patterns down to those with a very restricted distribution. An instance of the last is Tayloria gunnii, a species with very striking spore capsules, which is found but in Tasmania. There'south more than on the subject of bryophyte distributions in the section on BRYOGEOGRAPHY. Some of the widespread species are undoubtedly naturally widespread while others take been inadvertently dispersed by humans.

Ecology

Bryophyte ecology is a large subject field. For the moment we'll deal with diverse aspects by means of very cursory summaries. All of these aspects (plus some others) are covered in more particular in the section on BRYOPHYTE ECOLOGY.

Extensive carpets of bryophytes on soil help in moisture conservation and flood control. During sudden downpours numerous species can quickly absorb (and retain) many times their dry out weight in water. The absorbed h2o is then gradually released over a longer catamenia, reducing the erosive furnishings of heavy rain and allowing other plants to benefit for a longer flow from the rain. Bryophytes are besides practiced at trapping nutrients from the air. This is the case for bryophytes that carpeting the ground, simply even more so for the curtains of bryophytes that are common in moist areas, such equally rainforests . As mentioned above, most bryophytes blot nutrients through their surfaces. An extensive bryophyte curtain has a large surface expanse. This means at that place's a big area through which the curtain tin blot the nutrients carried by h2o in mist or rain. These nutrients somewhen become bachelor to other organisms, for example if something eats a bryophyte or after a bryophyte dies and decays.

Some species are very effective sand and soil binders and can help in dune stabilization and erosion command. In arid areas bryophytes, in association with lichens, can create extensive crusts on the soil and such crusts help maintain the underlying soil structure.

Bryophyte colonies provide niches for numerous invertebrates, frequently the very tiny invertebrates, which are and then eaten by larger invertebrates which, in turn, are eaten past other creatures. Such bryophyte colonies are thus indirectly important in various nutrient chains.

Bryophytes are often the kickoff plants to colonize arid surfaces (due east.grand. road cuttings, rock outcrops and volcanic ash) and fix these areas for after plants past trapping moisture and windblown organic droppings and then contributing to the organic deposits when they themselves die and decay. This photo shows an all-encompassing moss carpeting growing over a large stone outcrop in a Western Australian sclerophyll forest. Here is a closer view of another moss mat (on stone) in which numerous vascular shrubs and herbs accept established themselves. In this photograph you can see numerous blood-red Drosera plants (besides as some Siphula, a whitish lichen) in a rug of moss. Moss carpets tin can too aid the seeds of flowering plants in germination by providing a moist seed bed. On the other mitt, some bryophytes may inhibit the germination of the seeds of sure plant species. In short, there are many types of interactions between bryophytes and other plants.

Some aquatic bryophytes participate in rock germination by absorbing minerals dissolved in the water. When dead, the plants sink to the bottom and so deposit the absorbed minerals.

Never say die

White winged choughs (Corcorax melanorhamphos) are mutual birds in the grounds of the Australian National Botanic Gardens. When feeding they flick leaf litter or mulch aside with their solid beaks and use those beaks to dig into the soil in search of invertebrates. Choughs work in groups of 10 or and then and can turn over a considerable amount of leaf litter - or mosses. One surface area that sees chough visits is a garden bed with a long-established colony of the moss Campylopus introflexus. In this species numerous stems grow shut together to form a dense moss carpet. In such a dense carpeting active, photosynthesizing leaves will be confined to the upper parts of each stem since the lower stems would be too heavily shaded. Moss carpets are often homes to invertebrates and a moss carpet presents no obstacle to a chough. The bird will only pull out or flick away chunks of moss in its search for food. What of a fragment that lands upside down? In an overturned fragment the leaves are cut off from the sun, unable to photosynthesize and then the plant would die - right? No. New stems and leaves start growing from the base (now top) of the fragment and from the stems. This photo shows such an upturned fragment, with many new shoots growing from various parts of the fragment. Various mosses show such behaviour, some to such an extent that over time, once a clump has been dislodged a number of times in different directions and shoots have grown from all sides, the result is a somewhat-ball like clump with shoots from all directions - a moss brawl.

Looking for bryophytes - and microhabitats

It'due south already been said that you can find bryophytes nearly anywhere in the non-marine globe, so you lot're bound to come across them. Sometimes it's piece of cake to make sense of what you see, merely at other times it'south more of a challenge. There's no difficulty in seeing this drape of the moss Papillaria flavolimbata. Moreover all of this drape is the one species. At the other extreme there are many small-scale bryophytes and very frequently y'all'll find different bryophytes growing together. This photo shows two mosses, an unidentified green species and the silvery Erpodium hodgkinsoniae growing intermixed. Given the colour contrast it's easy to see that there are ii species here. This photo shows some thallose bryophytes. The darker green surface area is a hornwort in the genus Megaceros and the thallose liverwort genus Riccardia makes up the brighter dark-green area. In that brighter dark-green area there are in fact two species - Riccardia colensoi and Riccardia bipinnatifida. Telling the hornwort from the liverworts is fairly easy, since there's plenty of a difference in the shades of green, merely to distinguish one Riccardia from the other needs a much closer expect, down on your hands and knees. Finally, this photo shows part of a stone wall at the Australian National Botanic Gardens, with mosses growing in the joints between the separate stone slabs. In that location are at least iii different moss species (in three dissimilar genera) shown in this view. In this instance you lot definitely need to await very closely, with a manus lens, in guild to distinguish the three species. This photo likewise illustrates the significance of MICROHABITATS. From a bryophyte perspective, the microhabitat in the joints is different to that on the face of a rock slab. Microhabitats are very important to bryophytes and then, when looking for bryophytes y'all need to be aware that as you walk a few metres y'all may well be passing through a diverseness of microhabitats, each providing different growing conditions and each host to different bryophytes. Here is another instance of a bryophyte, the moss Gemmabryum dichotomum, exploiting a microhabitat that is located in this macro-habitat.

Too as finding bryophytes growing with other bryophytes, y'all'll as well often find them growing with OTHER CRYPTOGAMS. In this photo you lot can see a very dark dark-green band of moss extending diagonally from near the upper left corner towards the lower right. As obvious is a great mass of a low-growing greyish lichen in the genus Siphula. A picayune to the correct the cauliflower-like growths are colonies of a lichen in the genus Cladia. To the left of that band of moss the "bare" rock is home to lichens in the genus Xanthoparmelia.

Are they simple plants ?

Bryophytes are often considered to be amongst the simplest and most primitive of plants in that, dissimilar the ferns and flowering plants, they haven't a well-developed system for conveying nutrient solutions along their stems. Such a conveying system is called a vascular arrangement and hence bryophytes belong to the grouping of non-vascular plants. Bryophytes lack true roots though many species have root-like anchoring rhizoids. But how simple or primitive are they? Consider the following evidence:

bryophytes produce many phenolic and related compounds that deter herbivores;
they were on the earth before the flowering plants and are still here;
they inhabit a variety of habitats - even exposed arctic rocks, nighttime forest logs, acid bogs, tree trunks, boulders washed by fast-flowing streams, weathered bones and glass surfaces;
how many vascular plants could survive long periods of desiccation without any underground organ or specialized resting structure? Moreover, bryophytes and their chlorophyll tin survive intense lite while dehydrated, a combination that would chop-chop fade a vascular leaf;
how many other plants can grow during periods of sub-zero temperatures?

Afterward taking all this into business relationship one bryologist commented that along with the insect that survives whatsoever earthly holocaust there will be a forest of moss to give information technology shade and shelter.