Water is essential for reproductive activities. For instance, most mosses have water-conducting cells called hydroids in the centers of their stems, and some even have food conducting cells called leptoids. These cells are not nearly as efficient as xylem and phloem and generally, bryophytes are not very tall plants.
The lack of vascular tissue leaves the plant body very soft and pliable. The sporophyte generally looks like a slender stalk with a cap on top. While the lifecycles of all bryophytes are similar and even their chromosome number and habituation have similarities; they are divided into three distinct groups based on the few differences in structure and reproduction. Wort means plant or herb, and in ancient times herbalists thought that some of them —specifically the ones that look like liver lobes— were useful in treating liver ailments.
Although, the belief was discounted the name stuck. They lack true stomata, which are present in hornworts and mosses. Mosses are more complex than liverworts. They have one-celled rhizoids on their lower surfaces. The rhizoids look like tiny roots and anchor the plants to surfaces and soil particles. The thalli are the gametophyte generation and develop almost directly from spores. They have smoother upper surfaces and the cell wall corners are thickened. Marchantia is the best-known species of thalloid liverwort.
It can usually be found on damp soil after a fire. Marchantia can reproduce asexually and sexually. Asexual reproduction is accomplished through gemmae, which are tiny lens-shaped pieces of tissue that detach from the thallus. Gemmae cups are produced along the upper surface of the gametophyte. Lunularic acid inhibits the Gemmae from growing, as soon as it is out of the cup, though, the inhibition is removed and each may develop into a new thallus.
Sexual reproduction in the Marchantia involves the interaction between spores on separate male and female gametophytes. The gametangia are formed on gametophores, or umbrella-like structure on long stalks.
The stalks are positioned between the grooves of the thallus. The male gametophore is shaped like a disc with a scalloped edge, while the female gametophore looks like the hub and spokes of a wheel.
The female gametangia are flask-like and each one contains a single egg. They are produced in rows and hang with their neck downward from the archegoniophore. Rain will splash and release the flagellated sperm cells. The stalks of the archegoniophores may not be finished growing at the time of fertilization.
The zygote, fertilized egg, will develop into a multicellular embryo a. The foot is connected to the sporophyte also referred to as the capsule, out of which develops the various type of tissues by a short, thick stalk called the seta. Inside the capsule, spore mother cells undergo meiosis which results in haploid spores. Some capsule cells do not undergo meiosis, but remain diploid and develop into elaters, which are long and pointy and responsive to changes in humidity. What are bryophytes?
As they are not flowering plants, bryophytes reproduce by spores instead of seeds. Juan Carlos Villarreal currently studies bryophytes in the arctic regions of Canada. Credit: Sean Mattson. Prints of Octoblepharum peristomiruptum, the new species of moss discovered by Noris Salazar Allen, which appear in her publication in the scientific magazine PhytoKeys in The benevolence of bryophytes However small, these plants have a very big and important role in the ecosystem: absorption.
Phyllogonium species, a hanging moss, at Altos de Campana National Park. Leiosporoceros dussii Steph. Credit: Maritza Moya. Share On. Explore more science. Related stories. Ocean trotters. Ancestors of whale sharks in Panama may come from distant waters. Counting bees. Orchid bees show remarkable resistance to major climate events. Ecosystem Ecology Long-term monitoring. Andrew Sellers. Marine Protected Areas. Bird disappearances. Biodiversity loss despite a century of protection.
Biodiversity Forest Ecology Ecosystem Ecology. Understanding wildlife vulnerability to road networks. Ecosystem Ecology Biodiversity Animal Behavior. Intact wilderness. Exploring the cloudiest forest in Central America. A well known example is Spanish Moss - which is a flowering plant. Gigaspermum repens , a moss. Getting back to mosses, on the right is a photograph of Gigaspermum repens , a moss with white leaves.
Mosses don't have flowers. Not to be outdone in colour variety here are two thallose liverworts, the green and white Riccia crystallina and the red-margined Riccia cavernosa. Virtually all bryophytes contain chlorophyll and so make their own food from water and carbon dioxide, via photosynthesis. There is one 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 grow to strands well over a metre long. A common misconception is that to find bryophytes you need to be in a damp, shaded streamside — preferably not in summer.
In fact bryophytes can be found in great variety throughout the year in areas ranging from arid to rainforest, and in habitat from sea-level to alpine. They occur most abundantly in relatively unpolluted areas. Some species have 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, bones, old discarded shoes or gloves — to name a few possibilities.
They have root-like anchoring structures, called rhizoids , but these unlike the roots of most plants do not actively extract minerals and water from the substrate. A great many bryophytes are able to survive dormant during periods of extreme dryness or extreme cold and the species living in harsh environments have various survival mechanisms. Many moss species in such areas grow cushion-like , each cushion being a dense colony of individual plants. In this way most of the colony is protected from the direct effect of the harsh conditions.
Many arid area bryophytes curl up in various ways to reduce their exposed surface areas. In various species the chlorophyll undergoes a change in structure in order to survive the dry periods undamaged. Dormant bryophytes can become active with just a little water. It need not even be rain - fog or dew will be enough in many cases. This is why you can find bryophytes in deserts where rainfall may be very rare. In such areas the nights can still get cold, resulting in early morning dew formation - enough to bring the bryophytes out of dormancy.
They can 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 as this the absorbed water 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 move along the plant by capillary action.
It is instructive to add a tiny drop of water to a mat of dry bryophytes and watch the water move through the mat. Ideally, watch the process under a low power microscope. In a number of bryophytes water is conducted internally, as well as being absorbed in varying degrees through the plant surface. There are also varying degrees of development of the internal conducting system.
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-developed internal conducting systems. However, even in these cases the internal conducting systems are not developed to the extent they are in the flowering plants. Bryophytes may reproduce both sexually and asexually. In flowering plants the flowers are essential in the sexual reproductive cycle, with the pollen the male gametes from one flower typically being carried to another by wind, insects or animals.
Once the pollen has been deposited it will 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 gamete the egg. Hence the spores are part of the sexual reproductive cycle. In the majority of the bryophytes spore dispersal is by wind. In mosses and leafy liverworts the stems and leaves make up the gametophyte.
In hornworts and thallose liverworts the gametophyte is the flattish sheet. In bryophytes the gametophyte is persistent, with the sporophytes sometimes present for only a short time. Bryophytes can reproduce asexually in several ways.
Simple fragmentation is one 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 plant. The gemmae may be produced in specialised structures, as tiny outgrowths from some part of the gametophyte or simply loose on the gametophyte. Within the small cup you can see some small 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 so abundant amongst the leaves that they show up in this picture as simply a mass of brighter green. From what has been said above there's one clear difference between the bryophytes and the flowering plants. Bryophytes produce spores, rather than seeds, and have no flowers. But what about the ferns?
They also have no flowers and produce spores. On the other hand ferns have well-developed, internal conducting systems that carry nutrients through the plant. The flowering plants also have such well-developed conducting systems, whereas bryophytes have, at best, relatively poorly-developed internal conducting systems.
So, roughly speaking, ferns are intermediate between bryophytes and flowering plants, since they show some features of each.
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