When plants arrived on this planet around 500 million years ago, they set some things in motion.

Spores, and later seeds, completed epic journeys of reproduction — and the domain of plants grew and grew. Flowers and fruits of all shapes and sizes emerged, and coevolved with more types of animal life than had ever been seen before.

And much, much later, we showed up. Plants are our elders, and there is power in paying attention to them. Our relationship with plants has shaped nearly every arena you can think of, from farming to shelter to medicine and beyond.

And over the years that we’ve been studying, and wearing, and living inside, and eating plants — we’ve learned some stuff. We’ve peered into their cells, uncovered how they cycle nutrients, traced their chemicals and hormones, and even modified some of their genes. But here’s the thing: plants still have secrets up their leaves.

And as the big field of botany expands, what we learn next could even help us tackle some of the planet’s biggest challenges. So get out your Magic 8 balls because today, we’re looking into the future. Hi, I’m Alexis, and this is Crash Course Botany.

Will I be an excellent host today? [gasps] It is decidedly so! [THEME MUSIC] There are lots of botanical mysteries still to be solved — many, not for lack of trying. Like, take this age-old question we’ve been asking for millennia: Can plants feel? Over two thousand years ago, the Greek philosopher Aristotle thought the answer was “no.” He believed that was what set plants apart from animals.

That plants had no senses, no ability to react or perceive things. Much later, in the 1960s and ‘70s, a former CIA interrogator-turned- amateur-botanist had a totally different take. He hooked a plant’s leaves to a polygraph machine, and later published a book on the results.

He argued that plants could not only feel their own emotions, but could pick up on people’s too. Since then, we’ve come to understand that neither perspective was quite right. Without a brain or pain receptors, there isn’t evidence that plants feel in the way we think of it.

But plants do have ways of sensing and reacting to information in their environment. Sometimes those responses are recognizable and action-packed — like a Venus flytrap snapping shut on a bug. But more often, evidence of plants’ senses unfolds internally.

So we’re still working out the nuances. Like, there’s mounting evidence that plants respond not just to light, touch, and gravity, but also to odors. And they might even be able to hear stuff …sort of.

We know plants can sense vibrations directly on their leaves, like a caterpillar chewing. But we’re still figuring out whether plants react to the vibrations of sounds. In one experiment, plants exposed just to the sound of chewing caterpillars released chemical defenses.

That could mean the plants detected the vibrations and interpreted them as a threat. And there’s another way plants might communicate: through their roots. Roots secrete lots of carbon-based molecules, and plants might use some as signals to warn other plants about poor conditions.

Like, in one study, researchers took a bunch of maize plants and let them grow for a bit in little nutrient baths. And some of the plants got a special treatment— the researchers gently ran a soft face brush over them for one minute every day. Ahh… this kind of touch is actually pretty uncomfy for plants, though.

It was meant to simulate them brushing against each other, which can cause stress, kind of like being squeezed next to your siblings on a long car ride. Then, the researchers took those nutrient solutions that the maize plants were bathing in and gave some fresh, baby maize plants a choice. They could either grow in the direction of A) the nutrient solution from the plants that did get touched or B) the solution from plants that didn’t get touched.

The babies chose B—suggesting they were picking up on stress signals secreted from the roots of the touched plants into the solution. But we’re still working out the details of this root communication thing. Like, some scientists suspect that trees share resources and communicate through a network of fungi spanning their roots.

A wood-wide web, if you will, which might help forests cooperate by shuttling resources from older trees to younger ones. But others think it’s more likely the fungi are running the show— moving resources around based on what works best for them. In the future, with more research, maybe we’ll solve these mysteries and others.

Like, as far as we know, plants have only ever sprouted naturally in the soil on Earth. But there might be other possibilities, and a frontier where no plant has ever grown before. Let’s head to the Thought Bubble… In the late ‘60s and early ’70s, when the Apollo missions launched astronauts to the moon and back, they returned with stories of cratered terrain, awe-inspiring images of Earth from space… and heaps of moon dirt.

That dirt sparked a burning question in the hearts of botanists and space teams alike: “Could we someday garden in this stuff?” The bad news: moon dirt isn’t like most soil here on Earth. It has very little of the chemicals nitrogen and phosphorus that plants need. And, it’s riddled with shards of glass and metallic iron.

Not a great nursery for a baby plant. But that hasn’t stopped science! In 2022, after decades of experiments using imitation moon dirt made from volcanic soil, NASA finally gave some researchers the go-ahead to try gardening in their precious, real moon dirt.

So the researchers planted Arabidopsis, a hardy little plant, in twelve pots of real moon dirt and sixteen pots of the fake, Earth-made moon dirt for comparison. All of the plucky Arabidopsis seeds did sprout and grow. But they fared much better in the soil from our own planet.

In moon dirt, the plants were smaller and purplish, a surefire sign of stress. They also turned on genes that plants usually activate only when they’re dealing with too much salt or metal. So if farming on the moon is going to be in our future, we might need to genetically engineer plants to be more moon-tolerant, or modify moon dirt to be more plant-friendly.

And it will take a lot of work to get there. But if lunar gardening ever gets off the ground? It’ll be one small step for plant, one giant leap for plantkind.

Thanks, Thought Bubble! Of course, here on Earth, we’ve got other burning questions to attend to —like, how do we combat climate change? Tackle global health challenges?

And feed a growing world population, expected to reach 10 billion by 2050? Luckily, we don’t have to look to outer space to start answering them —we can begin right here. Like by linking the past few hundred years of Western plant science with traditional knowledge from communities around the globe.

There are so many valuable ways of knowing that have been formed through observations passed down over many generations. The diverse field of ethnobotany studies how various cultures have used local plants in their food, shelter, clothing, medicine, and more. For example, ethnobotanists found that in one community of Buyi people in China, locals make medicines using over 120 different plant species —many of which have never been studied for their medicinal properties in a laboratory.

And that’s just one example from one particular culture. But it offers a glimpse into how much more there is to learn if we respect and include a variety of ways of knowing. In many places, traditional knowledge of plants is in danger of disappearing— and so are the plants themselves.

By understanding how people rely on local plants, future research can identify which species are top priorities for conservation. Ethnobotanists can also work to protect traditional knowledge itself. For example, ethnobotanist Rose Bear Don’t Walk focuses on sharing knowledge of edible plants from her Salish culture —a grouping of Indigenous Peoples from the Western U.

S. and Canada. By crafting a Salish food curriculum and field guide for schools, Rose Bear Don't Walk could even help younger generations stay connected to the plants their ancestors ate. And for all humanity’s creativity in the kitchen, we’ve got a problem of not enough diversity of crops in our food systems.

Worldwide, we get most of our calories from just three crops: maize, rice, and wheat. By farming just a handful of species, we’re missing out on a smorgasbord of other options— an estimated seven thousand plant species out there that also make for good eating. This lack of food diversity leaves many populations vulnerable to hunger when their major crops fail, or malnutrition when these crops aren’t paired with other, more nutrient-rich foods.

Meanwhile, there are other plant MVPs waiting on the sidelines. Entering the field… the high-protein, the drought-resistant African yam bean! It grows when other crops can’t, thanks to its ability to lock nutrients into the soil.

And it doesn’t need fertilizers, which can leach harmful chemicals into nearby waterways. So by connecting to traditional knowledge, future botanical research may help bring under-used plants onto the menu. Plants may also play a supporting role as we tackle humanity’s biggest challenge to date: climate change.

Burning fossil fuels for energy releases most of the gases that are warming our planet to dangerously high temperatures. But in the future, we’re likely to scale up our production of biofuels made from food waste —a renewable energy source that releases far less carbon dioxide. And plants may help reduce other gases, too.

Raising cattle for meat and milk currently accounts for nearly half of the global emissions of methane— a warming gas with twenty-five times the heat-trapping power of carbon dioxide. But the future could bring more plant-based substitutes to help us cut back. So you can have your low-methane milkshake and drink it, too.

As climate change becomes an even more urgent issue, we can study its effects in the wild, in conservation parks, and in magical places like botanical gardens and herbaria, which are home to plant species from all over the world. Herbaria in particular preserve plants from hundreds of years ago and let us see how changing conditions have affected them over the course of history. OK, maybe there isn’t a Magic 8 ball that can really foretell botany’s future.

But by studying the plants of yesterday and today, we can face this era of uncertainty— and shape what happens next. The future of botany depends on making room for more voices and ways of knowing. We can ask new questions, gain new insights, and make shared discoveries by bridging knowledge across cultures.

And as we keep probing plants’ mysteries, we can rely on the same tool we’ve always had, tried-and-true for millennia: our attention. Thank you for giving us yours throughout this series. And we hope you’ll keep it finely tuned, so you never miss the plant drama unfolding all around you.

Hey, before we go, let’s branch out! What plant’s seeds were the first sent to, and recovered from, space? I’m not saying the answer is corny, but look for it in the comments!

Thanks for watching this episode of Crash Course Botany which was filmed at the Damir Ferizović Studio and made in partnership with PBS Digital Studios and Nature. If you want to help keep Crash Course free for everyone, forever, you can join our community on Patreon.