Life cycle pattern and perennation of algae

life cycle pattern of algae
perennation of algae

1. GURU GHASIDAS VISHWAVIDYALAYA RAKESH GADHEWAL AND SAIKAT JANA PERENNATION AND LIFE CYCLE PATTERN OF ALGAE PRSENTED BY – ( M.Sc sem - 1) 01/19

2. PERENNATION OF ALGAE Perennation is the ability of organisms to survive under unfavourable environment(drought or winter). It typically develops perennating organ, which stores enough nutrients to sustains the organism during the unfavourable season and develops into new plants next year. Perennation organs remains dormant during unfavourable conditions and form new plant by germination on favourable conditions. 02/19

3. AKINETES: Akinetes are resting spores formed to tide over adverse conditions such as dryness. Hence, they maintain perennation (live for more than one year). Any vegetative cell can develop into an akinete . During this process, it stores food materials forming a thick wall around. When favourable conditions return the cell germinates to produce a new filament Vaucheria Ulothrix SOME IMPORTANT PERENNATION STRUCTURES OF ALGAE 03/19

4. MUCILAGENOUS SHEATH : Mucilaginous sheath is the outermost layer covering the cell wall . The presence of a mucilaginous sheath is a characteristic feature of cyanobacteria . This is also known as the slime layer. Spirogyra Nostoc 04/19

5. PALMELLA STAGE : During unfavorable condition vegetative cells divide rapidly to form a colony of daughter cells. All these cells remain gelatinised and the entire structure becomes enlarged much more. This stage looks like anothesr green algae Palmella and this stage is called palmella stage or palmelloid stage. During favourable condition the unit bodies develop into individual zoospore and developes new thallus . Palmella stage of Chlamydomonas 05/19

6. HYPNOSPORES : These are formed during drought condition. Thick walled non motile cells . Remain dormant during unfavorable condition . During favorable condition they germinate and form new thallus . Ulothrix 06/19

7. HORMOSPORES : These are actually fragments of trichomes called hormogonia . Hormospores tide over unfavorable condition, and when favorable condition exists they germinate to produce new thallus . Nostoc 07/19

8. APLANOSPORES These are thick walled non motile spores which are formed during unfavorable condisions . They are formed from a part of a protoplast of a vegetative cell and developes thick wall. Aplanospores are liberated by the separation of parent wall. After a period of rest and on the approach of favorable condition they develop into new plants. Example- Chlamydomonas , Ulothrix , Oedogonium . 08/19

9. TUBERS : Multicellular spherical struture form due to division of rizoidal cells. Contain reserve food materials. These structures are well adapted for adverse conditions. Example : Chara , Cladophora etc. 09/19

10. ZOOSPORES : In chlorophyceae zygote formed as a result of sexual reproduction produce thick wall around and remain in dormant stage. These zygotes are known as resting spores. During favorable conditions they form new thallus . Example : Chlamydomonas   1 /19

11. LIFE CYCLE PATTERN OF ALGAE In the life cycle of an alga a number of distinct morphological and cytological stages can be observed. On the basis of these stages and there duration one can specify what type of life cycle an alga shows. There are mainly three types of life cycle reported in algae : Haplontic type Diplontic type Haplodiplontic type : A. Biphasic i . Isomorphic type ii. Heteromorphic type B. Triphasic i . Haplobiontic type ii. Diplobiontic type 11/19

12. HAPLONTIC TYPE This is the simplest and most premitive type of life cycle. The other patterns of life cycle have originated from this type. This type is found in all chlorophyceae except a few. Example – Chara , Oedogonium , Chara , Volvox 12/19

13. DIPLONTIC TYPE This pattern is reverse of haplontic type. In this case somatic phase is diploid while the haploid phase is restricted to gametes which are produced by meiotic division. Example – Sargassum , Fucus 13/19

14. ISOMORPHIC TYPE In this type there are two exactly similar somatic phases showing alteration of generation. Here the one phase is diploid while the other haploid among chlorophyceae . Example - Ulva 14/19

15. This pattern of life cycle is exactly like isomorphic only with the difference that the alternating haploid and diploid somatic phases are morphologically different. The diploid multicellular sporophytic plant produces haploid zoospores by meiosis. These zoospores develop into gametophytes. HETEROMORPHIC TYPE 15/19

16. HAPLOBIONTIC TYPE Haplo = haploid phase + biontic = two times In this pattern there are three phases in the life cycle. Out of three two phases are haploid and one diploid. The examples are found among Rhodophyceae . 16/19

17. Diplo = Diploid phase + Biontic = two times DIPLOBIONTIC TYPE This type of life cycle is found in almost all Rhodophyceae except Nemalionales . The most common example is Polysiphonia . 17/19

18. REFERENCES BOOKS – THE ALGAL WORLD (SPRINGER ) A TEXT BOOK OF BOTANY VOL. 1 (NCBA) WEB SITES – Sciencedirect.com Researchgate.net Byjus.com http://premabotany.blogspot.com/2018/12/methods-of-reproduction-in-algae-algae.html?m=1 http://premabotany.blogspot.com/2018/12/methods-of-reproduction-in-algae-algae.html?m=1 https://microbiologynote.com/life-cycle-of-algae/ https://www.biologydiscussion.com/algae/4-main-patterns-of-life-cycle-in-algae/46706 18/19

19. THANK YOU 19/19