Cells, Tissues and Organs

CELLS, TISSUES & ORGANS

Introduction
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Cells are the basic units of all living things. A tissue is an group of cells that work together to carry out a specific function*

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An organ is a collection of tissues joined in structured units to serve a common function. Cells Tissues Organs

TYPICAL STRUCTURE OF A DICOTYLEDONOUS ROOT

CELLS

CELLS
The dicotyledonous root consists of the following cells:  Epidermal Cells  Parenchyma Cells
Other cells of the plant include:  Schlerenchyma  Collenchyma

TISSUES OF THE PLANT

TISSUES

TISSUES
There are three main types of tissues:  Dermal Tissue  Vascular Tissue  Ground Tissue

DERMAL TISSUE (AKA Epidermis)
Functions:  Protects against water loss  Regulates gas exchange  Secretes metabolic compounds  Absorbs water and mineral nutrients. (especially in roots)

VASCULAR TISSUE (Transportation)
Function:  Transport materials that are essential for plant survival, between the roots and shoots.

GROUND TISSUE
Functions:  Storage  Photosynthesis  Support etc.

THE CORTEX
Is the region of the root located inside the epidermis

HYPODERMIS (AKA Exodermis)
Function:  Prevent water and minerals from leaking through the cortex  Prevent the entrance of microorganisms

STORAGE PARENCHYMA
Function:  Stores starch and other substances

ENDODERMIS
Function:  Regulates the passage of water and dissolved substances by forcing them to move through living plasma membranes and plasmodesmata* and not simply diffuse through the porous cell walls. *Plasmodesmata are narrow extensions of cell sap
between cell walls.

DIAGRAMS OF THE ENDODERMIS AND THE FLOW OF MATERIALS THROUGH THE CASPARIAN LAYER

THE STELE

PERICYCLE
Fuction:  Regulates the formation of lateral roots

XYLEM & PHLOEM
Function:  Transportation of materials throughout plant

CAMBIUM
Function:  Produce new phloem on the outside and xylem on the inside in roots, stems etc.