Twenty-three titles have been published in this series, designed as handbooks for intermediate level agricultural education and training. They may be purchased as a set or as individual documents.
1. The way to work. The living plant
2. The plant – the root
3. The plant – the stem
4. The plant – the leaf
5. The plant – the flower
6. The soil – man and the soil
7. The soil – how the soil is made up
8. The soil – the living soil – working the soil
9. The soil – working the soil (continued)
10. The soil – conserving the soil – improving the soil
11. Animal husbandry – introduction
12. Animal husbandry – feeding animals
13. Animal husbandry – looking after animals – how cattle reproduce
14. Animal husbandry – what cattle produce
15. Keeping chickens
16. Food crops
17. Market gardening
18. The oil palm
20. Upland rice
21. Wet paddy or swamp rice
Published by arrangement with the Institut africain pour le développement économique et social
FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONS
© French edition, lnstitut africain pour
le développement économique et social (INADES) 1967
© English edition, FAO 1970
This manual is a translation and adaptation of “La plante- la feuille,” published by Agri-Service-Afrique of the Institut africain pour le développement économique et social (INADES), and forms part of a series of 23 booklets. Grateful acknowledgement is made to the publishers for making available this text, which it is hoped will find widespread use at the intermediate level of agricultural education and training in English-speaking countries.
It should be noted that the original texts were prepared for an African environment and this is naturally reflected in the English version. However, it is expected that many of the manuals of the series — a list of which will be found on the inside front cover — will also be of value for training in many other parts of the world. Adaptations can be made to the text where necessary owing to different climatic and ecological conditions.
Applications for permission to issue this manual in other languages are welcomed. Such applications should be addressed to: Director, Publications Division, Food and Agriculture Organization of the United Nations, Via delle Terme di Caracalla, 00100 Rome, Italy.
The cover illustrations were prepared by Asun Balzola.
• What does a leaf consist of?
How are the veins arranged?
What are the veins for?
Arrangement of leaves
The shape of leaves
• The function of leaves
How the leaf transforms raw sap into elaborated sab
How the leaf breathes
• Plants need light
• Protecting the leaves
Insects and diseases
• Suggested question paper
Read pages 4 to 10.
• Look carefully at the leaves collected.
Then study each page and learn the new words.
• Look carefully at a leaf; you will easily see the veins and the lamina between them.
Read pages 11 to 16.
• As a help to memory, reread pages 4 to 10.
Look at how the leaves are attached to the stem of the plants mentioned as examples.
• Cut a leaf from each plant. What is the edge like?
Read pages 17 to 24.
• The leaves transform the raw sap into elaborated sap.
The leaves breathe.
• This week’s work is more difficult.
You will need to spend more time on it.
Do not forget to read the previous booklets when there is a reference to them.
Read pages 25 to 29.
This will not take very long.
• Reread the whole booklet, especially the work for the third week.
• Answer the question paper.
Collect some leaves of yam, cassava, maize or millet, groundnuts or beans.
Look at them.
1. Leaves are mostly of a green colour, more or less dark.
2. They are attached to the stem by the leafstalk, the petiole.
3. The petiole is continued into the leaf by the midrib.
4. Other smaller veins branch out from the midrib. These are primary and secondary veins.
5. The space between the veins of the leaf blade is flat. This area is the lamina.
6. The petiole.
Some plants have a short petiole. For example, coffee, orange, hibiscus, guava.
Some plants have a long petiole. For example, papaya, sweet potato.
Some plants do not have a petiole. The leaves of maize, millet or rice surround the stem. They form a sheath. The sheath takes the place of the petiole.
7. The veins.
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 leaves that have been eaten by insects.
The leaf tissue has gone and only the veins are left.
it is like a spider’s web.
Let us look at a leaf of maize or millet, of cassava or cotton.
8. All leaves have a midrib.
But primary veins do not branch off from the midrib in all leaves.
On a leaf of maize or millet the veins never join. They follow the same direction. They are parallel.
9. The leaf of maize or millet has no petiole. The sap goes directly from the stem into the leaves.
Not all leaves have parallel veins or a similar vein system.
10. They carry the sap.
The sap passes along the stem vessels.
Then it enters the vein vessels.
Let us cut a palm frond. The sap flows. So the vessels of the palm frond carry the sap.
11. In a man’s body, the vessels carry the blood.
In a plant, the vessels carry the sap.
Sap is the blood of plants.
12. Let us take an example.
Near big cities the roads are wide.
Near the stem the midrib is thick.
On each side of the road smaller tracks branch off. There is less traffic.
On each side of the midrib smaller veins branch off. There is less sap.
Far from the cities, in the fields, the tracks are very small. There are few people.
Far from the midrib, at the edge of the leaf, the veins become smaller and smaller. They carry little sap.
How are the leaves joined to the stem?
13. Alternate leaves, for example, yam leaves.
14. Opposite leaves, for example, teak and coffee.
15. Verticillate leaves, for example, leaves of allamanda.
16. Alternate leaves
Only one leaf grows from the same place on the stem.
Another leaf grows above, from the other side of the stem. On the stem you find one leaf on one side, then a leaf on the other side, but you never find two leaves growing from the same place.
We say, the leaves are alternate.
Yam, pimento, sugarcane, sweet potato, millet, maize, hibiscus, okra, all have alternate leaves.
17. Opposite leaves.
Two leaves grow at the same height, one on each side of the stem.
We say, the leaves are opposite.
Teak and coffee have opposite leaves.
18. Verticillate leaves.
3, 4 or 5 leaves grow at the same height of the stem.
We say, the leaves are verticillate.
Allamanda leaves are verticillate.
The leaves of yam are not the same as those of cassava. You can recognize a plant by looking at the leaves.
Leaves are simple or compound.
19. Simple leaf
The simple leaf can be entire or lobed.
20. Compound leaf
Look carefully at the drawing of the 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.
Many plants and trees have compound leaves.
The bean leaf has 3 leaflets.
The cassia leaf has many leaflets.
21. The edge of a leaf is smooth or dentate.
To Sum up
We have learned to look at leaves.
We recognize them by:
• their size – large or small
• the petiole – short, long, or not present
• the number and form of the veins
• the position of the leaves on the stem – alternate, opposite, verticillate
• the form – simple or compound
• the edge – smooth or dentate.
22. To live, a man feeds and breathes.
To live, a plant feeds and breathes.
The leaf helps to feed the plant
23. The plant takes up food from the soil through its roots – water and mineral salts (see Booklet No. 2, paragraph 31). But it then has to transform them.
A baby drinks only milk. Its hair grows, and so do its arms and legs. It becomes strong and heavy. The baby has transformed the milk in its stomach. The milk has been transformed into hair, fat, muscles, etc.
24. The leaf transforms the water and mineral salts taken from the soil by the roots. Water and mineral salts make up the raw sap (see Booklet No. 2, paragraph 38 and Booklet No. 3, paragraph 27).
The leaf transforms the raw sap into elaborated sap.
25. The leaf sends the elaborated sap into the buds, flowers, fruits, stem and roots.
The elaborated sap feeds the whole plant.
26. The leaf transforms the raw sap into elaborated sap.
27. The leaf feeds the plant. It receives the raw sap; it transforms the raw sap into elaborated sap.
This transformation is called plant material synthesis.
28. What is plant material synthesis?
The leaf contains the raw sap. The leaf takes up carbon from the air.
29. The carbon transforms the raw sap into elaborated sap. That is plant material synthesis.
30. Where does the carbon come from?
The air contains carbon dioxide gas. The carbon dioxide gas is made of oxygen and carbon.
The leaf retains the carbon and gives off the oxygen.
31. What does the carbon do?
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.
This cement transforms the wood, sand and bricks into a house.
Water and mineral salts cannot feed a plant.
They have to be put together, to be combined.
The carbon combines the mineral salts and the water.
The mineral salts and water are transformed into elaborated sap.
The elaborated sap can then feed the plant.
32. To join the sand, wood and bricks with cement, work is necessary.
You never get a house without men’s work, men’s energy.
To join water and mineral salts with carbon also needs work and energy.
33. Light gives the leaf this energy.
The work done in the leaf by light is called photosynthesis.
There is no photosynthesis at night.
The energy is given to the leaf by light.
It is also given by breathing (or respiration).
34. To live, man breathes – he takes in air through his nose and mouth.
To live, the plant breathes – it takes in air through its leaves.
35. The stomata are the nose and mouth of leaves.
On the leaf surface there are many little holes.
These little holes are the mouths of the leaf – the stomata.
You need a microscope or a lens to see them.
When a man’s nose and mouth are closed, no air goes in; the man no longer breathes.
When the stomata of a leaf are closed, no air goes in; the plant no longer breathes, the leaves become soft and dry – they wilt.
The plant dies.
36. The stomata may close when the plant lacks water.
When there is not enough rain, the roots do not find water, the leaves wilt, the plant breathes badly.
If there is a great lack of water, the plant gives a very low yield.
The plant has not breathed well. It does not produce many fruits or seeds. It may die.
37. You understand now why you have to give the plant water.
When there is enough water, the plant breathes well, and it produces plenty of seeds or fruits.
38. Young plants do not have much root.
They cannot seek out water that lies very deep. They wilt quickly if they are left in the sun.
Seedlings must be protected by covering them, for instance with branches.
Seedlings must be well watered.
39. Leaves breathe. The leaves help to feed the plant.
40. If the leaves are plentiful and big – the yield will be good.
If the leaves are few and small – the yield will be less good.
41. The plants sown at the best density (see Booklet No. 2, paragraph 35) will have the best leaves.
The roots will find enough food and the leaves will transform this food properly – the yield will be good.
42. When plants of cotton or maize are too close together, the surplus plants are removed.
43. On rich soil rice seedlings are green.
On poor soil rice seedlings become yellow.
By looking at the plants growing in a soil you can tell if the soil is good or bad.
By looking at the leaves you can tell the state nutrition.
If you enrich the soil with fertilizers, the leaves will become green and more seeds will be produced.
44. For an oil palm to have big fruits, its leaves must metabolize a lot of mineral salts and water.
To make its fruits the palm must obtain plenty of mineral salts from the soil.
If the soil does not have enough potassium, we give it a potassic fertilizer.
The palm can then produce many large fruits.
45. To get a lot of cotton you must give the cotton plants plenty of mineral salts.
The cotton leaves metabolize water and mineral salts.
Fertilizers are mineral salts. So we give fertilizers to cotton.
46. If a plant is not in the light it does not grow well.
Light does not pass through the leaves of a dense mango tree, and almost nothing grows under it.
There are very few weeds.
To grow, weeds need light.
47. To make salad plants go white, you tie the leaves together with string.
The light does not get through.
The leaves grow less.
They remain white.
48. Leaves can become ill.
Then the plant is badly fed.
Crops must be protected against disease.
Air does not move easily among plants that are too close together.
If the air does not circulate well, the plants often become ill.
49. The air will move better:
• if we pull out the weeds
• if we prune trees such as coffee, cocoa
• if we grow crops on fairly high ridges, as we do with groundnuts, cotton, lettuces.
• if we make stems climb on sticks or branches, for instance cowpea, tomato, yam.
With good air circulation, diseases develop less.
Well-ventilated plants are more able to resist disease.
50. Some insects eat leaves and buds.
Young leaves are eaten first because they are softer. When the insects are born, the plants should already be strong.
The leaves, being harder, will be less attacked.
Plants sown at the right time will be strong when the insects appear.
51. Insects and diseases can be destroyed.
After the harvest of cotton or groundnuts, the plants are often left on the soil.
Then the insects and diseases remain there until the next year.
The next harvest will not be a good one.
You should pull up the plants after the harvest.
Let them dry and then burn them.
The field is cleaned, the insects and diseases are destroyed by the fire.
Some seeds give strong plants.
These vigorous plants resist diseases and insects better.
You should sow seeds which resist diseases and insects.
52. To kill insects or to prevent diseases we can use pesticides.
These pesticides are poisons.
You cover the leaves with them and the insects are killed.
Often you need a pump so that the pesticide fully covers the whole plant.
53. These pesticides can be dangerous to men and animals. You have to be very careful.
54. These pesticides kill certain insects, but not others.
55. You must use exactly the quantity written on the container, no more and no less.
56. Leaves and plants must also be protected against animals, such as goats, cows, agoutis, monkeys.
Fields must be enclosed and a watch kept for cows and goats.
The lamina is the flat part of the leaf
Yes or No
The maize leaf has a petiole
Yes or No
The bean leaf has three petioles
Yes or No
The raw sap feeds the plant
Yes or No
When there is not enough water, the plant breathes well
Yes or No
The petiole is continued into the leaf by the __________
The cassia leaf has several __________
The __________ joins the mineral salts and the water.
The nose and mouth of leaves are the __________
Pesticides are __________ for insects.
ANSWER THE FOLLOWING QUESTIONS
What is the petiole?
What are veins for?
What does carbon do in the leaf?
Why do young plants wilt quickly?
What should the farmer do to protect his crops against disease?
What are leaves for?
What is elaborated sap?
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Better Farming Series, no.4. This handbook is designed for intermediate level agricultural education and training.This manual is a translation and adaptation of "La plante: la feuille," published by the Agri-ServiceAfrique of the lnstitut africain pour le developpement economique et social (INADES), and forms part of a series of booklets. Grateful acknowledgement is made to the publishers for making this text available for English-language agricultural education and training.The manual describes leaf shape, function and how to protect leaves from diseases and pests. It is illustrated with examples.