Structure of Volvox Colony, Sexual and Asexual Reproduction in Volvox (With Diagrams)

After reading this topic you will learn about Habitat, Structure of Colony, Sexual and Asexual Reproduction in Volvox


Volvox is found in both in freshwater and marine water. Its presence gives water green color. It appears both in spring and summer season but mostly grow in rainy season. Season also affect on Sexual and Asexual Reproduction in Volvox.


Volvox always live in colony.

The cells of volvox colony are always fixed so that is called coenobium.

Spherical in shape. The rang of each colony cells from 500-50,000.

The outside of the colony consists of mucilage.

Volvox cells have biflagellate. Flagellate found outside of colony.

The collective movement of the flagella help to move the colony.

The shape and structure of all cells of a colony have alike.

The cell is closely packed. They are organized to form polygonal shape in the volvox colony.

The mature cells wall is thick & mucilaginous.

Their cell looks like pear shaped. These cells make periphery around the colony.


The structure of volvox same as Chlaymydomonas.

 Every cell has Biflagellate and attached at the outer side of the cells.

Each cell has cup shaped chloroplast. Chloroplast have one pyrenoid.

They have two contractile vacuoles that help in maintain the water balance in cell.

A nucleus found in center of cell and connected with flagella by neuromotor.

It also has eyespot near the anterior surface of colony that help in swimming in light.

Structure of volvox Colony

REPRODUCTION (Sexual and Asexual Reproduction in Volvox):

In volvox both type of reproduction present such as asexual and sexual.


Asexual reproduction occurs when condition is favorable.

Already present colonies reproductive cells help to produce new colonies.

Only posterior side of cell take part to make new colony by asexual reproduction

The cells increase in size. They are larger in size. These are known as gonidia.

These Gonidia develop in to many pyrenoids.

There are 5 to 20 gonidia in each colony.

Each gonidia produce daughter colony.

Sexual and Asexual Reproduction in Volvox


The gonidia move towards interior side of the colony. The first step gonidium divide longitudinal and this forms two cells.

In second step of division cell also divide longitudinal at right angle to the first into four cells.

 The third step four cells divide longitudinal and make eight cells from four cells are central.

These eight cells arranged in curved like structure that structure is called plakea stage.

These eight cells future longitudinal divide and make 16 cells.

These arrangements look like hollow-sphere.

This hollow sphere open on exterior side as a small hole that’s called phialopore.

The cells continue divide until the cells reaches the distinctive of that species.

The last step is inversion of colony. The cells become opposite in direction, their anterior end must face the periphery of colony.

Thus, new colony comes out from paternal cells.

Sometimes it remains within the parent colony.


Sexual Reproduction Occur When Condition Are Unfavorable.

The Oogamous type of Sexual reproduction mostly present in volvox. Colony may be monoecious or dioicous.

Female gametes known as gyn gonidia and male gametes are called antheridia.

these reproductive cells commonly called gametangia.


The male part (gametangia) are called antheridium. The antheridium. protoplast of divides many times like asexual reproduction. It divides again and again and produces 16-128 cells. These cells named antherozoid.

When division was compete they develop new flagellum at ends point of cells.

Types of Antherozoids:

There are two types of  Antherozoids cycles:

a)       When cells are 128 or less after division. In this type, all the antherozoids colony are liberated in the form of mass, Mass swims and reaches to the oogonium. Then the cells of antherozoid gets detached.

b)       If cell divide more than 128. In this type, antherozoids call become arranged itself into a hollow sphere shape within the antheridium. These cells undergo inversion process. After inversion antherozoids cells separate from each other. Then they are liberated fertilization.


Then female reproduction organ is Gynogonidia or oogonia. Female sex part is larger than male sex part. The protoplast of female converts into single oosphere in rounded in shape.


 The male part (Antherozoids) enter oogonium through a pore. Only single antherozoid enter in female sex and zygote is formed. When Zygote formed it secretes a thick wall that become oospore. This wall consists of three layered. Oospore produces a secretion in large amount that called heamotochrome, due to this its color orange red. They release oospore and in favorable condition they germinate same as asexual reproduction.

Key Difference Between Prokaryotic cell and Eukaryotic cell with Label Diagram?

Difference Between Prokaryotic cell and Eukaryotic cell :

Difference Between Prokaryotic cell and Eukaryotic cell. Cell is the basic structural and functional unit of all the living organism except virus. A single cell is composing of a protoplasm a boundary the member and genetic material. Cell consists of many organelles. Organelles make a special structure of cell and help the cells to perform many functions. There are two types of organelles. One is membranous Organelles and second is Non-membranous Organelles.

On the base of organelles cell is divide into two Group. e.g. Prokaryotes and Eukaryotes.


Prokaryotes are group of those organism that make up of Prokaryotic cells. Prokaryotic cells are very primitive cell in morphological point of view. There have no well defined nucleus and many major organelles such as Golgi complex, endoplasmic reticulum, mitochondria and centriole etc.

In other word you can say prokaryotic cells have no membrane bound organelles. In Prokaryotic cell genetic material (chromosome) is bounded in a portion of cytoplasm that called nucleoid.


Eukaryotes are group of those organism that make up of Eukaryotic cells. Eukaryotic cells consist of plasma membrane and membrane bounded organelles such as Golgi complex, endoplasmic reticulum, mitochondria and centriole etc. They have well defined nucleus.

 In animals and plant various types and shape of cells exhibit. In animals mostly, cells are spherical in shape, in plants its shape is rectangular. The shape of cells differs from animal to animals. There is a correlation between the size, shape of the cell according to their function.

Difference Between Prokaryotic cell and Eukaryotic cell with Label Diagram

Key Difference Between Prokaryotic cell and Eukaryotic In Table

Feature Prokaryotic cell Eukaryotic cell
Cell Size Prokaryotic cell have On an Average Diameter 0.5-5 um.Up to 40 um in diameter, it 1000-10000 more from prokaryotic.
FromUnicellular or filamentous in form. Unicellular or truly multicellular in nature.
Genetic MaterialNo true nucleus present in it. DNA laying naked in cytoplasm. True nucleus present in it. DNA associated within the protein.
Protein SynthesisSmaller Ribosome (70s). No endoplasm recticul involve for protein synthesis.Lager Ribosome (80s). This ribosome attach with ED.
organellesFew organelles are present . They have no member outside (Non membrane bounded organelles).Many organelles are founded.All organelles are membrane bounded. such mitochondria, Golgi complex etc.
Cell WallRigid and compose with amino acid and polysaccharide. Murine is the main component of cell wall they strentn to cell wall.Cell wall of fungi and plant are rigid and compose of polysaccharide material.cellous is the main component of cell wall that give strength to plant and chitin is main component of fungal wall.
Flagella Very simple not cover by any membrane and microtubule also absent in it. The size 20um. Complex in nature, 9+2 arrangement of microtubules are occurred. Its cover by outer membrane. Its diameter is 200um.
In bacteria respiration occur through mesosoma, except cytoplasmic membrane in blue green algae.
In which aerobic respiration through mitochondria .
PhotosynthesisChloroplast is absent. Photosynthesis occur through member which show no stacking.
Chloroplast is present in member which have stack of grana.
Nitrogen FixationFew Have the ability to fix the nitrogen.No one have the ability to fix Nitrogen.

What is Advantage and Disadvantage of Transpiration?

Transpiration Is a necessary Evil

Transpiration is a process in which plants lose water through the leaves or stomata. 
It is well-thought-out as an evil because extreme loss of water tend to stop the photosynthetic process and close the stomata. Advantage and disadvantage of transpiration tell the value of this event in plant life.

Advantage and Disadvantage of Transpiration

According to following respect transpiration are harmful.

Disadvantage of Transpiration:

  1. Water is most important component of plant. They utilize large amount of energy to get water from the soil and transpiration cause loss of energy in plant.
  2. Under water deficiency condition transpiration cause wilting, desiccation and mostly cause death of plants.
  3. In deciduous plants they shed their leaves to prevent water from loss and stop transpiration.
  4. In inadequate water supply plants wilt and their leaves become dry up especially older leaf.
  5. Mostly growth stunted due to high loss of water.
    Above all discussion suggest that transpiration is an Evil, some biologist say that transpiration is a necessary evil. The study of plants leaves show that stomata are primary organ that exchange the gases form the atmosphere, so this process cannot be avoided. So, they consider that transpiration is important for metabolic activity in plant. Transpiration have some advantage.

Advantages of Transpiration:

  1. Absorption of water and its translocation
  2. Absorption of minerals and their Distribution
  3. Energy exchange
  4. Improving quality of fruit
  5. Development of mechanical tissue in plant
  6. Optimum Turgidity

Absorption of water and its translocation:
In plants root absorbed water form soil through osmosis and use for transpiration. Transpiration pull help in absorption of water and upward movement in plant. In this way water stream is establish from root to top.

Absorption of minerals and their Distribution:
Mineral absorption is an active process and mineral supply is more at night as compare to day. According to some worker salt and mineral supply is passive under the influence of transpiration pull.

Energy exchange:
Heat energy in harmful for cell and leave absorbed 65% of sunlight that full on leaves, therefore get warmed. Transpiration is a cooling process and each gram of 2.4 KJ from the leaf and its environment. They also help in dissipate the absorbed radiant energy.

Improving quality of fruit:
Higher the rate of transpiration increasing the carbohydrates content of the fruit. Such fruit have a higher dry matter content that had a greater supply of water.

Development of mechanical tissue in plant:
More transpiration more development of mechanical tissue that help the plant resist form mechanical injury, stockier and tougher. The cell wall thick and cutinized that make plant more resistance to bacteria and pathogenic.

Optimum Turgidity:
It observed that more plants need Optimum Turgidity for best cell function. The over and under turgidity condition not helpful for cell growth. Transpiration help to maintain the Optimum Turgidity.

Define Transpiration, Types and Factor that affect Transpiration Rate


Transpiration is a loss of water from the plants surface/aerial parts of the plants in the form of vapor. Water move outside through stomata, cuticle layer and lenticels in the leave.

Types of Transpiration:

Based on sites for water loss it classified into following types.

  1. Stomatal transpiration
  2. Cuticular transpiration
  3. Lenticular transpiration


Stomata are elongated slit like pores in epidermis surrounded by kidney shaped guard cells. In monocots and in few dicots the guard cells are covered by some subsidiary cells which are differ from epidermal cells. They help the stomata opening and closing. Stomata are openings pores in plant structure that exchange gas.

Stomata are usually found in plant leaves however may also be found in stems. A specialized cells referred to as guard cells surround stomata and control open and closing of stomatal pores. Stomata permit a plant to require in greenhouse emission, that is required for chemical process.

Plants have thousands of stomata on the surfaces of their leaves. the bulk of stomata are placed on the side of plant leaves reducing their exposure to heat and weather condition. In aquatic plants, stomata are placed on the side of the leaves. A stomata is specialized plant cells. They consist of guard cells and subsidiary cells.

These cells enlarge and contract to open and shut stomatal pores. Guard cells additionally contain chloroplasts, the light-capturing organelles in plants.

Subsidiary cells surround and support guard cells. They act as a buffer between guard cells and stratum cells, protective stratum cells against guard cell growth. Subsidiary cells varied exist in various shapes and sizes. they’re additionally organized otherwise with relevance their positioning around guard cells.

Guard Cells:

These cells are thick walls and differ from some other leaf cells. These are more thickened as compare to dorsal wall. The thinking is due to the cellulose microfibrils in the guard cell and help in the closing and opening of stomata. Kidney shaped guard cell the cellulose microfibrils fan out radially from pores, thus the cell girth is reinforcing like a steel belted radial tire, and the guard cell curve out to widen the stomata pore.

Theories Explaining opening and closing of stomata:

  1. Photosynthesis in Guard Cells
  2. Starch Sugar Interconversion hypothesis of Stomata Movements
  3. Active K+ ion Transport and Hormonal Regulation Theory

Photosynthesis in Guard Cells:

These cells consist on chloroplasts, they synthesize glucose during day time that increase the osmatic potential in guard cells and increase turgor pressure. At night time the glucose converts into starch and osmotic potential of guard cells decrease and stomata become close. In guard cell protoplast lack of enzyme that use for reduction of carbon dioxide that lead to the formation of sugars. In CAM plant, during night stomata open and photosynthesis is absent.

Starch Sugar Interconversion hypothesis of Stomata Movements:

According to some scientist at night starch content increase at night time in guard cells so they close at night. Therefore, it was suggested that in the presence of light starch convert into glucose.

Similarly, stomata are very sensitive to pH. The low pH closer the stomata and high pH open the stomata.  In the presence of light pH increase and starch convert into glucose. In dark this process is reverse. They pH change are brought by co2, carbon dioxide increases the pH and convert starch into glucose.

The presence of glucose 1- phosphate and phosphorylase enzyme in guard cell that convert starch into glucose is brought by phosphorylase. At pH 7 the starch is converting to glucose 1-phosphate and at about pH 5 starch is synthesis. The glucose 1-phosphate is converting into glucose 6-phosphate and then spilt into glucose and phosphate. The glucose dissolve and osmatic potential is increase in guard cell. At nigh this process is reverse.

 Active K+ ion Transport and Hormonal Regulation Theory:

The accumulation of k+ and carbon dioxide increase in guard cell during day time in the presence of light and revers in night. At (400-800mM) the concentration of k+ is increase and stomata open and close at (100mM). The change in starch concentration increase the k+ ion concentration.

The starch concentration was found to decrease in the presence of light when stomata are open and increase in dark when stomata are close. It considers that light stimulates guard cell to accumulate potassium and become turgid.

This response triggered by illumination of a blue light receptor in the guard cell, perhaps built into the plasm membrane. Activation of these blue light receptors stimulates the activity of ATP powered proton pumps in the plasma membrane of guard cell, that increase the concentration of k+.

Process of Synthesis K+ Malateion:

Presence of light pH increase, carbon dioxide concentration decreased, and starch is converting into 3-C compound (phosphenolpyruvic acid) PEP. This 3-C compound combine with carbon dioxide and convert into oxalic acetic. Oxalic acetic is convert into malice acid. Malice acid is a week acid they break down into H+ and Malate ions. K+ and malate ions combinedly make potassium malate that increase solute in guard cell and lower water potential. Thus, water enter guard cells. At night this process become reverse.

Factor Affecting the rate of transpiration:

The rate of transpiration is affected by both external and internal factor. These factor effect on the stomata opening and closing.

Environmental Factor (External Factor):

  1. Vapour pressure (Humidity)
  2. Temperature
  3. Wind (Air Movement)
  4. Atmospheric Pressure
  5. Light
  6. Availability of soil water

Plant Factor (Internal factor):

  1. Ratio of Root and shoot
  2. Leaf surface area
  3. Leaf structure
  4. Type of cuticle layers
  5. Number of stomata on plants leaf

Function of Roots in plants and Its Anatomy With Diagram


Roots are the part of all plants, its lies below the ground. Its branches profusely to form root system that anchors the plant into the soil and main function of roots in plants absorbed water and minerals from the soil solution.

The outer walls of roots are thine wall hair like structure and elongate cells is called root hair.

Their thin wall helps to absorbed maximum water and most water enter in the plant through roots hair.

The root hair increases the surface area of plant in soil.

In its simplest type, the term root refers to the abstraction of a plant’s rootage. This may be very complicated and depends upon multiple factors like the species of the plant, the composition of the soil and therefore the accessibility of nutrients.

Function of Roots in plants :

The root systems serves to structurally support the plant, contend with alternative plants and for uptake of nutrients from the soil.

Roots grow to specific conditions, which, if changed, will impede a plant’s growth. for instance, a rootage that has developed in dry soil might not be as economical in flooded soil, however plants ar able to adapt to alternative changes within the atmosphere, like seasonal changes.

Growth from top meristems is understood as primary growth, that includes all elongation.

Secondary growth happens at the lateral meristems, specifically the tube-shaped structure cambium and cork cambium. the previous forms secondary vascular tissue and secondary, whereas the latter forms the periderm.

Anatomy of Roots / Structure of Roots in plants :

The center of roots consists of Xylem. Xylem conduct water form soil to plants leaves with the help of roots hair.

Roots plays the necessary role of providing a secure provide of nutrients and water likewise as anchorage and support.

  1. Xylem conducting element is vessels and tracheid’s.
  2. Xylem of the root is continuous with the xylem tissue in the stem.
  3. Xylem closely attached to the phloem cells.
  4. Xylem and phloem are collectively called vascular tissue.
  5. That are cover by a protecting layered that called pericycle.
  6. Pericycle and vascular tissue collectively called Stele.
  7. Just outside the stele layers that’s called endodermis.
  8. Endodermal cells are covered with a thickening wall called Casparian stripe.
  9. Casparian stripe are impermeable to water.
  10. Due to this dissolved substance cannot pass through endodermal.
  11. Out side the endodermis many layers of thin walled of living cell with intercellular space called cortex.
  12. These are very important for aeration.
  13. These cells are permeable to dissolve substance and water.

Pathways for Movement of water and solutes in Plants:

  1. Apoplast Pathway
  2. Symplast Pathway
  3. Vacuolar Pathway

Apoplast Pathway:

Movement of water between the cells of a plants is called Apoplast movement of water.

According to munch interconnected cell wall and water filled xylem element should be consider as single system that called apoplast.

Apoplast pathway used in plants where air space is present. More than 50% cellulose wall have free space. These can be occupied by water and provide efficient channel for the movement of water.

Symplast Pathway:

The movement of water within the cell of plants that called symplast Pathway.

Symplast is the movement of water through the interconnected protoplasts.

The cytoplasm of each cells is interconnected with each other. This movement is occurred in endodermal are where casaparine strip are present. Symplast is important mechanism for plant growth.

Vacuolar pathway:

According to some author central vacuoles conduct the symplast movement. They are independent pathway for the movement of water. In this movement water move from vacuole to vacuole through cells. Its move down a water potential gradient.

Factor Affecting Absorption of Water:

There are two types of factor that effect the absorption of growth.

Soil Factor Affecting Absorption of Water:

  1. Soil Temperature
  2. Aeration
  3. Solute Potential of soil solution
  4. Availability of water

Plant Factors Affecting the absorption of water:

  1. Root System
  2. Transpiration
  3. Metabolic activity