User:Filippendo/Bur

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The main function of the bur is to spread the seeds of the bur plant, often through epizoochory. The hooks of the bur is used to catch on to for example fur or fabric, so that the bur, which contain seeds, then can be transported along with the thing it attached itself to. Another use for the spines and hooks are physical protection against herbivores. Their ability to stick to animals and fabrics has shaped their reputation as bothersome.

The number of burs per fruit along with the size and shape can vary largely between different bur plants.

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Containing seeds, burs spread through catching on the fur of passing animals (epizoochory) or machinery as well as by being transported together with water, gravel and grain.

Spinescent plants repel herbivores mechanically by wounding the herbivore's mouth or digestive system. Moreover, burs' mechanical defence can work alongside the color of the bur that can visually warn off herbivores.

The bur must be able to easily detach from the plant and easily attach to for example the fur of an animal. The ability to spread the seeds depends both on the number of burs that manage to get attached and on force of attachement. The hook span of the bur has been shown to have a large influence on the contact separation force. Some studies have also shown force can increase with the size of the birr, although not all large burs have a high contact separation force. Furthermore, the flexibility of the bur might also influence this force which can increase with stiffness.

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Furthermore, because of their ability to compete with crops over moisture and nutrition, bur plants can be lableled as weeds and therefore also be subject to removal. Methods of controlling the spread of bur plants include the use of herbicides, slashing and cultivation omong other.