Plant Cloning Flashcards
What is cloning?
-The process of producing genetically identical cells or organisms from the cells of existing organisms
-it can occur naturally in some plants and animals but can also be carried out artificially
What is vegetative propagation?
The production of plant clones from non reproductive tissues e.g roots, leaves, stems
Give 3 examples of natural vegetative propagation methods that plants use
1) Stolons or runners used by strawberries = stem structures that grow above ground on the surface of the soil. New shoots and roots can either develop from nodes or form at the end of the stolon
2) tubers used by potatoes= large underground plant structures that act as a food store for the plant. They’re covered in ‘eyes’ which are each able to sprout and form a new plant
3) bulbs used by onions = underground food stores used by some plants. New bulbs are able to develop from the original bulb and form new individual plants
What other ‘natural’ methods of vegetative propagation can plant growers use to produce clones?
-taking cuttings
-grafting (joining the shoot of one plant to the growing stem and root of another plant)
-layering (bending a stem of a growing plant downwards so it enters the soil and grows into a new plant)
Explain the steps for making a plant clone from a cutting
1) use a scalpel to take a cutting from then end of a stem of your parent plant with an oblique cut (maximises large surface area)
2) remove the leaves from the lower end of the cutting (minimises transpiration)
3) dip the lower end of the cutting in rooting powder which contains hormones that induce root formation (encourages growth)
4) plant cutting in a pot containing a suitable growth medium
5) provide your cutting with a warm and moist environment by either covering the whole p with a plastic bag or by putting it in a propagation (reduces transpiration rate)
6) when the cutting has formed its own roots and its strong enough you can plant it elsewhere to continue growing
Explain the technique of tissue culture used to artificially clone from existing plants
1) cells are taken from the original plant that’s going to be cloned
2) cells from the stem and root tips are used because they’re stem cells (this is the explant)
3) the explant is sterilised to kill any microorganisms (bacteria and fungi compete for nutrients with the plant cells which decreases their growth rate)
4) cells are placed on a culture medium containing plant nutrients like glucose and growth hormones like auxins
5) callus forms (a group of undifferentiated cells)
6) it is transferred to a root inducing medium, then a shoot inducing medium
7) plantlets form (tiny genetically identical plants) they’re taken out of the medium and planted in soil
8) acclimatised before planting outside
Explain why tissue culture may be used
-to clone plants that don’t readily reproduce or are endangered or rare e.g British orchids
-also used to grow whole plants from genetically engineered plants
-micropropagation is when tissue culture is used to produce lots of cloned plants very quickly
What are the arguments for artificial plant cloning?
-desirable genetic characteristics are always passed on to clones. This doesn’t always happen when plants reproduce sexually
-allows plants to be reproduced in any season because the environment is controlled
-less space is required by tissue culture than would be needed to produce the same number of plants by conventional growing methods
-it produces lots of plants quickly compared to the time it would take to grow from seeds
What are the arguments against artificial plant cloning?
-undesirable genetic characteristics are always passed on to clones
-cloned plant populations have no genetic variability, so a single disease could kill than all
-production costs of tissue culture are very high due to high energy use and the training of skilled workers, so it’s unsuitable for small scale production
-contamination by microorganisms can be disastrous and result in complete loss of the plants being cultured
