Better Farming Series    2

The Plant

— The Root

Published by arrangement with the Institut africain pour le développement économique et social

FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONS

Rome 1970

Contents

1. Preface

2. Outline Of Course

3. Are all roots alike? Yes and no

4. Different root systems

1. Fibrous root

2. Creeping root

3. Tap-root

4. Tuberous root

5. Adventitious root

5. How a root system is built up

6. What does a radicle consist of?

7. There are root-hairs on the rootlet

8. The function of roots

1. Roots hold the plant in the soil

2. Roots feed the plant

9. Suggested question paper

PREFACE

This manual is a translation and adaptation of “La plante: la racine,” published by the 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.

OUTLINE OF COURSE

• Are all roots alike? Yes and no

• Different root systems

Fibrous root

Creeping root

Tap-root

Tuberous root

Adventitious root

• How a root system is built up

• What does a radicle consist of?

• There are root-hairs on the rootlet

• The function of roots

Roots hold the plant in the soil

Roots feed the plant

• Suggested question paper

PLAN OF WORK

Roots and stems (Booklet No. 3) will be your work for two months.

The first course, on the root, is fairly long. The second, on the stem, will be shorter.

So you will study the root for six weeks and the stem for two or three weeks.

FIRST WEEK

THE WAY TO WORK AND THE LIVING PLANT

• Reread all of Booklet No. l with great attention.

• Begin the experiments on germination and lifting a root.

Look after your seeds.

Water them every morning.

SECOND AND THIRD WEEKS

THE FIVE ROOT SYSTEMS

• Read pages 4 to 17 in this booklet.

• To help your memory, reread pages 13 to 26 of Booklet No. 1.

Read quickly this booklet from page 4 to page 17. You must know the right name for each root system and understand fully each drawing.

FOURTH WEEK

ANATOMY OF ROOT SYSTEM

• Read pages 18 to 23.

• How is a root system built up?

• What does a radicle consist of?

• There are root-hairs on the rootlet.

• To help your memory reread pages 4 to 17.

Do over again the experiments on seed germination and lifting a root.

• Study this new lesson carefully. It is a little more difficult.

FIFTH WEEK

THE FUNCTION OF ROOTS

Read pages 24 to 28.

• Roots hold the plant fast in the soil.

• Roots feed the plant.

To help your memory, first reread pages 20 to 23. There are not many pages in the new lesson, but you must understand them very well.

If you do not understand properly, get the pages explained to you.

SIXTH WEEK

ANSWER QUESTION PAPER

• Reread quickly all of Booklet No. 2.

• Try to answer the question paper without looking at the text.

• Look in the text to see if your answers are right.

ARE ALL ROOTS ALIKE?

YES

1. Roots are alike — they are under the earth. Roots are the underground part of the plant.

No

2. Maize, rice or millet have many fine roots. Cassava has few and thick roots.

Cotton has some thick roots and some little ones. The smallest are called rootlets.

DIFFERENT ROOT SYSTEMS

The roots of a plant taken altogether are called the root system of a plant.

3. The root systems of a maize plant, a millet plant and a wheat plant are alike.

• The root systems of a mango tree, an orange tree and a lemon tree are alike.

• The root systems of maize, millet and wheat are not like those of the mango tree, the orange tree and the lemon tree.

• Different plants have different root systems.

There are five groups of root systems: fibrous, creeping, tap-root, tuberous and adventitious.

4. All plants have a part that lives in the earth - the root system.

5. All plants have a part that lives in the air - the aerial system.

6. The collar joins the root system to the aerial system. It connects them.

FIBROUS ROOT

7. Some plants have small, thin roots, all of the same length.

• These roots form a tuft, as for instance the roots of onion, rice, millet, wheat.

• A plant that has many small roots, of the same length, the same thickness, the same shape, has a fibrous root system.

8. Maize, millet, rice and sorghum are grain-producing. grass-like plants.

They have a fibrous root system.

• They have leaves and produce grain.

The leaves are used as food for animals.

The grain is used as food for animals and also for people.

9. There are other grasses. For instance elephant grass, Guinea grass, citronella grass.

Their stems and leaves, green or dried, can be fed to animals.

Grass dried in the sun is called hay.

• When the plant is dead, its roots remain in the earth.

They rot and improve the soil.

CREEPING ROOT

10. Some plants have roots that are shallow and long.

• These roots are thick. Smaller roots grow on the thick ones.

• A plant that has shallow, very long roots has a creeping root system.

11. The roots in a creeping root system do not go deep into the soil.

Trees can be torn up by strong winds.

In a sandy soil trees are easily torn up.

12. Such roots go a long way from the base of the tree.

They cover a large area.

They have to find in a small depth of earth the food necessary for the life of the plant.

The plant will grow well if it finds plenty of food.

The plant will grow badly if it does not find enough food.

Food has to be given to the soil in the form of fertilizers.

These fertilizers are spread on top of the soil.

13. You must not put other plants near the base of a plant with a creeping root system.

If you do, all of them will grow badly.

They cannot develop.

They will not have enough food.

TAP-ROOT

14. Some plants have only one root, a very thick one.

• This root goes down deep and straight into the soil. It is called a tap-root.

• Smaller roots grow on this thick root; they are called rootlets. Rootlets gather food for the tap-root.

• Cotton, coffee, cocoa, okra, carrots, papayas all have a tap-root system.

15. Tap-roots grow deep into the soil.

When the soil is too hard, they cannot grow downward.

The root stays on the surface.

It will be poorly fed and will not grow well.

A plant with a tap-root system must not be planted in a soil that is too hard.

A plant with a tap-root system that is put in good soil can send its root deep down into the soil.

It will be well fed.

16. The rootlets of tap-roots do not spread very far from the tap-root.

So two plants can be sown or planted very close together.

They will both be well fed.

They go far down into the soil for their food.

17. Plants with a tap-root system can be placed alongside plants with a creeping root system.

The plant with the creeping root system finds its food on the surface.

The plant with the tap-root system finds its food in deeper soil.

However you can only do this with certain plants and only on very rich soil.

Before planting, always ask for advice from the agricultural assistant.

TUBEROUS ROOT

18. Some plants have very thick roots.

• These roots store up food.

• Cassava has a tuberous root system.

19. These roots are thick because they have taken up a lot of food from the soil.

The food is stored up in order to feed the whole plant.

The plant is said to have built up reserves.

20. In good soil the plant will have plenty of reserves, so it will have big roots.

In poor soil the plant will have few reserves, so it will have small roots.

21. The most important foods in reserve are different forms of starch. Starch is used to feed both men and animals.

ADVENTITIOUS ROOT

22. In some plants roots start from the stem above the soil — that is, above the collar — and afterward go down into the earth.

• There they produce smaller roots.

• Mangrove, bamboo, maize and rice all have an adventitious root system.

23. Adventitious roots grow above the collar.

• Soil put around the collar helps adventitious roots to grow.

Putting earth round the collar is called earthing up.

The new adventitious roots help the plant to support itself more firmly in the soil.

They give the plant greater support and it is better fed.

24. Some plants do not always have a single root system.

Cassava, for instance, has at the same time both tuberous roots and other roots which are not tuberous.

HOW A ROOT SYSTEM IS BUILT UP

25. We have lifted some roots.Let us look at them.

• What do we see? A number of big roots start from the collar. These roots divide up into smaller roots and into rootlets.

• The smallest roots are called rootlets.

WHAT DOES A RADICLE CONSIST OF?

26. There are parts of the radicle which perhaps you cannot see, because they are too small or because they have remained in the ground.

• To see them better, make another seed germinate. Put a bean seed in the earth. After three days lift it carefully. The roct should be about as long as a match.

27. What do you see?

At the tip of the rootlet there is the root- cap. It is like a hat.

• A hat protects the head.

The root-cap protects the radicle.

• The root-cap is very small. It is difficult to see.

• It is hard. Its purpose is to enable the radicle to penetrate the soil.

28. To see better, you need a lens or a microscope. These instruments enable you to see the rootlets enlarged. Perhaps your agricultural assistant or your teacher can lend you one.

• The drawing on the facing page is much larger than the real root-cap, which is so small that you cannot see it without a magnifying instrument.

A human eye cannot see very small things. We have to use magnifying instruments. They help us to see the smallest things. For example, when you look at a tree from a distance, you see a green mass. But if you come nearer, you see separately a stem, branches, leaves.

Many things can be understood if you can look at them very closely.

Magnifying instruments help us to see things very closely and very much bigger.

THERE ARE ROOT-HAIRS ON THE ROOTLET

29. There are many of these hairs, but they are thin, short and fragile.

Perhaps you cannot see them, but they have a very important function. These hairs are like those on your head but they are very short, and thin, and there are very many of them.

These hairs are called absorptive hairs because they take from the soil the food which the plant needs in order to live and grow. They are like little mouths that take in food for the plant.

The hairs absorb plant food.

Note that

30. Between the root-cap and the root-hairs there is a white part without hairs called the smooth region.

It is from this region that the root grows.

31. In the soil, mixed with it, are mineral salts.

These mineral salts are the plant’s food.

The absorptive hairs take up this food from the soil.

32. Above the root-hairs there is a dark, hard part.

This is the oldest part of the root.

It does not take up food.

It does not absorb it.

THE FUNCTION OF ROOTS

ROOTS HOLD THE PLANT IN THE SOIL

33. Rain, a stream or the sea sometimes pulls up roots.

Then the plant or tree falls and dies.

In order to live the plant must be held fast in the soil by its roots.

Note that

34. It is important for plants to be held fast in the soil because a plant will grow well if it has strong roots. To become vigorous a plant needs to spread out its roots.

35. When you sow maize or millet seeds too closely together, each plant does not have enough room in the soil to make good roots, and so the stems and ears do not grow well.

The harvest will be poor.

When you sow maize or millet seeds too far apart from each other, the ears grow well but there are too few of them.

You should sow the seed so as to have the largest number of vigorous plants over the smallest area.

You have to find out the correct number of seeds, you should sow in a plot; that is, the best density.

ROOTS FEED THE PLANT

36. If a plant has a well-developed root system, it is well fed and the harvest is better.

37. If a plant can find more food in the soil, it is well fed and the harvest is better.

A plant grows very well, gives a better harvest and produces more

if the roots are well developed

if the soil is rich.

Note that

The food a plant finds in the soil is made up of mineral salts.

What are mineral salts?

38. When you burn a tree or some leaves, what remains are ashes.

These ashes are mineral salts.

Mineral salts dissolve in the water in the soil.

The mineral salts and the water are absorbed by the root-hairs.

They become the raw sap of the plant.

39. When there is a plentiful supply of mineral salts in the soil, the soil is rich. The plant grows well.

• When mineral salts are in short supply in the soil, the soil is poor. The plant grows badly.

The soil can be given mineral salts - in the form of fertilizers and manure.

SUGGESTED QUESTION PAPER

UNDERLINE THE RIGHT ANSWER

Are the root systems of millet and cassava alike

Yes or No

A fibrous root system forms a tuft of small roots

Yes or No

Plants with a creeping root system have very deep roots

Yes or No

A tap-root is a small, shallow root

Yes or No

The root-hairs are for feeding the plant

Yes or No

The plant takes water and mineral salts from the soil

Yes or No

FILL IN THE MISSING WORDS

The__________connects the aerial system and the root system.

Millet has a__________root system.

In a creeping root system the roots are__________and very__________

The smallest roots are called__________

There are many__________on the rootlets. They are very fine and short.

In order to live a plant must be__________to the soil by its roots.

ANSWER THE FOLLOWING QUESTIONS

What is a tap-root like?

Give examples of tap-roots growing near your home.

What is a cassava root like? Why?

Do you know any plants with an adventitious root system? Name them.

What are the roots of these plants like?

What is meant by earthing up?

You have made a seed germinate and lifted it after three days.

What do you see?

What is the function of root-hairs?

Why must we sometimes put fertilizers or manure on the soil?