Study of Tissues and Diversity in Shapes and Sizes of Plant and Animal Cells

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.

 

Properties

Parenchyma

Sclerenchyma

Collenchyma

Cell wall

Thin

Thick

At the corners, thick primary wall

Intercellular space

Many

Absent

Absent

Nature of cells

Living. Presence of nucleus

Celled. Absence of cellular contents

Living. Nucleus observed

Shape

Oval, polygonal, spherical, rod-shaped or rectangular

Elongated

Variable shape

Cell arrangement

Arranged loosely

Absent

Absent

Vacuoles

Vacuolated cells

Absent

Compactly arranged

FAQ (Frequently Asked Questions)

Q1. What are the Types of Animal Tissues?

Ans. The four basic types of animal tissue are:

  • Epithelial tissue consists of layers of tightly packed cells that line the surfaces of the body for protection, secretion, and absorption.

  • Muscle tissue is made up of cells containing contractile filaments that move past each other and change the size of the cell. There are three types of muscle tissue: smooth muscle which is found in the inner linings of organs; skeletal muscle, which is attached to the bone and moves the body; and cardiac muscle which is found only in the heart.

  • Nervous tissue is made up of the nerve cells or neurons that together form the nervous system, including the brain and spinal cord.

  • Connective tissue can be densely packed together or loosely packed and is made up of many different types of cells that are all involved in the structure and support of the body. 

Q2. What are the Types of Plant Tissue?

Ans. Basically, it can be classified into two tissues – Meristematic tissue and Permanent tissue.

  • Meristematic Tissue- Meristematic tissues are a group of living cells that are in a specific location and divide continuously to add new cells to the plant body. It can be further classified into:

  1. Apical meristem - It is found in the growing tips of stems and roots and it helps to increase the length of the stem and root. 

  2. Lateral meristem - This meristem is made of cells that mainly divide into one plane and cause the organ to increase in diameter and growth. 

  3. Intercalary meristem - This meristem is found between permanent tissues.

  • Permanent Tissue- Permanent tissues are a group of (living or dead) cells formed by meristematic tissue and cannot divide. It is permanently placed at fixed positions in the plant body. It is of three types- simple permanent tissues, complex permanent tissues, and special or secretory tissues