Flowering Plants

Introduction to Flowering Plants

Flowering plants are plants that produce flowers

Flowering plants are vascular plants as they contain vascular tissues (both xylem and phloem) 

Flowering plants are seeded plants as they produce seeds.

Flowering plants produce seeds enclosed with fruits.
Flowering plants are also called angiosperms.
Angiosperms are characterized by presence of roots, stems, leaves, flowers and fruits.
The underground part of the flowering plant is the root system while the portion above the ground forms the shoot system.

Figure: Structure of a Flowering Plant

According to the type of seed they produce; flowering plants are classified into: 

1. Dicot plants (dicotyledonous) and 
2. Monocot plants (monocotyledonous) 

Dicot plants produce seeds with two cotyledons while monocot plants produce seeds with one cotyledon

Functions of the Root and Shoot System

Leaves

Plant leaves are green in color as they contain green colored pigment called chlorophyll

Leaves are the photosynthetic organs for green plants.

Figure: Monocot and dicot leaves

External Structure of a Leaf:

Internal Structure of a Leaf

When the leaf is cut in cross-section and seen under a microscope, the below structures are seen:

Figure: Internal structure of a Leaf

Cuticle: 

Cuticle is a transparent waxy layer covered on the upper surface of the leaf
Cuticle is made up of wax which is secreted by the epidermal cells

Functions of the Cuticle

Cuticle allows light to pass into the leaf       Cuticle reduces water loss (acts as a waterproofing of the leaf)       Cuticle protects the leaf from drying out

Epidermis: 
Epidermis is a single layer of cells on the upper and lower surface of the leaf.
The epidermal cells of the leaf don’t contain chloroplast.
Leaf epidermis keeps the leaf’s shape.

Epidermis of the leaf is divided into upper epidermis and lower epidermis

Upper epidermis: 
Upper epidermis is found on the upper surface of the leaf and can be seen when the leaf is cut in cross-section and observed under microscope.
Cells of the upper epidermis are transparent
No stomata are present

Lower epidermis:
Lower epidermis is found on the lower surface of the leaf and can be seen when the leaf is cut in cross-section and observed under microscope.
Stomata are present

Functions of the Upper Epidermis of the Leaf
Allows light to pass into the leaf       Acts as a barrier to micro-organisms       Secretes wax
Functions of the Lower Epidermis of the Leaf
Acts as a protective layer       Site of gaseous exchange into and out of the leaf

Mesophyll tissue: 
Mesophyll is the tissue between upper and lower epidermis of the leaf
Mesophyll tissue consists of:

1. Palisade cells (palisade mesophyll cells) and 
2. Spongy cells (spongy mesophyll cells)