Trichomes make a plant feel at home
One of the most obvious differences between plants and animals is that plants don’t move very much. This can be a major disadvantage as it means that they can’t escape predators or relocate when the environment around them becomes unfavourable. However, coping with this type of lifestyle has resulted in a range of clever adaptations.
An example of one of these adaptations is the evolution of trichomes. These are tiny outgrowths from the plant which look like tiny hairs or small glands. Trichomes can be various shapes and sizes, and have a whole range of different adaptations.
For instance, stinging nettles are covered in tiny hair-like trichomes which the plant uses to stop herbivores from eating it. Close up they look like very sharp, tiny, hollow needles. When something brushes against the leaf, the trichome needles break and inject the skin with a cocktail of compounds including histamine, acetylcholine and serotonin. These chemicals are responsible for the stinging nettle “sting” and uncomfortable allergic reaction afterwards.
Other plants, such as the carnivorous pitcher plants have evolved trichomes to help trap insects which they then digest. The inside of the pitcher plant is lined with downward facing spines which get slippery when wet. These make it easy for unsuspecting insect prey to slide down into the deadly mixture below, and almost impossible for them to escape back out.
Some of the best known examples of trichomes are found on cannabis plants. The possible function of these was recently explained in a talk at the Society of Biology by GW Pharmaceuticals’ Director of Botanical Research and Cultivation, Dr David Potter. Dr Potter explained that these gland-like trichomes produce a complex mixture of sticky smelly chemicals known as cannabinoids. It is thought that the plant releases these compounds to trap insect predators, preventing them from eating the leaf or spreading disease to the plant. One of the cannabinoids made by the plant, called tetrahydrocannabinol (THC), is also extracted and used to give recreational drug users a “high”.
These are only a few examples of the diverse way in which plants have adapted trichomes to specifically help them survive in a stationary environment. Many other forms exist with equally diverse functions including waterproofing, preventing water loss and protecting the delicate plant leaves from damage by solar radiation.
Image by Anna Tiley