Class Musci

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Class Musci

Mosses



STRUCTURES

• Mosses are anchored in the soil withthin rhizoids .

• Moss leaves usually consist of a

single cell layer and are traversedby a midrib that is always morethan one cell in thickness.

•

The margins of the leaves are oftentoothed, the teeth pointed orrounded.



The sporophytes of mosses, like those of theliverworts, consist of a foot, seta and capsuleand remain permanently attached to thegametophytes. They are borne at the tips oferect gametophytes (a) or the tips of theshort lateral branches of prostrategametophytes (b).



During the early stages ofdevelopment, the sporophyte

is completely surrounded by atough protective coveringcalled the calyptra.

The peristome teeth are

perhaps the mostcharacteristic feature of themosses; usually composed ofcell wall remnants, they

respond to changes in thehumidity of the atmosphere.



• Under suitable conditions,a spore will germinate and

give rise to a microscopicchlorophyllous branchedfilament from which,eventually, the leafygametophytes will arise.The gametophytegeneration of the mosses

is, thus, dimorphic.



• The moss usually illustrated in

introductory botany textbooks isPolytrichum.

• The gametophytes and

sporophytes, although devoid ofxylem and phloem, contain water-and food-conducting cellsanalogous to those of vascularplants.



• The gametophytes andsporophytes, althoughdevoid of xylem and

phloem, contain water-and food-conducting cellsanalogous to those ofvascular plants.

• The mouth of the capsuleis covered by amembrane that is

overarched by massivemulticellular peristometeeth the tips of whichare joined to the

membrane.



REPRODUCTION• The life cycle begins with two mature

gametophytes.

• Females develop Archegonia and malesdevelop Antheridia which produce gametes bymitosis.

• The sperm is flagellated and needs water toget to the egg.

• The sporophyte is very small and dependenton the gametophyte.



Note:

• With the exeception of when thesporangium produces spores (Meiois),cell divisions in the entire life cycle of

the mosses are Mitotic.• The cells are Haploid (1N) throughout

the Gametophyte generation. (Fromspore to mature Gametophyte)

• The cells are Diploid (2N) throughoutthe Sporophyte generation. (Zygote toSporophyte)

HABITATS AND



HABITATS ANDDISTRIBUTION

HABITAT

Mosses have a damp environment in w/c togrow, & a surrounding of liquid water toreproduce.

Mosses are autotrophic they require enoughsunlight to conduct photosynthesis.

Mosses grow chiefly in areas of dampness andshade, such as wooded areas and at the edgesof stream; but they can grow anywhere in cooldamp cloudy climates, and somes species areadapted to sunny, seasonally dry areas

likealpinerocks os stabilized sand dunes.



Moss species can be classed as growing on:rocks, exposed mineral soil, disturbed soil,calcareous soil, cliff seeps and etc.

Mosses often grow on trees as epiphytes, theyare never parasitic parasitic on the tree.

Mosses are also found in cracks between pavingstones in damp city streets, and on roofs. Some

species adapted to disturbed, sunny areas arewell adapted to urban conditions and arecommonly found in cities. Examples would be

Rhytidiadelphus squarrosus, a garden weed

in Vancouver and Seattle areas; Bryumargenteum, the cosmopolitan sidewalk moss,and Ceratodon purpureus, red roof moss,

another cosmopolitan species.



DISTRIBUTION

• Bryophytes are distributed throughoutthe world, from polar and alpine regionsto the tropics.

•

Water must, at some point, be present in thehabitat in order for the sperm to swim to theegg. Bryophytes do not live in extremely aridsites or in seawater, although some are found

in perennially damp environments within aridregions and a few are found on seashores

above the intertidal zone.



• The greatest diversity is at tropical andsubtropical latitudes. Bryophytes

(especially the mossdominate the of peatland inextensive areas of the cooler parts of theNorthern Hemisphere.

• The distribution of some bryophytes,however, is extremely restricted, yet theypossess the same apparent dispersibility

and ecological plasticity as do widespreadbryophytes. Others show broadinterrupted patterns that are represented

also in vascular plants.

http://www.britannica.com/EBchecked/topic/624629/vegetation

http://www.britannica.com/EBchecked/topic/559546/Sphagnum



IMPORTANCE TO MANAND ECOLOGY

• Mosses plays a vital role in thebiosphere even they are small in size.

•

Bryophytes cause the outer portion ofrock to slowly crumble as they growwith lichens on rock surfaces.

•

Some bryophyteslike sphagnum or peat moss hassome economic importance.



• Two major groups of mosses arerecognized, (The form asmall group comprising the

genera and .)

• Sphagnum often grows in dense mats inacidic boglands.

http://www.britannica.com/EBchecked/topic/23914/Andreaeobryum

http://www.britannica.com/EBchecked/topic/23908/Andreaea

http://www.britannica.com/EBchecked/topic/241704/granite-moss



ADVANTAGES OF MOSSES

• Easy planting process

• Garden and lawn beautification

• Herbal applications



DISADVANTAGES OF MOSSES

• Disease- Sporotrichosis is a fungal disease thathas been associated with sphagnum moss. Thedisease occurs because of a fungus known asSporothrix schenckii.

•

Water Absorption- Sphagnum moss absorbs andretains any water that comes within reach. Twoproblems occur when using the moss for growingplants. The first is that the soil stays too moist forthe plant because the sphagnum moss retains themoisture for long periods. The second problem isthat the moss could dry out the soil around theroot system, because it has absorbed the waterfrom that section of soil.

• Environmental Concerns

Class Musci

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