What determines the number of spines on a holly leaf?

Produced by Science & Plants for Schools (SAPS), this activity enables students to:
•    develop knowledge and understanding of structural defence mechanisms in plants
•    develop problem solving skills
•    demonstrate the processing of information and use of calculations

The investigation looks how the number of spines on holly bush leaves varies with height from the ground. The investigation provides a good opportunity to collect data and process it appropriately. Once dried, specimen leaves should last for several years.

Although it is generally accepted that the higher up the leaves the less spines they will have, the relationship is not always straightforward. The number of spines produced varies from one variety to another. Also, constant pruning, for example to produce a hedge, appears to increase spine production.

The investigation is designed for students following a Scottish Highers course but it is equally useful for other post-16 courses in biology. It could also be adapted for secondary students of a younger age.