22.1 Natural Cloning In Plants

Question 1

what is cloning?

Answer 1

The process of producing genetically identical cells or organisms from the cells of an existing organism.

Cloning can occur naturally in some plants and animals, but can also be carried artificially

Question 2

Describe and explain vegetative propagation

Answer 2

Some plants can produce natural clones by vegetative propagation — this is the production of plant clones from non-productive tissues e.g. roots, leaves and stems

It is a type of asexual reproduction

Question 3

Different types of natural vegetative propagation methods?

Answer 3

• rhizomes (e.g. marram grass): these are stem structures that grow horizontally underground away from the parent plant. Buds develop and form new vertical shoots which become independent plants.
• runners (e.g. strawberry or spider plant): a lateral stem grows away from the parent plant and roots develop where the runner touched the ground and a new plant develops
• bulbs (e.g. daffodil, onions): leaf bases swell with stored food from photosynthesis. Buds form internally which develop into new shoots and new plants in the next growing season
  Underground food stores used by some plants, new bulbs develop from original bulb and form new individual plants.
• stem tubers (e.g. potato): large underground plant structures that act as a food store for the plant. Buds on the storage organ develop to produce new shoots (e.g. ‘eyes’ on the potato)

Question 4

How is vegetative propagation used in horticulture and agriculture? Examples?

Answer 4

Horticulturists (plant growers) and farmers can exploit a plant’s natural ability to produce clones.
By manipulating the way in which a plant grows, they can induce vegetative propagation, so they can get natural clones of the parent plant.

Methods:
- they can take cuttings
- they can use grafting — joining the shoot of one plant to the growing stem and root of another plant
- they can use layering — bending a stem of a growing plant downwards so it enters the soil and grows into a new plant

Question 5

Describe and explain the steps to produce clones from cuttings

Answer 5

Growing plants from cuttings is a really simple way to make clones of a parent plant

How a cutting can be taken and grown from a stem:
1) use a scalpel to take a cutting (between 5-10 cm long)
2) remove the leaves from the lower end of your cutting, leaving just one at the tip
3) dip the lower end of the cutting in rooting power, which contains hormones that induce root formation
4) then plant your cutting in a pot containing a suitable growth medium (e.g. well drained compose)
5) provide your cutting with a warm and moist environment by either covering the whole pot with a plastic bag or by putting it in a propagation
6) when your cutting has formed its own toots and is strong enough, you can plant it elsewhere to continue growing

You can also take cutting from other parts of the plants (e.g. root or leaf):
- to take a root cutting, cue a piece of the root from the plant with a scalper, then remove uncut end of the root with a slanted cut. Then dip the cutting in rooting powder

• for leaves, split vein cutting is used, score large veins on the lower leaf surface using a slacked and put it on top of the growth medium. A new plant should form from each break in the veins

Question 6

Factors that increase the success rate of most cuttings?

Answer 6

• use a non-flowering stem
• make an oblique (slanted) cut in the stem
• use hormone rotting powder
• reduce leaves to two or four
• keep cutting well watered
• cover the cutting with a planting bag for a few days

Question 7

What are perennating organs and how are they involved in cloning and survival?

Answer 7

Organ which contains stored food from photosynthesis
E.g. potato
Cloning - bud may arise from the organ which develops into a new shoot
Allows plant to survive adverse conditions

Question 8

Explain advantages and disadvantages of propagating crop plants by cuttings over using seeds

Answer 8

Ad:
- cuttings are genetically identical to parent so likely to produce good crops
- shorter time from planting to crop
- reliable

Diad:
- seeds have genetically variation, so more variety in quality of crop but are more likely to withstand changes in environment (e.g. diseases)