Table of Contents
Life Cycle of Chara – Chara Reproduction
Vegetative Reproduction in Chara
Chara is a green algae that belongs to the Characeae family. It loosely resembles land plants because of the presence of stem-like and leaf-like structures. They are multicellular organisms and thrive in freshwater environments, particularly in the northern temperate zones where they can be seen immersed in water attached to the muddy bottom. They favour less oxygenated water and are not found in waters that have mosquito larvae in it.
Classification
|
Kingdom |
Plantae |
|---|---|
|
Division |
Charophyta |
|
Class |
Charophyceae |
|
Order |
Charales |
|
Family |
Characeae |
|
Genus |
Chara |
Characteristics of Chara
Chara is commonly known as stoneworts because they are covered with calcium carbonate. The structure of Chara is multicellular and profusely branched, and the plant body is divided into rhizoids and a main axis. The most common species found in India include C. braunii, Chara fragilis and C. zeylanica.
Rhizoids
Rhizoids are thin, thread-like structures that are multicellular, uniseriate and elongated in nature. The elongated branches have an oblique septa and they rise either from the base of the plant body or from the peripheral cells of the lower nodes of the main axis.
Main Axis
The main axis of Chara is an erect, long and epigeal structure of the plant body that is differentiated into nodes and internodes.
Internode
The internode is made up of two types of cells:
- Axial cells: They are central, elongated and cylindrical cells.
- Cortical Cells: They are elongated cells that are smaller in diameter than the axial cells. They are present as a layer on the axial cells. They arise from the node. 50% of the cortical cells grow upward and are known as ascending filaments, the rest 50% grow downward and are known as descending filaments.
Node
The node is made up of two cells which are surrounded by 16-20 peripheral cells. Three appendages arise from the node:
- Axillary branches: These are branches of unlimited growth that arise from the older nodes. Also known as long laterals, these branches are also divided into nodes and internodes.
- Primary laterals: These are branches of limited growth that arise in whorls of 6-16 from the branches of unlimited growth. They are also known as branchlets. Each branch is divided into 5-15 nodes and internodes. The node develops secondary laterals that are hair-like unicellular structures. Sex organs arise from the lower nodes of such branches.
- Stipulodes: These are unicellular projections that arise from the lower nodes of branches of limited growth. If the number of stipulodes is equal to the number of branchlets, it is called unistipulate; it is called bistipulate if the stipulodes are doubled in number. If the stipulodes are arranged in a single row, it is known as haplostephanous. However, if the stipulodes are arranged in two rows, it is called diplostephanous.
Refer: Algae – Definition, Characteristics, Types and Examples
Life Cycle of Chara – Chara Reproduction
Chara reproduces vegetatively and sexually.
Vegetative Reproduction in Chara
- Bulbils: Bulbils are small, spherical or oval bodies that develop on the shoot or root nodes of Chara. They detach and germinate into new plants.
- Amorphous Bulbils: Amorphous bulbils are an aggregation of cells that develop at the nodes. They detach and germinate into new plants.
- Amylum Stars: Amylum stars are another type of multicellular aggregation that have a star shape and are filled with amylum starch. They are found in the basal region of nodes.
- Secondary Protonema: Secondary protonema are thread-like structures that are formed in the basal cells of rhizoids. They give rise to new plants.
Sexual Reproduction in Chara
The mode of reproduction in Chara is oogamous. The male sex organ is spherical and yellow to red in colour, called globule. The female sex organ is oval and greenish in colour and called the nucule or oogonium. The sex organs are borne on the branch of limited growth mingled with secondary laterals. The female sex organ, or the nucule is situated singly above the globule.
The species of Chara can either be homothallic or heterothallic.
Structure of Globule
A mature globule is yellow to red in colour and spherical in shape. Each globule consists of outer curved plates called shield cells, eight in number. Each shield cell gives rise to a central rod-shaped structure called a manubrium. The distal end of the manubrium gives rise to a globose-shaped structure called the primary capitula which extends into the secondary capitula.
The secondary capitulum gives rise to antheridial filaments (2-4 in number). The antheridial filaments have 25-250 cells known as antheridium. Each antheridium can give rise to biflagellate, uninucleate and coiled antherozoids.
Structure of Nucule
The nucule, or the female sex organ is an oval structure that is borne on a small stalk. It is made up of one central cell, and a large egg at the top. The whole structure is covered by spirally twisted tube cells, five in number, except at the top. A group of five cells called corona cells is present at the top.
Fertilisation
At the time of fertilisation, the spirally twisted tube cells separate to form five narrow slits. Only one antherozoid can enter the nucule through these slits up to the site of the egg. The antherozoid and the egg fuse to form an oospore.
Germination
At the time of germination, the oospore divides meiotically to form four haploid nuclei. The oopsore is then divided into two unequal cells: an upper lenticular cell with one nuclei and a lower basal cell with three nuclei. The nuclei of the basal cell degenerate eventually. The lenticular cell extends out by rupturing the oospore wall. The extension then divides by mitotic division to form a protonemal initial and a rhizoidal initial. The protonemal initial gives rise to the plant body while the rhizoidal initial gives rise to the rhizoids.
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Also Read:
- What is the Economic Importance of Algae?
- Phycology – Explore the Study of Algae
- Algal Blooms – Everything you Need to Know
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