Botany lecture notes

Polysiphonia: Thallus Structure, Reproduction, Post Fertilization Changes and Life Cycle

Polysiphonia Post Fertilization Changes

(Thallus Structure, Reproduction, Post Fertilization Changes and Life Cycle)

Polysiphonia- Systematic Position

Division: Rhodophyta
Class: Rhodophyceae
Order: Ceramiales
Family: Ceramiaceae

Distribution of Polysiphonia

Ø  Polysiphonia is marine red algae belongs to the class Rhodophyceae.

Ø  They are abundantly present in the Atlantic Coasts of America.

Ø  Polysiphonia platycarpa is present in the Indian coastal regions.

Ø  Polysiphonia violacea is an epiphytic alga grown on some brown algae such as Fucus vesiculosus.

Ø  Some species of Polysiphonia are parasitic (example: Polysiphonia fastigiata).

Thallus Structure of Polysiphonia

Ø  As the name suggests, the thallus of Polysiphonia is siphonous with many interconnected filaments (siphons).

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Botany lecture notes

Pigments in Algae (Key points) with PPT

pigments in algae

Pigmentation in algae:

Ø  Algae show great diversity in pigmentation.

Ø  Many coloured pigments such as green, red, yellow, and blue have been found in marine and freshwater algae.

Ø  Different groups of algae have different and specific pigment composition.

Ø  Pigments are usually found in specialized plastids called chromophores in all groups of algae except in the members of Cyanophyceae (blue green algae).

Ø  Distribution pattern of pigments has great taxonomic significance in algal systematics.

Ø  Classification of algae proposed by Fritsch is primarily based of the pigmentation of algae.

Ø  All major algal groups have at least one characteristic pigment in their cells.

Pigments in algae belong to THREE major categories based on their physical and chemical properties.

(1). Chlorophylls

(2). Carotenoids

(3). Phycobilins

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Botany lecture notes

Life Cycle in Algae (Haplontic, Diplontic, Haplodiplontic, Haplobiontic and Haplo-diplobiontic Life Cycles)

Life Cycle of Algae

Nature is a machine. The family is a machine. The life cycle is like a machine.

Ray Dalio

What is life cycle?

The growth and development consists of a number of distinct morphological and cytological stages. The sequence of these orderly changes is called as LIFE CYCLE. It is the sequence of all different phases or events through which an organism passes from a diploid zygote of one generation to the zygote of the next generation through haploid gametes.

There are five different types of life cycles in algae based on the number of haploid and diploid generations.

life cycle in algae

Haplontic Life Cycle

1. Haplontic life cycle

2. Diplontic life cycle

3. Haplodiplontic life cycle

4. Haplobiontic life cycle

5. Haplo-diplobiontic life cycle

(1). Haplontic life cycle:

Ø  Most common type of life cycle in algae

Ø  Life cycle is diphasic (two phases)

Ø  The prominent phase is haploid gametophytic phase

Ø  The diploid (sporophytic) phase in the life cycle is represented by the ZYGOTEContinue reading

Botany lecture notes

Algae: General Characters (with Power Point Presentation – PPT)

Important Characteristics of Algae


“The life of the planet began the long, slow process of modulating and regulating the physical conditions of the planet. The oxygen in today’s atmosphere is almost entirely the result of photosynthetic living, which had its start with the appearance of blue-green algae among the microorganisms”

                                                                     Lewis Thomas, 1984

General appearance of algae

An Algal Bloom of Blue Green Algae

What are algae?

Algae is a group of chlorophyll containing thalloid plants which bear unicellular or multicellular sex organs and the sex organs are NOT protected in the sterile jacket cells. An undifferentiated plant body is known as ‘thallus’. In thalloid plants, there is no differentiation of plant body into true roots, stem and leaves.

The study of algae is known as PHYCOLOGY. The one who study algae is called Phycologist

General characters of algae

Ø  Thalloid plant body

Ø  In Eichler’s system of classification, algae are placed in the Division Thallophyta along with Fungi and Lichens.

Ø  Algae are autotrophs (synthesize food using light energy)

What is thallus?

Spirogyra Thallus *

Ø  Algae differ from fungi in:

⊕. Presence of photosynthetic pigment – chlorophyll
⊕. Mode of nutrition (autotrophs)

Ø  Majority of algae are in aquatic habitat (fresh water or marine), some algae are terrestrial also

Ø  Algae are present in all parts of the world including Arctic and Antarctic regions (universal occurrence)

Ø  Sex organs are unicellular or multicellularContinue reading