|Better Farming Series 02 - The Plant: the Stem; the Buds; the Leaves (FAO - INADES, 1976, 30 p.)|
· The root is the part of the
plant that lives in the soil.
· The stem is the part of the plant that lives in the air, above the soil.
· The crown, or collar, joins the root and the stem.
· The stem bears leaves, flowers, fruits.
· Leaves, flowers, fruits, all grow on the stem.
Plant and its roots
· The stem can be trailing, for example, that of a groundnut plant, or of a marrow, cucumber or melon.
Let us look at a groundnut plant. What do we see?
A groundnut plant
A groundnut plant has several stems.
They are easy to cut or crush between the fingers.
They are not hard.
The stems lie on the ground or are upright.
· The stem can be climbing, for example, that of the yam, bean, pea, and all the creepers.
Let us look at a yam plant.
What do we see?
· A yam plant may have several stems.
The stems lie on the soil.
If you push a stick into the ground beside a yam, the stems can
be held upright, because they hold on to the stick.
The stem winds round the stick and climbs.
· The stems bear rather large green leaves and clusters of little flowers.
· The stem can be upright, for example, that of millet, maize, sorghum, cassava
Cotton, kapok tree or baobab.
Maize has only one seam.
The stem is upright.
It is harder than the stem of groundnuts or yams.
Trees: The stem is upright, very tall, very thick, hard.
It is called the trunk.
The trunk of a tree is its stem.
· The stem can be underground, for example that of garlic or onion.
Let us look at an onion.
What do we see?
· A very thick stem, in the
ground; this is the onion.
· Long leaves come out of the stem.
· Roots grow in a ring at the base of the stem, at the base of the onion.
· These stems hold a lot of food.
HERBACEOUS STEMS AND WOODY STEMS
· The stems of groundnuts, yams, maize, millet, tomato and okra are green and pliable.
They can be bent without breaking.
They are like grasses.
They are called herbaceous stems.
· The stems of cotton, kapok trees, coffee, cocoa, of all trees, are hard.
They break if you try to bend them.
You have to strike hard to cut them with a machete.
They are called woody stems.
ANNUAL STEMS AND PERENNIAL STEMS
· The stems of groundnuts, maize, millet, tomato and okra last for only one year. They are called annual stems.
· The stems of the kapok tree, coffee, cocoa, the underground stem of yams, last for many years. They are called perennial stems.
· It supports leaves and
· It circulates sap.
THE CIRCULATION OF SAP
Cut through the stem of a coffee tree or of a lemon tree. What do we see?
· First of all, on the outside of the stem, there is the bark.
This is the skin of the tree.
Skin protects a man or an animal.
The bark protects a tree stem.
If a goat eats the bark, or you cut it with a hoe, the plant is no longer protected. It is injured.
Many diseases can get in through this injury.
You must not injure the bark.
· Under the bark is the wood.
When the tree is old, the wood is thick, the stem is
Wood makes the stem hard.
Cut stern of a lemon tree
In the wood you can see many little holes.
These are little tubes or vessels.
In a man's body the blood is carried by blood vessels.
In a plant, vessels carry the sap.
· In the centre of the stem is the pith.
If you cut a cotton stem you can see the pith very easily.
It is less hard than the wood.
Often it is not the same colour.