Cellular Organisation in Plants and Animals

Study Notes

Tissues are a group of cells that have similar structure and function
Plant tissues can be classified into meristematic tissues and permanent tissues
Animal tissues are generally classified based on function

Meristematic tissues are made up of actively dividing cells.
Found at growing points like root tips, stem tips, and branch tips
Characteristics of meristematic tissues:
- Small cells with thin cell walls
- Large and prominent nuclei
- Almost no vacuoles
- Cells actively divide to add new cells
Function: Responsible for primary growth (elongation) and secondary growth (thickness) of the plant.

Apical meristem: Present in root and shoot tips
- Division occurs in different planes
- Increases length of the plant
Intercalary meristem: Located at the base of internodes or leaves
- Responsible for elongation of the plant body
Lateral meristem: Present on the lateral side of the plant body
- Increases the thickness or girth of the plant

Permanent tissues are cells that have stopped dividing
Tissues found throughout the bulk of the plant body
Characteristics: Cells do not divide and remain the same throughout the plant's life
Types of permanent tissues:
- Protective tissue
- Supportive tissue
- Conducting/Complex tissue

Parenchyma:
- Living cells found in soft parts of the plant
- Large, thin-walled cells with intercellular spaces
- Store food materials, like starch in potatoes
- Provide temporary support to the plant
- Some parenchyma cells contain chlorophyll
Collenchyma:
- Found in leaf stalks and below the epidermis of stems
- Elongated cells with thickened corners
- Provides flexibility and support to plant parts
Sclerenchyma:
- Dead cells found in stems and veins of leaves
- Long, narrow, and thick-walled cells
- Provides strength to plant parts

Xylem and Phloem are the two types of conducting tissues
Xylem:
- Made up of thick-walled, tubular, and often dead cells
- Contains tracheids, vessels, xylem parenchyma, and xylem fibres
- Function: Transports water and minerals absorbed by the roots from the soil upwards to the leaves
Phloem:
- Made up of living tubular cells
- Contains sieve tubes, companion cells, phloem parenchyma, and phloem fibres
- Function: Provides a passage for the downward and upward movement of food manufactured in the leaves to various parts of the plant.