Key Differences in Plant vs Animal Tissues and 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.
FAQs on Tissues and Cell Diversity in Plants and Animals Explained
1. What are the main types of plant tissues and their functions?
Plant tissues are broadly classified into two main types based on their ability to divide:
- Meristematic Tissue: Composed of actively dividing cells responsible for plant growth. It is found in growing regions like the tips of roots and stems (apical meristem), the sides of stems (lateral meristem), and at the base of leaves or internodes (intercalary meristem).
- Permanent Tissue: These tissues are derived from meristematic cells but have lost the ability to divide. They are differentiated to perform specific functions like storage, support, and transport. They are further divided into simple and complex permanent tissues.
2. What are the four major types of animal tissues?
The four principal types of animal tissues, each with a distinct function, are:
- Epithelial Tissue: Forms the covering or lining for all internal and external body surfaces. It is involved in protection, secretion, and absorption.
- Connective Tissue: Supports, connects, or separates different types of tissues and organs. Examples include bone, cartilage, fat, and blood.
- Muscular Tissue: Composed of cells specialized for contraction, which produces movement. It includes skeletal, smooth, and cardiac muscle.
- Nervous Tissue: The main component of the nervous system, it is responsible for transmitting and processing information through nerve impulses.
3. How do plant and animal cells differ in their typical shape and size?
The primary differences in shape and size are due to structural components:
- Shape: Plant cells have a fixed, often rectangular or polygonal shape because of the rigid cell wall outside the cell membrane. Animal cells lack a cell wall, which gives them a more flexible, irregular, or rounded shape.
- Size: Plant cells are generally larger (10 to 100 micrometres) than animal cells (10 to 30 micrometres). The presence of a large central vacuole in mature plant cells significantly contributes to their overall size.
4. What is the fundamental difference between simple and complex permanent tissues in plants?
The fundamental difference lies in their cellular composition. Simple permanent tissues, such as parenchyma, collenchyma, and sclerenchyma, are composed of only one type of cell that work cohesively. In contrast, complex permanent tissues, like xylem and phloem, are made up of multiple types of cells that coordinate to perform a specialized, collective function like transporting water and nutrients.
5. Why do cells within a single organism exhibit such a diversity of shapes and sizes?
The diversity in cell shape and size is a direct result of the biological principle of 'form follows function.' Each cell is specialized for a particular job, and its structure is optimized for that role. For example, nerve cells are long and branched to transmit signals effectively, while red blood cells are small and biconcave to maximize oxygen-carrying capacity and squeeze through tiny capillaries.
6. Why is blood considered a type of connective tissue?
Blood is classified as a fluid connective tissue because it meets the key criteria for this group. It consists of various living cells (red blood cells, white blood cells, and platelets) suspended in a non-living, extracellular fluid matrix called plasma. Its primary function is to connect different body systems by transporting oxygen, nutrients, hormones, and waste products, thereby linking all parts of the organism.
7. What is the importance of staining tissues before observing them under a microscope?
Staining is a crucial step in microscopy because most biological tissues and their cellular components are nearly transparent and colourless. Stains are special dyes that bind to specific structures within the cells and tissues, adding colour and increasing contrast. This makes it possible to distinguish different cell types, organelles, and the overall tissue structure, which would otherwise be invisible.
8. What is histology and why is it important in biology?
Histology is the branch of biology concerned with the study of the microscopic anatomy of cells and tissues in plants and animals. Its importance lies in revealing how cells are organised to form tissues and organs. This understanding is fundamental to physiology (how bodies function) and pathology (the diagnosis of diseases), as changes in tissue structure are often indicators of illness.
9. How do meristematic tissues allow plants to grow throughout their lives, a feature largely absent in animals?
Plants possess meristematic tissues, which are equivalent to stem cells in animals but are concentrated in specific zones (meristems). These cells remain undifferentiated and can divide indefinitely, enabling continuous (indeterminate) growth in length and girth. Most animals undergo determinate growth, reaching a fixed adult size. While they have stem cells for repair and regeneration, they lack the organised, persistent growth zones that allow for lifelong increases in overall body size like plants.
10. Can you provide an example of where parenchyma, collenchyma, and sclerenchyma tissues are found in a plant?
Certainly. These simple permanent tissues are found in different locations based on their function:
- Parenchyma: This is a packing tissue found in the soft, fleshy parts of a plant, like the cortex of stems and roots, and the mesophyll of leaves where it performs photosynthesis.
- Collenchyma: Provides flexible support and is typically found just beneath the epidermis in young, growing stems and in leaf stalks (petioles).
- Sclerenchyma: Offers rigid, mechanical support. It is found in the hard husk of a coconut, the gritty texture of pear fruit, and surrounding vascular bundles.
