Rhodophyta

red algae

1. By Subhananthini jeyamurugan Roll no 18py17 I M.Sc., Microbiology Rhodophyta (red algae)

2. Classification of R hodophyta

3. Florideophyceae Nemaliales Corallinales Lithophyllum Corallina Gelidiales Gelidium Gigartinales Chondrus crispus Used as a source of carageenan Rhodymeniales Ceramiales Polysiphonia polysiphonia

4. Division : Rhodophycophyta class : Rhodophyceae sub-class : Florideae order : Gelidiales Family : Gelidiaceae Genus : Gelidium Species : cartilagineum Systemic Position

5. Accessory pigments! Phycobilins mask the Chlorophyll a – thus they look red. Due to these accessory pigments, red algae can photosynthesize in deep water (at different light wave lengths). Why are Red algae red?

6. Introduction Floridean starch is a type of a storage glucan found in red algae (also known as rhodophytes), in which it is usually the primary sink for fixed carbon from photosynthesis. Floridean starch is stored as grains outside the chloroplast

7. Thallus – cylindrical or flattened It is stiff and cartilaginous and often pinnately branched. I n many species branch lets bend away from the main axis The thallus is based primarily upon the uniaxial type of construction . I t possess the single apical cell at the apex of each branch. The apical cell forms a single axial filament of the adult portion . T he axial filament, one or two posterior to the apical cell cut off four primary pericentral cells . And then each of these cells form a short branched lateral filament . T he tips of these lateral filaments adhere to each other and form pesudoparenchymatous tissue that makes the surface of the thallus. Structure of Thallus

8. Thallus organization

9. Continue…

10. Red algae have double cell walls . The outer layers contain the polysaccharides agarose and agaropectin that can be extracted from the cell walls by boiling as agar . The internal walls are mostly contain cellulose. M orphology

11. R eproduction Vegetative Reproduction is by fragmentation Asexually by non-motile spores Sexually by non-motile gametes e.g., P olysiphonia, Porphyra, Gracilaria, Gelidium.

12. Life cycle sexual Asexual

13. In majority of class it takes place by fragmentation. In sexual reproduction of the gametophytes takes place by neutral spores , mono spores and polyspores. neutral spores develop in ordinary cells of thallus. monospores develop in sporangia. polyspores are formed in larger number in the sporangium. Vegetative reproduction Asexual reproduction

14. Continue… The asexual reproduction of the sporophytes takes place by tetra spores formed in tetrads in the tetra sporangia ( Tetra sporangia produce tetra spores via meiosis) e.g ., Polysiponia . Paraspore borne inside parasporangia in greater numbers. During the development of tetraspores reduction division takes place. In the development of paraspores there is no reduction division.

15. The sexual reproduction is always in Oogamous. The oogamy is a special type. M ale structure is called the Spematangia developing non- motile spermatia ( male gametes) in them. Female structure is called the procarp. It has a carpogonium bearing a receptive structure is called trichogyne. The egg develops in the basal swollen part of carpogonium. Sexual reproduction

16. life cycle may be haplotonic, haplobiontic or diplobiontic. Florideophyceae Life cycle typically diplohaplontic, some are haplontic Many have a complex modification of a diplohaplontic life cycle Triphasic alternation of generations Gametophyte (may or may not be dioecous) Carposporphyte Tetrasporophyte The low efficiency of fertilization Life cycle

17. Life cycle

18. Economic importance of red algae B enefits

19. Continue… Medicines: Corallina is capable of curing worm infections. Polysiphonia has anti­bacterial properties. Agar is laxative. Carrageenan can coagulate blood

20. A number of red algae are edible, e.g ., Porphyra (Laver), Rhodymenia (Dulse), Chondrus (Irish Moss). Rhodymenia (also called sheep’s weed) is also used as fodder . Porphyra is cultivated in Japan for commercial exploitation. Food

21. Harmful Some red tides are associated with the production of natural toxins, depletion of dissolves oxygen or other harmful algal blooms. T he most conspicuous effects of these kind of red tides are the associates wildlife moralities of marine and coastal species of fish, birds, marine mammals and other organisms.

22. Ask your doubts…