Next time you step outside, take a moment to notice all the plants. You may see a grassy lawn, weeds poking through the sidewalk, towering trees, moss growing on rocks or bricks, or maybe even a vegetable or flower garden. Now let this thought sink in: without plants, you and all the other human beings and animals on this planet couldn’t survive. We depend on plants for the air we breathe. But the relationship goes much deeper than that. We also rely on plants for food, clothing, medicines, materials, and so much more.
Plants Feed and Nourish Us
Plant cells have an important feature that animal cells lack: chloroplasts. The chloroplast is a small, green structure inside a plant cell that captures energy from the sun and turns it into sugars that the plant uses to grow. This process, called photosynthesis, releases oxygen as a by-product. Humans and other animals breathe that oxygen.
Humans and most animals need plants in their diets, too. Corn, wheat, rice, cabbage, apples, grapes, and hundreds of other grains, vegetables, and fruits taste delicious. But eating plants isn’t just something we do for fun . The chloroplasts in plant cells produce important compounds that human and animal bodies need in order to survive . These compounds include amino acids, the building blocks of proteins, and vitamins.
Over millions of years of evolution, as our animal ancestors fed on plants, their bodies gradually forgot how to make some of these compounds. The only way for people to get essential amino acids and most vitamins is from a diet that includes plants (or the meat of animals that ate plants).
The human body needs twenty- one types of amino acids in order to build all of the proteins it uses to function and stay healthy. The body can make most of these amino acids itself, but nine essential amino acids come only from protein in the diet. A food with “complete protein” contains all of the essential amino acids . All meats and dairy products, such as pork, eggs, and milk, are complete proteins. However, plants are still the ultimate source of the essential amino acids. The pigs, cows, and chickens that these products come from ate a variety of different plants to acquire the essential amino acids.
Some plants, including quinoa, soy, and spiru lina contain all nine essential amino acids . Most plants are missing one or more of them, but a diet that includes a variety of plants will provide all nine. Rice and beans, a staple dish throughout Latin America, provides complete protein.
Chloroplasts also produce many of the compounds that the human body needs to stay healthy. Vitamin A, for example, is essential for healthy vision and reproduction and for a strong immune system . The body makes Vitamin A from beta – carotene, a compound that forms in the chloroplasts of colorful fruits and vegetables such as carrots, mangoes, and kale. Meat, fish, and dairy products often contain Vitamin A as well.
Animal products do not contain all the essential vitamins, though. Vitamin C only comes from fruits and vegetables, especially citrus fruits, tomatoes, potatoes, and bell peppers. (Raw liver and fish eggs provide some Vitamin C, but the vitamin is much more plentiful and common in plants.) The body uses Vitamin C to grow new cells and repair damaged areas . If a person doesn’t get enough Vitamin C, he or she will develop a disease called scurvy . If left untreated, scurvy is deadly. Interestingly, cats, dogs, and many other animals can make their own Vitamin C, but most primates, most fish, and some other animals cannot.
Plants Keep Us Healthy
Many of the products that keep you healthy come from plants. Soaps and other cleaners often contain plant oils. Aspirin is made from willow tree bark. Quinine, one of the earliest treatments for malaria, comes from the bark of the cinchona tree, which is native to South America. The spices turmeric and ginger, which can also be used as medicines, come from plant roots.
In the world of medicine, synthetic drugs are the most common kind. But the natural world is a very important source of ingredients and inspiration. Plants contain a vast diversity of chemical compounds that human chemists can’t imagine or create on their own. In 2019, 25 percent of the world’s medicines came from plants. Some plants are used directly to treat diseases, but in most cases, drug developers first isolate chemical compounds from plants. Then they use those compounds to manufacture a medicine.
Taxol, the brand name for a drug that treats several forms of cancer, including breast cancer, is one of the best-selling cancer drugs of all time. The drug stops cell division, so cancer cells can’t grow and spread. Its main ingredient is a compound from the bark of the Pacific yew tree . Unfortunately, these trees are not common and grow very slowly. Extracting enough of the compound to treat just one patient requires six of the trees. So researchers found a way to use the needles and twigs of a closely related tree to make a semi- synthetic version of the drug.
Artemisia annua, a fern-like plant with tiny yellow flowers, is commonly known as qinghao, sweet wormwood, or sweet annie. Chinese people had long used the plant as medicine. Then, in the twentieth century, scientists figured out how to isolate the compound artemisinin from the plant. The World Health Organization approved the compound as a treatment for the disease malaria in 2001. In 2017, Pamela Weathers of the Worcester Polytechnic Institute in Massachusetts showed that tea o r tablets made from dried leaves of the plant could deliver forty times more artemisinin than typical drugs that contain the purified compound plus other ingredients that help fight the disease. “The people who have malaria are some of the poorest people on the planet,” says Weathers. “They can’t afford to buy these combination drugs.” She showed that using the dried leaves can be a much cheaper yet also effective treatment.
Artemisinin is one example of a terpene, a huge class of chemical compounds produced by plants. Over sixty thousand of these compounds have been identified in nature. Terpenes give plants their smells, tastes, and colors. All terpenes contain two or more isoprenes linked together into a chain. A single isoprene is a compound containing five carbon and eight hydrogen atoms . (Regular isoprene happens to be the main ingredient in both natural and synthetic rubber.)
Taxol, quinine, caffeine, and nicotine are all terpenes . Common plants that produce terpenes include tea, thyme, and citrus fruits. The most abundant one is myrcene, which is also found in basil and mangoes. It can have a calming or sedative effect. Another common one is limonene, which also gives citrus fruits their distinct smell. It kills bacteria and fungi and also smells good, so it’s a common ingredient in many household cleaners and makeup products.
In the future, medical researchers will continue to seek inspiration and knowledge from plants and the rest of the natural world.
Plants Inspire New Technology
You use plants for much more than just food and medicine. Cotton, linen, and rayon are woven into t-shirts, blue jeans, socks, sheets, rugs, and other textiles . Paper and wooden beams for building come from trees . In all of these materials, cellulose provides shape and structure. Cellulose is a tough material that makes up the walls of plant cells. There is more cellulose on Earth than any other organic compound. In food, cellulose is called fiber. The human body can’t digest it, but fiber helps feed the bacteria in your intestines so they can keep your body working properly.
Today, researchers are turning cellulose into materials that act like plastic but are much friendlier to the human body and to the environment. Unlike plastic, cellulose materials break down easily. But they can also be strong and sturdy. Researchers can isolate nanometer-sized rrods of cellulose, also called nanocellulose, from many types of trees, algae, and other plants. A material made from nanocellulose is very lightweight, strong, and absorbs liquid. Plus, it is green and renewable. Researchers have been finding numerous uses for the material in medical devices, glues, electrical components, batteries, textiles, paper products, and more.
Plants, in the form of biofuels, can also power our technology. Using biofuels helps reduce the amount of fossil fuels we need to burn. That’s a good thing since fossil fuels pollute the environment and worsen climate change.
The most common biofuel is ethanol, which is mixed with gasoline to power cars and other engines. To make ethanol, manufacturers put large amounts of plants into vats and then add bacteria or yeast to turn the sugars in the plants into ethanol. This process, called fermentation, is also how beer, wine, and other alcohols are made.
Biodiesel is another biofuel. It’s made from vegetable oil or animal fats. Used cooking grease can be turned into biodiesel. One problem with biofuels is that most manufacturers use food crops to produce them . So those crops can no longer feed animals or humans. Researchers are working on ways to instead make biofuels from plant waste, such as sawdust and cornstalks, or from extremely common or invasive plants like algae or weeds.
The structures of plants can inspire technology too. In a famous story, inventor George de Mestral created Vel cro afte r carefully observing burrs that had stuck to his clothes and his dog’s fur. This type of inspiration still happens today. Claudia Zeiger, a researcher at Karlsruhe Institute of Technology, investigated two types of plants that could help clean up oil spills. Salvinia leaves, she says, repel water and absorb oil, thanks to a complex surface structure made of tiny, interconnected hairs. “You could just collect those leaves and use them as a natural oil solvent,” she told Physics World. Or engineers could create materials with a similar structure.
Lotus plants also have a fascinating structure. It repels water and dirt. If people could recreate this coating, we could use it to make clothes that rarely need washing.
Plants keep us a live, feed us, clothe us, heal us, and inspire us . What else could plants do to help humans? That’s up to the next generation of scientists and engineers to discover.
