Salient features of Phaeophyta

Division - Phaeophyta:-

Salient Features:-

> Cell construction:- Cellulose fibers bound with Alginic acid ,Fucuni acid, Fucoidan form cell walls.

> Food reserves:- laminarin, mannitol.

> Photosynthetic pigments:- chlorophyll a and c, beta carotene, Dinoxanthin ,violaxanthin, and Fucoxanthin. These pigments give brown algae color and Fucoxanthin pigment are dominant.

> Morphology:- Members of this division typically have three parts. They are:

i. Holdfast:- which attachment the alga to the substrate

ii. Stipe:- which is stem-like

iii. Laminae (blades):- which are leaf-like

> Phaeophyta (Sea weeds) belonging to order Laminarales are called kelps can reach to about 70 meters in length. Kelps are the only algae with a significant internal tissue differentiation. Kelp grows in "underwater forests" in shallow oceans, Though true conductive tissues , xylem and phloem are absent.

> Brown algal tissue differentiation:- Epidermis, Cortex and Medulla.

> They can adapt to a wide marine environment; tidal, intertidal and deep zones.

> Some members of phaeophyta have Containing bladders or airbags, meant for floating photosynthetic parts on or near the water surface for harvesting light.

> They often cause nuisance to aquarium environment by developing brown patches on any exposed surfaces such as rocks or gravel.

> Reproduction:- This takes place by both sexual and asexual means. Higher phaeophyta have life cycle consisting of both haploid, diploid stages and alternation of generation. The thallus representing haploid stage and diploid stage may be similar (isomorphic) or different (hreteromorphic).

Classification:-

Class:- Paeophyceae

3 Sub-classes:-

a. Isogeneratae:- Isomorphic alternation of generation.

Order:- Ectocarpales

Eg.- Ectocarpus

b. Hetrogeneratae:- Heteromorphic alternation of generation.

Order:- Laminarales “Kelp or Rock weed"

Eg.- Laminaria

c. Cyclosporeae:- 

Order:- Fucales

Eg.- Fucus, Sargassum