This document summarizes the perennation and life cycle patterns of algae. It discusses various perennation structures that allow algae to survive unfavorable conditions, such as akinetes, mucilaginous sheaths, palmella stages, aplanospores, and resting spores. It also describes the three main life cycle patterns seen in algae: haplontic, diplontic, and haplodiplontic. Haplodiplontic life cycles can be biphasic with isomorphic or heteromorphic phases, or triphasic with haplobiontic or diplobiontic patterns. Examples of different algae are provided for each life cycle type.

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.
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3.  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
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4. :
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
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5.  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
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6.  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
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7. 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
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8. 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.
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9.  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.
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10.  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
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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 :
1. Haplontic type
2. Diplontic type
3. Haplodiplontic type :
A. Biphasic
i. Isomorphic type
ii. Heteromorphic type
B. Triphasic
i. Haplobiontic type
ii. Diplobiontic type
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12. 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
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13. 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
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14.  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
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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.
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16. 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.
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17. Diplo = Diploid phase + Biontic = two times
This type of life cycle is found in almost all Rhodophyceae except Nemalionales.
 The most common example is Polysiphonia.
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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
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19. THANK YOU
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