Take a moment and imagine that you live in the Sahara desert. Not in a house, or a tent, but out in the elements, surrounded by the sun, sand and vultures. Now imagine that the only water you have access to in your desert oasis is rainwater. Knowing that most areas of the Sahara desert receive less than 2 cm of rain a year, would you be worried about not getting enough water? You should be! What would you do to make sure that you didn’t end up dehydrated? Well, if you’re a plant (or at least have plant-like skills), you’d produce a protective layer with a wax-like textured called a cuticle.
Did you know? When humans sweat, most of what is released is water, this is an attempt to cool the body. If you do not replenish this water, you end up dehydrated which is why you get so thirsty when playing sports.
Plant and animal bodies are multi-layered. The most exterior part of this arrangement is the epidermis . In humans, we call this outer layer our ‘skin’. In plants, this ‘skin’ is of vital importance as it protects the plant from desiccation (drying up), uv radiation and foreign particles (viruses, insects, and anything else that may harm the plant). Most of this protection is provided by the plant cuticle which is excreted by the epidermis. The cuticle is a continuous membrane that covers the portion of a plant that is in the air. The waxy cuticle contains hydrophobic hydrocarbons called cutin and wax, these hydrocarbons are what make the cuticle ‘waterproof’, preventing water from getting in or out.
Did you know? Hydrophobic means ‘afraid of water’. The next time it rains take a look at the beads of water that form on plant leaves, this is an example of the hydrophobic cuticle repelling the water and preventing it from entering the plant.
Because of the impermeability of the cuticle, plants need to have cells that allow them to exchange gases with their surroundings. In humans this exchange is called respiration and involves exhaling carbon dioxide and inhaling oxygen. Plants do much the same thing by a process called photosynthesis which involves the release of oxygen and the uptake of carbon dioxide. Instead of having mouths, plants breathe through their stomata . The epidermis of a plant must have ‘spaces’ in it for these stomatal cells, these spaces are in different locations on different plant species making every plant’s epidermis unique! It is similar to the pores on your skin; your pores are not in the exact same spots on you as they are on your best friend. Because of this unique surface pattern of plants, each plant has its own fingerprint, allowing botanists to identify and classify the type of plants that were in an area long after the plant has died.
Did you know? In humans our finger prints are completely unique. Though plant fingerprints are sometimes unique to the individual, most often they are unique to a particular plant taxon or group.
The evolution of the plant cuticle is one of the most important adaptations in plants. Lucky for us, we can walk and think which makes it a lot easier to locate water when we need it. But if you’re ever stuck in the Sahara, you may want to think about using your ear wax as sunscreen!
This answer was researched and written by Crystal Vincent, a masters student at the Ottawa-Carleton Institute of Biology. She has pet walking sticks and she doesn’t like yogurt.
Learn More! Shoot Apex and Leaves Plant Cuticles