All I Really Need to Know I Learned in the Duke Greenhouses

April 4, 2023
Science Magazine

As anyone who’s ever taken a late-night final at Gross Hall knows, the Duke Greenhouses are the glowing gem of Science Drive. Nested between the Biological Sciences building and the French Family Science Center, the Greenhouses provide over 15,000 square feet of space and state-of-the-art climate control technology to more than 800 species of plants from all over the world. As a lifelong treehugger who decided to study molecular biology, I’ve often wistfully gazed at the greenhouses from afar, wondering what treasures are held behind their glowing glass walls. This semester, I found out. I had the amazing opportunity to take a tour of the Greenhouses with Professor Paul Manos as part of his Organismal Evolution course, offered every spring. If you’ve ever wondered about the Duke Greenhouses, get ready: I’m here to tell you all about them.

Above: The Duke Greenhouses are the heart of plant biology research at Duke. Their teaching collection also provides an opportunity for undergraduates to learn about plant biology and diversity through coursework and labs in the Biology department. Courtesy of Katherine Long.

Our tour began with Dr. Manos leading the group into the Greenhouses through the researchers’ entrance, giving us a firsthand look at what the botanical scientists of Duke see every day. As we entered the long glass hallways adjacent to the plant rooms, I looked around to see computer stations covered in plant posters and print-outs of science jokes, not unlike what my cancer research lab has on our front door. Researchers milled about carrying clipboards and plant cuttings; several said hello to us. 

Dr. Manos began the tour by showing us a student-made poster of what he calls the “Green Tree of Life”: a phylogeny of plants from their algal ancestors to the flowering angiosperms currently in bloom all over campus. Plants originated from algae, the slimy green stuff that you’ve likely encountered in oceans and lakes. About 500 million years ago, some of this algae evolved to survive in the intertidal zone: an area between the ocean and land. Slowly, these organisms adapted to conditions further away from the coasts. They diversified into the mosses, which carpet our forest floors. Then came the primordial lycophytes, then ferns, and eventually an explosion of diversity occurred in seed-bearing plants, constituting much of the plant diversity that we know and love today. On our tour, we would get the privilege of encountering organisms from every branch of this phylogeny.

Above: The Green Tree of Life, a composite created by Duke alum Jacob Golan and displayed in the Duke Greenhouses. Courtesy of Katherine Long.

Once we finished our review of the Green Tree of Life, Dr. Manos led our group into a wide room full of tiny plastic pots. With great excitement, he grabbed one and motioned us to take a look. These were Venus fly traps, an infamous carnivorous plant that we learned is native only to the coastal region of North Carolina. With Dr. Manos’ enthusiastic approval, I tapped one of the traps with the tip of my pen and it snapped shut, sadly without the reward of a juicy insect to digest. The room was full of young Venus fly traps, all grown from seed for a research project being conducted on campus. Dr. Manos also pointed out a small collection of pitcher plants, another group of carnivorous plants found in East Coast wetlands and in Australia, Madagascar, and the South Pacific Islands.

Above: Venus fly trap plants housed at the Duke Greenhouses. Courtesy of Katherine Long.

After we had finished marveling at these remarkable plants, Dr. Manos led us into the next room, which housed everything from banana plants to the Instagrammable genus Monstera. He drew our attention to a lycophyte: a member of the small genus of plants that ruled the Carboniferous Era about 350 million years ago. These were the first plants to evolve lignin and vascular systems, which enabled them to grow into the first trees. The remains of ancient lycophytes contributed to the formation of the coal that later fueled the Industrial Revolution. 

Above: Huperzia squarrosa, a member of the lycophyte family, as seen in the Duke Greenhouse. Courtesy of Duke Live Plant Collections.

In this room, we also found a coffee plant, from which we plucked a ripe red pod and split it open to reveal two white coffee beans. These beans are harvested, dried, roasted, and ground up in order to create coffee — and to fuel our late-night study sessions.

In the next room, Dr. Manos showed us a vast collection of ferns. These plants were the first to evolve true leaves (known to scientists as euphylls). The lycophytes might have fooled you, but their leaves are actually discrete extensions of their reproductive tissue! Both genera evolved their versions of leaves in order to increase their photosynthetic surface area. In ferns and their descendants, leaves expanded into wide vascularized structures that could capture even more sunlight.

Slowly making our way through the tightly-packed room, we reached a collection of angiosperms, or flowering plants. Dr. Manos plucked a flower for each of us and challenged us to “diagnose” the anatomy of these structures: to count the number of sepals and petals, to identify the anthers with their pollen, and to split the flower in half to find the ovary with its long style. Flowers have an astonishing diversity in color, shape, size, and symmetry. But one thing they share is a unique geometry: each flower is organized in units. The orchids we diagnosed were organized in threes, cherry blossoms in fives, and bright poppy flowers in fours. 

These extraordinary and beautiful structures constitute the reproductive anatomy of angiosperms. Flowers represent a unique solution to the problem of plants’ sedentary lifestyles. Pollinators like bees, wasps, moths, and bats help transfer pollen to the style, fertilizing the plant and enabling it to produce seeds. Factors like wind, water, and animals help seed-bearing plants distribute their next generation. Flowers also often contain a “reward” of sweet nectar for their pollinators, a taste of which we enjoyed at Dr. Manos’ direction.

The last room we explored held much of the Greenhouse’s gymnosperm collection. Duke students are likely most familiar with gymnosperms in the form of North Carolina’s bristlecone pines. Cones are in fact the common denominator among gymnosperms and represent another solution to the problem of plant sedentarism. Gymnosperms produce “male” pollen-bearing and “female” ovule-bearing cones. Wind helps to spread pollen and fertilize female cones. When a fertilized cone drops, seeds can spread over a wide dispersal area. We found that a huge cloud of pollen erupted from pollen-bearing cones when gently tapped, explaining my seasonal allergies as pollen season kicks into gear.

Above: One conifer species housed in the Greenhouses is Zamia pumila, a type of cycad. Courtesy of Duke Live Plant Collections.

Finally, Dr. Manos led us outside of the Greenhouses. I took a breath of fresh air. Walking through the greenhouse is a sensorially overwhelming experience: there is simply too much to see at once. The branches of arboreal plants hang low over your head, bright flowers pepper the walls, soft leaves brush your ankles and elbows, plants hang from the ceiling, and purple orchids stretch their stems toward you. There are pools of water leaching from freshly watered soil, humid air clogs your lungs, and bright lights shine above you. At every turn, there is some fascinating new organism to marvel at. The very building feels alive. Turning away from the Greenhouses, I was faced with a small meadow of green grasses and clovers and small flowers in shades of white, blue, and yellow. In the Greenhouses, the world was absolutely teeming with life — and, though I wouldn’t have registered it in the hour before our tour, the world outside was too. 

Dr. Manos pointed out the little blue flowers of a weed plant in the meadow outside the Greenhouses and told us they were in one of his favorite plant genera: the genus Veronica. He picked each of us one tiny four-petalled flower and again challenged us to describe it. I smiled as I counted the petals, as I looked for the anthers and style. 1,700 miles away and 15 years ago, I used to be a little girl picking these flowers for my mom on our daily walks.

We picked a dandelion and twisted the top until bright yellow petals began to fall off the stem. Each tuft, Dr. Manos explained, was actually a single flower structure, with a complete reproductive system. There are thousands of flowers on each head of a dandelion. We plucked a gray dandelion from the earth and held it up to the wind, helping it disperse its seeds as Dr. Manos described its life cycle. Like all of us, I used to be a little kid making wishes on these soft gray seeds. 

Above: Between the Greenhouses and the French Family Science Center is a small collection of outdoor plants and a meadow representing the diversity of North Carolina’s herbaceous plant life. Courtesy of Katherine Long.

There is so much to learn within the Greenhouses. They are home to the history of the entire clade of Plantae, to whom we owe our technological advancement, medicine, nourishment, and productivity. Researchers are hard at work unraveling the mysteries of their unique anatomies, metabolisms, and life cycles. Yet, I think the most important lesson to be learned behind those glass walls is one that can only be lived. 

Plants brought color to ancient Earth; they built ecosystems and diversified in form and function. They evolved to produce the huge leaves that we cultivate as houseplants, the bright fruits we enjoy with our friends, and the beautiful flowers we pick for our mothers. Too often, we forget that the trees shading our walk to class and the soft carpet of moss under our feet are alive.

This is the central lesson we can learn by studying plants: life is, and always has been, a shared experience. We evolved in symbiosis with these strange green relatives of ours. Next time you see the gray head of a dandelion, take a minute to pick it and make a wish. Life is all around us, if we only choose to look.

Thanks to Dr. Paul Manos for his phenomenal lessons on plant diversity and his tour of the Greenhouses. Read more about his research here.

To schedule your own tour of the Duke Greenhouses, contact the Greenhouse staff. Check out the Duke Greenhouse Instagram to see some of the plants they cultivate.

Katherine Long

Katherine (Trinity ‘24) is majoring in biology and chemistry with a concentration in cell and molecular biology. She is passionate about scientific communication and research and is excited to contribute to Vertices as a staff writer and peer reviewer. When she’s not in the lab or doing homework, she loves to paint, hike, and hang out with the Duke cat.

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