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Another exam question commentary: Level 3 Plant Growth
by Janet Prescott - Tuesday, 21 April 2020, 10:12 AM

From February 2019, Unit 3104.


a)      State what is meant by EACH of the following terms:

i)                 micropropagation;                                                2 marks

ii)                totipotency.                                                            2 marks


b)     Decsribe EACH of the following processes of micropropagation:

i)                 maintaining sterile techniques;                          2 marks

ii)                weaning off.                                                           3 marks


c)      State ONE situation where micropropagation is used in commercial horticulture. 1 mark

This question relates to the following part of the syllabus:

Outcome 2

 Understand the relevance of anatomy, physiology and environmental factors to methods of vegetative propagation.

 2.3 Describe the propagation of plants by micro-propagation. 

State what is meant by the terms ‘micropropagation’ and ‘totipotency’.

 Describe the processes of micro-propagation to include: plant material; facility and growth media; sterile techniques; weaning off.

 State the uses of micro-propagation in commercial horticulture, to include: propagation of difficult plants, rapid multiplication of stock, production of virus free stock.


Part a) is directly from the first part of 2.3, so a straightforward question. The examiners’ comments suggest the following as suitable definitions:

i)                  ... the production of clonal explants by growing very small sections of meristematic plant tissue, in sterile controlled conditions in a suitable container, using sterile nutrient growing medium with added growth hormones.

ii)                ...  the ability of an individual cell possessing genes/DNA/genetic material, to divide and differentiate producing other cell types, resulting in a complete new plant.

These are fairly detailed definitions, particularly for part i).

For part b)i)  the examiners’ comments point out that some parts were missed, such as the use of an autoclave to sterilise the media and equipment; the use of a laminar flow cabinet, flaming the dissection and transfer equipment and wearing appropriate personal protective equipment.

For part ii) the examiners’ comments describe weaning as a procedure of gradually reducing temperature and relative humidity, applying ventilation and raising light levels, to acclimatise propagules to the brighter, cooler, drier conditions outside the laboratory.

A suitable answer for part c) is suggested as the propagation of plants difficult to do by other methods, such as orchids; increasing plant numbers quickly from small amounts of material and producing virus free plants from meristem tip culture.

This is a question where you need to understand the technical terms. The questions are very straightforward from the syllabus, but it can be seen that a good amount of detail is required in the answers to gain higher marks.