Economical importance of bryophytes

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ECOLOGICAL IMPORTANCE OF BRYOPHYTES Mosses and Bryophytes are the first organiasms to colonise rocks. They colonise rock by acidic secretion. This acidic secretion is due to the death of mosses. When the rock is decomposed it helps in soil formation. Therefore New soils are formed. The soil act as binders.  It prevent soil erosion. The water retention capacity of the soil is high ie, water holding capacity of the soil is high.  This reduces surface water run-off which prevent soil erosion. Bryophyte helps in the recycling of nutrients. ECONOMICAL IMPORTANCE OF BRYOPHYTES. 1) SPHAGNUM Sphagnum has high absorptive power with antiseptic property. This can be used to replace cotton in bandages. 2) MERCHANTIA   Mercahntia cures pulmonary tuberculosisand affliction (pain) in liver. Antibiotic substances are also extracted from bryophytes. it also acts as antiseptic, and as preservative POLYTRICHUM Polytrichum dissolove stone in kidney and in gall bladder. 3) IN RESEARCH It is used in the fie
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Class Chlorophyceae general characters and classification, notes

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Chlorophyceae( Green algae) 
   The group of green algae represented by 425 genera and 6500 spe species ( Bold i 1967) . Fritsch considered to include the group of green algae in the class chlorophyceae. While Smith, Bold etc raised to the rank of division chlorophyta. They are the biggest class of algae. 

  In the classification of these algae numerous features are taken into consideration, such as nutritional requirements, morphological and structural features, Serological reactions, ultrastructure and composition of cell wall etc. 
      
   They are green due to the predominantly pigments chl a, and b found in abundance, also other pigments are present ie. alpha, beta carotene an xanthophyll but phycobillins are absent. They are found in almost every where,.most are fresh water (about 90%) also some are marine in habits. The fresh water maybe pools, lakes, and ponds etc. Some are found in both Mari as well as fresh water ie. Volvocales, Cladophorales etc. Some  species are sub aeriel  and usually found on damp soil in the form of sheet, some species are epiphytic, epizoic, and endozoic. The parasitic  algae lack green colour ie Cephaleuros causes red- rust in tea. Some species occur in the unusual habitats.ie.some are thermophilic species, found in hot springs ( chlorella) ,chlymadomonas etc are found in snow covered mountains, some species are inhabits in saline water.. Some green algae are in association with certain fungus constitude lichen. 

Distinguished features of chlorophyceae. 

1. The cell structure is eukaryotic. 
2.mainly the cell wall is two layered the inner is Cellulosic and outer is pectate materials,, cellulose is the main structural polysaccharides except for siphonaceous which have mannan and xylan. In Chara the cell wall is impregnated with calcium carbonate. 
3. The protoplast bounded by semipermeable plasma membrane , cytoplasm possess small vacule or  large contractile vacuole. 
54. Like other eukaryotes they have other cell organelles ie. Mitochondria, membrane bound plastids etc. 
5. The Main pigments are chl a and b, but alpha, beta carotene and xanthophylls are also present. Phycobillins are absent. 
6. The shape of chloroplast show much variations ie cup shape ( Chlamydomonas) , spiral( Spirogyra) etc. 
7. The chloroplast normally contains pyrenoids surrounded by a sheath of starch. 
8.they exhibit a wide range in their thallus structure and morphology. 
i. Unicellular  motile( chlymadomonas) , non motile ( Chlorella) 
ii. Coenobium( volvox) 
iii. Palmelloid( Tetraspora) 
iv. Dendroid( ecballocystis) 
v. Fillamentous   branched( Cladophilora) , unbranched ( spirogyra) 
vi. Heterotrichous( Coleochate) 
vii. Siphonaceous ( codium) 
viii. Parenchymatous,( ulva) 

9.They have a well organized nucleus, usually there's a single nucleus in each cell, but the members of siphonales and cladophorales are coenocytic. In general there's a single nucleolus per nucleus, but in Conjugales  there are several nucleoli in a nucleus. 
10.most of the flagellate cell have a photosensitive red eye spot or stigma in the anterior position, nearer the flagellar base. 
11.reserve food is mainly starch composed of amylum and amylopectin. Some have small amount of oils. 
12.  The motile cells have two, rarely four, of equal , smooth flagella. However, in Oedogoniales the motile cells a crown flagella. In a few instances( eg., Haematoccous) , there are two pleuronematic flagella. 
13.they repeoduce by vegetative( cell division,fragmentation) , asexual( Akinetes, Zoospore and Aplanospore) and sexual( occurs in all membres except some Chlorococcales. It maybe isogamous,anisogamous and Oogamous) 
methods.
14. The zygote or or Oospore secrete a thick wall and undergoes a resting period. It germinates in favourable cold and forms a new thallus. 

Classification of Chlorophyceae
     Fritsch (1935) , on the basis of morphology and reproductive characters recognised the following nine orders in chlorophyceae. 

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