FLOWERING PLANTS
These are plants that bear flowers. They belong to the phylum or division- spermatophyta and class
angiosperms.
A typical flowering plant is composed of two systems namely;
1. Shoot system.
2. Root system.
The two systems are composed of two categories namely;
a) Reproductive organs-which are the flowers that produce fruits containing seeds.
b) Vegetative organs-these organs are not directly involved in reproduction. They include roots
stems and leaves.
STRUCTURE OF A FLOWERING PLANT
Tropical biology Page 81. Fig 7.1 or fig 5.1 page 15 introduction to biology
ROOTS
A root develops from the radical of the embryo during germination.
KINDS OF ROOTS
There are three kinds of roots namely;
1) Primary root-this is the first root to grow out of a seed as an extension of the radical
2) Secondary roots-these are roots that grow laterally from the primary root.
3) Adventitious roots-these are roots that grow from stems or leaves and nodes as branches
from either primary or secondary roots.
FUNCTIONNS OF ROOTS
Roots have three main functions i.e.
1) They hold the plant firmly in the soil
2) They absorb water and mineral salts for the plant from the soil.
3) They conduct the absorbed water and mineral salts up to the stem.
Others are
4) In some plants roots are modified into root tubers which store food e.g. cassava, carrot sweet
potato.
5) Some roots are modified for breathing e.g. white mangrove.
TYPES OF ROOTS SYSTEMS
There are two types of root system. These are
1) Tap root system.
2) Fibrous root system.
TAP ROOT SYSTEM
This consists of the main root growing straight downwards and often thickened.
The main root called tap root grows from the radical which persists and continues to grow. The tap
root then grows and gives rise to side roots called lateral roots. Tap root system is a characteristic of
cotyledonous plants.
Diagram showing a tap root system.
Page 21 Fig 5.12 (a) introduction to biology
FIBROUS ROOT SYSTEM
This is a root system without a main root and all roots arise from the same point at the base of the
stem. The roots here are almost of the same size. This type of root system is a characteristic of
monocotyledonous plants.
DIAGRAM OF A FIBROUS ROOT SYSTEM OF A PLANT.
Tropical Biology. Page 82 fig 7.3 or Page 21 fig 5.12 (b) introduction to biology
ROOTS CLASSIFICATION
True roots
1. Tap root system
a. Storage roots
b. Breathing roots
Adventitious roots modifications
1. Fibrous root system
2. Breathing roots
3. Storage roots
4. Stilt root
5. Buttress roots
6. Clasping roots
7. Sucking roots
8. Epiphytic roots
9. Prop roots
MODIFICATION OF THE TAP ROOTS SYSTEM.
Storage roots
These are thick fleshy and succulent roots. They contain stored food like sugars and starch. These roots
are classified as root tubers. Examples are carrots, cassava root tubers.
DIAGRAM OF A CARROT
Page 132 fig 11.17 tropical biology
Breathing roots
These roots are found on some plants growing in muddy areas e.g. white mangrove and black mangrove.
Breathing roots grow up through the mud to the air. The root parts above the mud are spongy and absorb
air from the atmosphere.
Diagram of breathing roots of white mangrove
Page 83 fig 7.4 tropical biology
MODIFICATIONS OF THE ADVENTITIOUS ROOTS.
a) Stilt root.
These roots develop from the main stem of certain plants such as red mangrove which grow in muddy
areas. Stilt roots provide additional support to the plant.
Diagram of stilt roots of red mangrove
Page 83 tropical biology. Fig 7.4
b) Buttress roots.
These are large thick toots growing from the base of certain stems e.g. mvule, silk cotton. They
provide extra support to the plant by anchoring it firmly in the soil.
Diagram of buttress roots of Buttress roots
Page 83 tropical biology. Fig 7.4
c) Clasping roots
These are roots growing from the nodes of climbing stems of some plants such as figs and orchids.
The roots enable the plant to cling onto another plant for support.
Diagram of clasping roots of epiphytic fig
Page 83 tropical biology. Fig 7.4
d) Prop roots
These develop from the nodes of a stem close to the soil surface. The y provides extra support to the
plant. They are found growing in plants such as maize, sorghum, sugar cane etc.
Diagram of prop roots of maize
Page 83 tropical biology. Fig 7.4
e) Epiphytic roots
Epiphytes are special roots which hang freely in the atmosphere. They absorb moisture from the
atmosphere.
An epiphyte is a plant that grows and gains support from other plants.
f) Sucking roots
These are roots that grow on parasitic plants e.g. dodder plant. They grow from a stem and then
penetrate the host plant. The roots then absorb water, mineral salts and food substance from the host
plant