Definition Structure Types and Functions of Plant and Animal Tissues and Cell Shape Variations
Aim of the Experiment
To study the one-of-a-kind tissues and variety in sizes and shapes of animal and plant cells such as guard cells, palisade cells, parenchyma, sclerenchyma, collenchyma, phloem, xylem, squamous epithelium, mammalian blood smear, and muscle fibers via the training of permanent/brief slides.
Theory
What is Tissue?
A tissue is an ensemble or cluster of similar cells that perform a shared function that is similar in shape and size.
Tissues Can be Classified as –
Simple Tissue – It consists of only one type of cell. And can be classified into:
a) Parenchyma
b) Collenchyma
c) Sclerenchyma
Complex Tissue – Complex tissue possesses more than one cell type.
a) Meristematic tissue –
b) Permanent tissue – It can be further classified as- Simple permanent tissue, complex permanent tissue, and special or secretory tissue
What is a Cell?
Before moving further, it is necessary to define a cell in a single line. Simply, a cell is a basic building block or structural, functional, and biological unit of all living organisms.
Requirements
A. Permanent Slides of:
T.S of Nerium Leaf, T.S of Lotus leaf, T.S of Lotus stem/petiole
V.S of root apex and shoot apex
T.S of Mentha/Cucurbita stem
Macerated material of Tridax, Vitis/Bougainvillea
B. Things Required for Maceration Technique
Tiny twigs of locally accessible plants
Safranin
Glycerine
Beaker of 100ml or Boiling test tube
Slides
Cotton blue
Glass rod
Burner
Tripod stand
Needless
Wire gauge
Microscope
Knife with sharp-edged
Thread
Cheese/muslin cloth
Requirements for Maceration Fluid
Chromic acid should be dissolved with an equal quantity of 10% nitric acid.
Preparation of chromic acid is done by adding 100ml of concentrated H2SO4 gradually in 10ml of water.
Now add K2Cr2O7 (potassium dichromate) – 50gm
The stock solution is ready. 10ml of this solution is diluted up to 100ml for the preparation of the working solution of the maceration liquid.
Procedure
Bring some fine green fresh and younger branches from a locally accessible woody plant. Thickness must be of a toothpick.
Snip the twigs into smaller bits of 0.5cm long.
Put the pieces of twigs to the beaker holding water. Boil it for 10-15minutes till the sample settles down at the base.
This way the air inside the sample will be removed.
Then transfer the material into a beaker having the maceration fluid. Boil it until it turns pulpy and soft for at least to 10-15 minutes.
Put muslin cloths to the beaker's mouth. With tap water, rinse the material continuously to remove the traces from the maceration fluid.
Now add some drops of safranin to the material to stain the xylem or the phloem – cotton blue.
place the stained material in a drop of glycerine into a glass slide.
Split the cells using two needles.
Plant a coverslip onto the slide and observe under a microscope.
Sketch and Compare your observation with the diagram given.
Analyze the Following Slides:
For palisade and spongy tissue – T.S of Nerium Leaf
For Aerenchyma – T.S of Lotus petiole. Lotus leaf
For meristem – V.S of root and shoot apex
For simple tissues – T.S of Menthe stem or Cucurbita
Observation:
Chlorenchyma is parenchyma cells with chloroplasts. They may have spongy or loosely arranged cells or palisade – columnar cells compactly aligned.
If there is a presence of large intercellular spaces into the cells it is aerenchyma.
The protective tissue or the epidermis is the parenchyma tissue forming the outer covering of leaves, stem, or root.
Observe the section of the leaf.
Mesophyll of the leaf is covered by lower and upper epidermis.
Lower epidermis produces small pores known as stomata. In some plants, both the lower and upper epidermis of the leaf show stomata.
Tissues are observed for their characteristics, position in the different parts of the material of the plant.
Sketch diagrams to display the tissue type and their locations.
FAQs on Study of Tissues and Diversity in Shapes and Sizes of Plant and Animal Cells
1. What is the study of tissues in biology?
The study of tissues in biology is called histology, which deals with the microscopic structure and organization of tissues in plants and animals.
In the study of tissues:
- A tissue is a group of similar cells performing a specific function.
- Plant and animal tissues are classified based on structure and function.
- Histology helps in understanding growth, repair, and functioning of organs.
2. What is a tissue and why is it important?
A tissue is a group of similar cells that work together to perform a specific function in an organism.
Tissues are important because:
- They provide division of labour in multicellular organisms.
- They increase efficiency by specializing in particular tasks.
- They form organs and organ systems.
3. What are the main types of plant tissues?
The main types of plant tissues are meristematic tissues and permanent tissues.
They are classified as:
- Meristematic tissue – actively dividing cells responsible for growth (apical, intercalary, lateral).
- Permanent tissue – mature cells that have lost the ability to divide (simple, complex, protective).
4. What are the four main types of animal tissues?
The four main types of animal tissues are epithelial, connective, muscular, and nervous tissues.
They function as follows:
- Epithelial tissue – covers and protects body surfaces.
- Connective tissue – supports and binds other tissues (e.g., bone, blood).
- Muscular tissue – enables movement.
- Nervous tissue – transmits nerve impulses.
5. Why do plant and animal cells differ in shape and size?
Plant and animal cells differ in shape and size because their structure and function vary according to their roles in the organism.
Key reasons include:
- Presence of a rigid cell wall in plant cells, giving them a fixed shape.
- Absence of a cell wall in animal cells, making them flexible.
- Different functional adaptations, such as elongated nerve cells for impulse transmission.
6. What causes diversity in the shapes and sizes of cells?
The diversity in shapes and sizes of cells is caused by functional specialization and adaptation to specific roles.
Examples include:
- Red blood cells – biconcave shape for efficient oxygen transport.
- Muscle cells – elongated for contraction.
- Guard cells – kidney-shaped to regulate stomatal opening.
7. What is the difference between meristematic tissue and permanent tissue?
The main difference between meristematic tissue and permanent tissue is that meristematic cells actively divide, while permanent cells have lost the ability to divide.
Key differences:
- Meristematic cells are small, thin-walled, and densely packed.
- Permanent cells are larger, differentiated, and perform specific functions.
- Meristematic tissue causes plant growth, while permanent tissue supports and conducts materials.
8. How does the structure of a cell relate to its function?
The structure of a cell is closely related to its function, meaning each cell’s shape and organelles are adapted to its role.
Examples:
- Nerve cells have long axons to transmit impulses over long distances.
- Sperm cells have a flagellum for movement.
- Root hair cells have extensions to increase surface area for absorption.
9. Can you give examples of different shapes of plant and animal cells?
Yes, plant and animal cells show a wide variety of shapes depending on their function.
Examples include:
- Parenchyma cells – usually oval or spherical.
- Guard cells – kidney-shaped.
- Red blood cells – biconcave disc-shaped.
- Neuron – long and branched.
10. Why is the study of tissues important for understanding multicellular organisms?
The study of tissues is important because it explains how cells organize into functional units in multicellular organisms.
Understanding tissues helps to:
- Explain division of labour in complex organisms.
- Understand formation of organs and organ systems.
- Study growth, repair, and disease processes.
