English for Academic Purposes for Students of

Agricultural Studies

Dr Eirene C. Katsarou (PhD, MA, MA Ed, MDE)

School of Agricultural and Forestry Sciences, DUTHEmail: ekatsai@otenet.gr

Website: http://www.ekatsarou.edu.gr

Unit 11 Asexual Reproduction

When a part of the plant other than its seed is used in developing a new plant, it is called vegetative reproduction. Some plants, such as potato and banana, produce few seeds while others, such as peach and pecan, seldom come true from seed. Vegetative reproduction is practiced generally in order to preserve good varieties.

Apart from grafting and budding, which are the principal ways by which vegetative parts of plants can be used to produce new plants, there are other methods by which asexual reproduction can be completed.

Natural layers: Many plants develop horizontal stems called stolons, which develop roots and new shoots at nodes, though roots frequently develop at other points too, along the internode. After such layers have taken root and have made additional growth above ground, they are often indistinguishable from the mother plant.

Artificial layers: The grape and many other plants do not ordinarily produce natural layers. Yet, if vines or stems are bent to the ground and covered with moist soil, they will take root and grow. The rooted part may then be separated from the mother vine and planted out in a new location to grow.

Modified stems: Some plants produce underground stems, which, when separated from the plant, will serve to reproduce it. The rhizome of the Johnsongrass and the tuber of the Irish potato are examples of such modified stems. The ‘eyes’ of the potato are actually modified buds, which under favourable conditions, develop a new plant.

Fleshy roots: The sweet potato, as example of a fleshly root, has no eyes or buds like the Irish potato. It, however, does develop special buds which grow into young vines, called slips.

Cuttings: A cutting is a piece of stem, leaf or root, which will form a new plant if cut off from the parent and planted under favourable conditions. It develops roots from the base and the buds are already present grow. Usually such cuttings are planted out in sand. Plants that do not have a cambium layer seldom grow well from cuttings. Of the plants that have a cambium layer, some will grow readily and others will not.

Text 2: Maintaining Continuity…

Asexual reproduction differs from sexual reproduction in that it does not require 2 parents, and that special cells are not required. This also means that the special mechanisms necessary to bring together sex cells and permit fertilization, in order to support development of the fairly helpless stages, from zygote to independent organism, are not required.

Although we often think of plants when we consider asexual reproduction, it must be remembered that there are many animals which reproduce asexually. The simplest organisms (Amoeba, bacteria, etc) may rely on asexual reproduction alone; but many organisms are able to use both methods, according to the requirements of their life-cycle.

Asexual reproduction in plants is also called vegetative reproduction because it simply involves the growth of parts which eventually become detached to form new plants. Since the new parts are produced by ordinary cell division, they are direct copies of the original, with no input from another individual as in sexual reproduction. Consequently, asexual reproduction does not introduce variation, unlike sexual reproduction (flowers and their products: seeds). However, it follows that asexual reproduction may be seen as a means of maintaining continuity. It is also a fairly quick method of increasing numbers.

The same principle can also be used by Man in order to grow more plants, perhaps starting from only one plant, a process called artificial propagation. This is especially useful if you want to produce many copies of a plant which has some desirable characteristics, such as flowers of a different colour, or fruits with a particular taste or quality. One fairly easy way of doing this is to take cuttings of a plant, by removing part of a plant, which then eventually grows into a whole plant on its own.

Key to ExercisesReading Comprehension

Exercise 1:

1. F

2. F (vegetative reproduction)

3. T

4. F (the plant itself)

5. F (underground stems)

6. T

7. T

8. F (for good varieties)

9. T

Exercise 2:

1. natural layers

2. artificial layers

3. modified stems

4. fleshy roots

Key to ExercisesReading Comprehension

Exercise 3:

Pollination is the process whereby pollen grains are transferred from the male parts of the flower to the female parts. More specifically, the male sexual organ, or stamens, produces the pollen which contains two male gametes. Then, pollen is carried by wind or insect from the stamens to the stigma or the carpel. The next stage is fertilization.

2, 4,1,3

Key to ExercisesReading Comprehension

Exercise 4:

1. Vegetative reproduction is the process by which a part of the plant is used for the development of a new plant and it is practiced to preserve good varieties.

2.Vegetative reproduction can be achieved by the use of vegetative parts of plants.

3. An examples of a plant that uses artificial layers for its production is the vine. When their rooted part is separated from the mother vine it can be planted out and grow in a new location.

4. A cutting develops roots from the base and buds when planted out in sand.

Key to ExercisesVocabulary

Exercise 5:

1. node

2. slot

3. modified

4. readily

Exercise 6:

1. orchardist

2. asexual

3. peach

4. seeds

5. artificial

6. modified

7. cuttings

8. natural

9. applies

10. Nevertheless,

11. reproduction

12. require

Key to ExercisesVocabulary

Exercise 7:

1. f

2. b

3. a

4. e

5. d

6. g

7. c

Unit 12 Grafting and Budding

Instead of cutting off a piece of the plant and planting it in the soil to make it grow, we can insert it in the body of another plant and let it grow there. If the inserted piece is a part of a stem, it is called grafting.

Nearly all grafting work is done when the plant is dormant. The plant upon which the piece is grafted is called the stock, and the part that is transferred is called the scion. Plants must be closely related, otherwise it is not possible for one to live when grafted on the other. Usually they should belong to the same species, but sometimes even different genera may be grafted as, for example, the pear may be grafted upon the quince. When the transplanted graft lives and unites with the stock all the limbs, leaves and fruit developing from the graft remain true to the variety from which the graft was taken, in spite of the fact that the raw food material is furnished by the root of the plant in which the graft was planted. This makes it possible to put grafts from fine varieties on trees or vines that bear naturally poor fruit, and thus force them to bear good fruit instead of poor. The most important forms of grafting are tongue or whip grafting, cleft grafting, and bark grafting.

If the part cut off and inserted in the other plant is only a bud with some bark surrounding it, the operation is called budding. Budding accomplishes the same results as grafting. It is difficult to tell whether a tree has been grafted or budded after a few years. Budding is usually done during the plant’s active growing season. Again the two plants must be closely related and the cambium layer of the bud must be brought into connection with the cambium layer of the stock.

The three most important forms of budding are the shield bud (or T bud), the patch bud, and the chip bud. Nearly all fruit and ornamental trees are propagated by the shield bud, while the chip and patch buds are usually best for nut trees.

Key to ExercisesReading Comprehension

Exercise 1:

1. T

2. F (quality)

3. F (only grafting)

4. F (vegetative reproduction)

5. F (it uses the raw food material of the stock)

Key to ExercisesReading Comprehension

Exercise 2:

Grafting is a process through which we can force plants to bear good yield. This can be achieved by inserting a piece of plant in the body of another and helping it grow there. Grafting takes place when the plant is dormant. What is important is that grafted plants should belong to the same species. During the process, the roots of the plant provides the food material for the new plant while the fruit it bears is of the variety from which the graft was originally taken.

Key to ExercisesReading Comprehension

Exercise 3:

1. Grafting can be done when the plant is dormant while budding can be practiced when it is active.

2. In both grafting and budding plants should belong to the same species but it depends on whether the plant is active or dormant to practice each one of the two.

3. They help us to retain good varieties and enhance the quality of yield.

Key to ExercisesVocabulary

Exercise 4:

1. grafting

2. budding

3. scion

4. stock

5. limb

6. furnish

7. propagate

8. species

9. ornamental trees

10. deciduous trees

11. dormant

Exercise 5:

1. cambium layer

2. chip

3. cleft

4. slanting

Key to ExercisesVocabulary

Exercise 6:

1. εισάγω

2. κάμβιο

3. αυτός που αναπαράγεται

Exercise 7:

1. scion

2. stock

3. orchardists

4. dormant

5. minimum

6. tongue

7. cleft

8. limbs

9. retain

10. although

11. supplied