3. Kingdom Plantae - part 01 - Division : Thallophyta

 

3. Kingdom Plantae - part 01 - Division : Thallophyta

Kingdom plantae :
  •  Kingdom Plantae is further classified on the basis of characteristics like -  
  1. absence or presence of seeds
  2. vascular tissues
  3. differentiation of plant body, etc.
Phanerogams
  • Phanerogams  are commonly called seed producing plants. 
  • They produce special reproductive structures that are visible (Phaneros – visible)
Cryptogams :
  • Cryptogams are spore producing plants and do not produce seeds and flowers.
  • They reproduce sexually by gametes but sex organs are concealed (kryptos : hidden, gamos : marriage).
Classification of Kingdom Plantae :

Salient features of major plant groups under Cryptogams :

A. Division : Thallophyta -
  •  Members are mostly aquatic, few grow on other plants as epiphytes. 
  • Some grow symbiotically and epizoic i.e. growing or living non-parasitically on the exterior of living organisms. 
  • Aquatic algae grow in marine or fresh water. 
  • Most of them are free living while some are symbiotic.
  • Plant body is thalloid i.e. undifferentiated into root, stem and leaves. 
  • They may be small, unicellular, microscopic like Chlorella (nonmotile),Chlamydomonas (motile). 
  • They can be multicellular, unbranched, filamentous like Spirogyra or branched, filamentous like Chara. 
  • Sargassum, a huge macroscopic sea weed which measures more than 60 meters in length is also an alga.
  • The algal cell wall contains either polysacchrides like cellulose / glucose or a verity of proteins or both. 
  • Reserve food is in the form of starch and its other forms. 
  • Reprocuction takes place by vegetative asexual and sexual way. 
  • The life cycle shows phenomenon of alternation of generation, dominant haploid and reduced diploid phases.
classification of Algae [as per its pigments like chlorophyll, xanthophyllsand phycobilin.]
  1. Chlorophyceae 
  2. Phaeophyceae 
  3. Rhodophyceae 

1. Chlorophyceae (green algae) :

  • These are mostly fresh water (few brackish water and marine).
  • Plant body is unicellular, colonial,
    filamentous. 
  • Cell wall contains cellulose. 
  • Chloroplasts are of various shapes like discoid, plate-like, reticulate, cup-shaped, ribbon-shaped or spiral with chlorophyll a and b. 
  • The stored food is in the form of starch.
  • Pyrenoids are located on Chloroplast.
  • Members are rich in protein, so used as food; used even by space travellers.
  • e.g. Chlorella. Chlamydomonas, Spirogyra, Chara, Volvox, Ulothrix etc.








2. Phaeophyceae (Brown algae) :

  • Plant body : Mostly marine, rarely fresh water. 
  • Simple branched / filamentous (e.g. Ectocarpus) / profusely branched (Petalonia).
  • Cell wall has cellulose, fucans and algin. 
  • Photosynthetic pigments like chlorophyll-a, -c and fucoxanthin are present.
  • Mannitol, laminarin and starch are stored food materials. 
  • Body is usually differentiated into holdfast, stalk called stipe and leaf-like photosynthetic organ called frond. 
  • Many species of marine algae are used as food. 
  • e.g. Porphyra, Laminaria, Sargassum. 
  • Some species are used for production of hydrocolloids. e.g. Ectocarpus, Fucus, etc.






3. Rhodophyceae (Red algae) :

  • Plant body These are found in marine as well as fresh water on the surface, deep sea and brakish water.
     
  • Plant body is thalloid. 
  • Cells contain chlorophyll a, d and phycoerythrin.
  • Cell wall is made up of cellulose and pectin glued with other carbohydrates. 
  • Stored food is in the form of Floridean starch. 
  • Commercially important agar-agar which is used as solidifying agent in tissue culture medium is obtained from red algae. 
  • e.g. Chondrus, Batrachospermum Porphyra, Gelidium , Gracillaria, Polysiphonia, etc.

Do u know ?

  • Brown algae- kelps may grow up to 100 meters in height. 

Comments

  1. UnknownMay 11, 2021 at 1:58 AM

    Thank you sir for writting such a brief notes it helps us a lot.

    ReplyDelete

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