Intermediate Level

Cloning a living organism

Introduction

In this procedure, students clone a plant by taking cuttings. A closer look at the cuttings a few weeks later could reveal which characteristics of each cutting depend on the genetic make-up of the plant and which are strongly affected by environmental conditions.

Lesson Organisation

Demonstrate how to take the cutting. If you plan to use the same material with your teaching group each year, take some digital photographs to make giving instruction easier next year. At the end of this lesson, each student will have prepared a cutting to take home. Review how these have grown after a few weeks. Because each cutting has been treated differently, there is scope to evaluate the protocol and consider how to improve it. You might want to debate the ethics of cloning in this lesson, or at a later date when you have explored some of the other methods of cloning.

Apparatus And Chemicals

For the class – set up by technician/ teacher:

Plants from which cuttings can be taken – busy lizzie (Impatiens) and pot geranium (Pelargonium spp) are ideal.
Rooting powder, labelled A, any proprietary brand, 1 tub
Rooting powder, labelled B, icing sugar or fine sand, a similar quantity (See note 1.)

For each group of students:

White tile, 1
Scalpel, 1
Plant pot, 10 cm diameter, 1
Compost, enough to fill the pot
Plastic bag, 1
Beaker, 100 cm³, 1
Magnifier or hand lens, 1

Health & Safety

Read our health and safety guidelines

• Refer to manufacturer’s guidance on the packet of rooting powder.
• Some people may find that plant sap irritates their skin.
• Take care with sharp cutting tools.
• Wash hands after completing the work

Technical Notes

1 Although rooting powder does contain hormones that could promote rooting, there is some evidence that the main way it promotes formation of cuttings is by its fungicidal action. This is very hard to test, but it might be interesting to see if it has any detectable effect at all, by comparing cuttings treated with and without rooting powder.

Ethical issues

There are ethical issues associated with more advanced cloning technologies – especially those involving animal material including cloning animal material from adult cells. However, most people do not find there are issues with cloning plant material in this way. There is a risk of reduction in biodiversity, and hence an increase in vulnerability of ecosystems where a large area is populated with identical cloned material.

Procedure

SAFETY: Always carry scalpels on a white tile, with the blade on the tile and pointed away from you.

Preparation

a Ensure you have enough cutting material for each student (or pair).

b Buy some proprietary rooting powder and make up a substitute powder (see note 1).

Investigation

a Collect a pot filled with compost, a white tile and a scalpel.

b Cut off a non-flowering stem from the plant to be used. Choose a section about 10 cm long.

c Trim the cutting by removing all but the top pair of leaves, or the top two pairs. Cut through the stem at an oblique angle at one of the places where you have removed some leaves.

d Take a close look at the end of the stem. Use a magnifier.

e Choose which rooting powder to use.

f Dip the cut end into the rooting powder and then push it firmly into the middle of the compost, so the cut end is at least 3 cm under the surface.

g Collect a plastic bag and a small beaker of water.

h Put the pot in the bag. Pour in the water. Seal the bag.

i Take the cutting home and keep it moist – but not soaking – in water. You can take the bag off after 2-3 days, and leave the cutting on a saucer on a windowsill. Keep watering every 2-3 days.

j Make notes of the features of the original plant.

k Keep the original plant for comparison if it has not been entirely used up in making cuttings.

l Collect observations of the cuttings after 2/3 weeks (or more) to compare with the original plant.

Teaching Notes

Some of the features of the cutting – for example leaf shape, leaf colour, flower colour (revealed as the cutting develops) – depend on the genetic make-up of the plant. Other features – for example number of leaves, height of cutting – are strongly influenced by environment. As all the cuttings have been kept in different conditions (students’ home windowsills) there should be significant variation in the features affected by environment and no variation in the features determined by genetics.

Taking cuttings is a simple method for producing large numbers of plants with the same genetic composition. This can be valuable in commercial production of plants in demand for horticulture, particularly rare plants such as orchids.

Plants occasionally produce ‘sports’ – when a mutation in the growing tissue changes a characteristic of the plant. This might result in a single branch with significantly different leaves, flowers or fruit from the rest of the plant. Taking cuttings from a branch of this type could produce several plants in a short time.

Plants grown from cuttings will be genetically identical to one another and the parent material whereas plants grown from seed show significant variations.

Health and safety checked, September 2008

Downloads

Download a student sheet with questions and answers here (51 KB).

Web Links

http://www.beep.ac.uk/content/345.0.html
BioEthics Education Project: “beep”. Visit this site and the Cloning part of the Genetic technology section for more information and guidance on how to debate the ethical issues.

http://www.rhs.org.uk/Advice/profiles0800/propagating_tender.asp
Royal Horticultural Society instructions for taking cuttings from bedding geraniums (Pelargonium). The RHS website has guidance for propagating all kinds of plant material.

(Websites accessed September 2008)

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