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close this bookBetter Farming Series 02 - The Plant: the Stem; the Buds; the Leaves (FAO - INADES, 1976, 30 p.)
close this folderThe leaves
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Open this folder and view contentsHow a leaf is made
View the documentThe shape of leaves
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Where are the leaves found?

· Leaves grow from leaf buds.
· Leaves are found on stems and side shoots or branches.
· They are joined to the branches by the leaf- stalk.


Pick up some leaves of a mango tree or coffee tree. Let us look at them.

· Leaves are usually of a green colour, more or less dark.
· They are joined to the stem by a stalk called the leaf- stalk.
· The leaf-stalk is continued into the leaf by the midrib.
· Other smaller veins branch out from the midrib. These are the primary and secondary veins.
· The whole flat part of the leaf is called the leaf blade or lamina.

A leaf

The leaf-stalk

Some plants have a short leaf- stalk.
For example, coffee, orange, hibiscus, guava.

Some plants have a long leaf- stalk.
For example, papaw or papaya, sweet potato

The leaf-stalk

Some plants do not have a leaf- stalk.
The leaves of maize, millet or rice surround the stem.
There is no leaf- stalk.

The veins

In the middle of the leaf there is the midrib.
On each side of the midrib other veins branch off.
These are the primary veins.
They are smaller. These primary veins divide into many still smaller veins.

Perhaps you have seen a leaf that has been eaten by insects.
The leaf tissue has gone and only the veins are left. It is like a spider's web.

What are the veins for?

They carry the sap.
The sap passes along the stem vessels.
Then it enters the vein vessels.

Cut a palm frond and you will see the sap flow. The vessels of the palm frond carry the sap.

In a man's body, the vessels carry the blood.
In a plant, the vessels carry the sap.

Sap is the blood of plants.

The shape of leaves

The leaves of yam are not like those of cassava.
You can recognize a plant by looking at the leaves.

Leaves are simple or compound.

· Simple leaf

The simple leaf can be entire or lobed.

Entire simple leaf
Examples: yam , millet, okra., hibiscus, maize, cocoa, teak, coffee

Lobed simple leaf
Examples: cassava, cotton

· Compound leaf

Look carefully at the drawing of a groundnut leaf. What it shows is not four groundnut leaves. It is a single leaf.
But this leaf is made up of a midrib bearing four little leaves.
These little leaves are called leaflets.
The midrib of a compound leaf is not a stem.
So there is never a bud between the midrib and the leaflets.

A groundnut leaf


To live, a man feeds and breathes.
To live, a plant also feeds and breathes.


· The plant takes up food from the soil through its roots. It takes water and mineral salts from the soil (see Booklet No. 1, page 17). But it has to change the water and mineral salts.
A baby drinks only milk. Its hair grows and so do its arms and legs.
It becomes strong and heavy.
The baby has changed the milk in its stomach into hair, fat, muscles, etc.

· The leaf changes the water and mineral salts taken from the soil by the roots. Water and mineral salts make up the raw sap (see Booklet No. 1, page 19, and Booklet No. 2, page 21 ).
The leaf changes the raw sap into elaborated sap.
The leaf sends the elaborated sap into the buds, flowers, fruits, stem and roots.

The elaborated sap feeds the whole plant.

· The leaf changes the raw sap into elaborated sap.

The elaborated sap FEEDS:

The elaborated sap feeds

How the leaf changes raw sap into elaborated sap

· The leaf feeds the plant.
It receives the raw sap; it changes the raw sap into elaborated sap.
This change is called plant material synthesis.

What is plant material synthesis?

· Heaps of sand, wood and bricks are not a house.
To build a house you have to put them together.
You join them with cement.
The cement changes the wood, sand and bricks into a house.

· Water and mineral salts cannot feed the plant.
They have to be put together, they have to be joined.
How are water and mineral salts joined together?

· The leaves live in the air.
The air contains carbon dioxide gas.
The carbon dioxide gas is made of oxygen and carbon.
The leaf keeps the carbon and gives off oxygen.

· The carbon joins the mineral sale and the water.
The mineral salts and water are changed into elaborated sap.
The elaborated sap can then feed the plant.
The carbon changes the raw sap into elaborated sap.
This is plant material synthesis.
To join sand, wood and bricks with cement requires work.
You can't have a house without men's work, men's energy.
To join water and mineral salts with carbon also requires work and energy.

· Light gives the leaf this energy.

Light enables the leaf to change raw sap into elaborated sap.
At night there is no light, and the raw sap is not changed.

Light enables the leaf to change raw sap into elaborated sap

Organic matter in the plant

The plant gets water and mineral salts from the soil.
This is inorganic matter.
This inorganic matter is changed by light and carbon and becomes elaborated sap.
The elaborated sap feeds the plant.
Just as blood enables a man to make his muscles, hair, bones, so elaborated sap enables a plant to make leaves, wood, fruits. The leaves, the wood, the fruits are organic matter.

Inorganic matter has become organic matter.

The plant breathes.

To live, a man feeds and breathes.
To live, a plant also feeds and breathes.
A plant breathes through its leaves.

The plant transpires.

When it is hot, a man sweats, he transpires.
A plant also transpires.
The water in the sap evaporates, the leaf gets dry.
The plant is thirsty.