#60secondscience – Page 2 – My Chicago Botanic Garden

60-Second Science: Phylogenetic Trees

Dr. Evelyn Williams is an adjunct conservation scientist at the Garden. She’s interested in genetic diversity at multiple scales, from the population to the family level. While at the Garden, Dr. Williams has worked on rare shrubs from New Mexico (Lepidospartum burgessii), systematics of the breadfruit family (Artocarpus), and using phylogenetic diversity to improve tallgrass prairie restorations.

When a scientist says that chimpanzees are related to humans, or that chickens are related to dinosaurs, what do they mean?

They mean that chimpanzees and humans share a common ancestor from many thousands of generations ago. Although that shared great-great-great-great-(etc.)-great-parent lived many years ago, that shared ancestor lived more recently than the ancestor that humans share with dogs. So humans are more closely related to chimpanzees than dogs because they have the most recently shared ancestor. Scientists call this the “most recent common ancestor.”

This most recent common ancestor wasn’t a chimp, and it wasn’t a human—it was a different species with its own appearance, habits, and populations. One of these populations evolved into humans, and one of the populations evolved into chimpanzees. We know this because of a field of study called “phylogenetics.” Scientists use phylogenetics to study how species are related to each other.

Using DNA sequences, scientists construct tree-like diagrams that trace how species are related. A human’s DNA is more similar to a chimpanzees’ than to a chicken, so a tree diagram would connect humans and apes. Dinosaurs and chickens would be shown as related as well, and then these two groups would be connected.

Interested in learning more? Explore phylogenetics with the Tree of Life Web Project. Dig deep into the study of the phylogenetic roots of food plants with The Botanist in the Kitchen.

Students in the Chicago Botanic Garden and Northwestern University Program in Plant Biology and Conservation were given a challenge: Write a short, clear explanation of a scientific concept that can be easily understood by non-scientists. This is our fourth installment of their exploration.

60-Second Science: Prairies Need Fire

Becky Barak is a Ph.D. candidate in Plant Biology and Conservation at the Chicago Botanic Garden and Northwestern University. She studies plant biodiversity in restored prairies, and tweets about ecology, prairies, and her favorite plants at @BeckSamBar.

A dark, stinky plume of smoke rising from a nature preserve might be alarming. But fire is what makes a prairie a prairie.

A prairie is a type of natural habitat, like a forest, but forests are dominated by trees, and prairies by grasses. If you’re used to the neatly trimmed grass of a soccer field, you may not even recognize the grasses of the prairie. They can get so tall a person can get lost.

Prairies are maintained by fire; without it, they would turn into forests. Any chunky acorn or winged maple seed dropping into a prairie could grow into a giant tree, but they generally don’t because prairies are burned every few years. In fact, fossilized pollen and charcoal remains from ancient sediments show that fire, started by lightning and/or people, has maintained the prairies of Illinois for at least 10,000 years. Today, restoration managers (with back up from the local fire department), are the ones protecting the prairie by setting it aflame.

PHOTO: Chicago Botanic Garden ecologist Joah O'Shaughnessy monitors a prairie burn. — Garden ecologist Joan O’Shaughnessy monitors a spring burn of the Dixon Prairie.

PHOTO: New growth after a prairie burn. — New growth emerges a scant month after the prairie burn.

Prairie plants survive these periodic fires because they have incredibly deep roots. These roots send up new shoots after fire chars the old ones. Burning also promotes seed germination of some tough-seeded species, and helps keep weeds at bay by giving all plants a fresh start.

Read more about our conservation and restoration projects on the Chicago Botanic Garden website. Want to get involved in our local ecosystem conservation? Find your opportunity with Chicago Wilderness.

60-Second Science: Plants’ Roots Helped Them Move to Land

Alicia Foxx is a second-year Ph.D., student in the joint program in Plant Biology and Conservation between Northwestern University and the Chicago Botanic Garden. Her research focuses on restoration of native plants in the Colorado Plateau, where invasive plants are present. Specifically, she studies how we can understand the root traits of these native plants, how those traits impact competition, and whether plant neighbors can remain together in the plant community at hand.

Life for plants on land is hard because the environment can become dry. Water is important because it is used when plants take in sunlight and carbon dioxide to make energy; this is called photosynthesis. In fact, the largest object in a plant cell is a sack that holds water. Without water, plants would die.

Plants first evolved in water, which is a comfortable place: there is little friction, you almost feel weightless, and…there was plenty of water back then. These plants had no difficulty photosynthesizing, as water diffused quite easily into their leaf cells! They had little use for roots.

Evolving Plant Structures

In the time plants evolved to live on land (100 million years later), water shortages and the need to be anchored in place became issues and restricted plants to living near bodies of water. Some plants evolved root-like structures that were mostly for anchoring a plant in place, but also took in some water.

It wasn’t until an additional 50 million years after the move on to land that true roots evolved, and these are very effective at getting the resources essential for photosynthesis and survival. In fact, the evolution of true roots 400 million years ago is associated with the worldwide reductions in carbon dioxide, since more resources could be gathered by roots for photosynthesis. Importantly, plants were no longer tied to bodies of water!

PHOTO: tree roots. — Large roots anchor a plant in place.

PHOTO: bulb with tiny bulblets and root hairs. — Tiny root hairs on a bulb take up nutrients when moisture is present.

Water issues continued, however, even with true roots. Early roots were very thick and could not efficiently search through the soil for resources. So plants either evolved thinner roots, or formed beneficial associations with very tiny fungi (called mycorrhizal fungi) that live in the soil. These fungi create very thin, root-like structures that allow for more effective resource uptake. In general, while life on land is hard, plants have evolved ways to cope via their roots.

Garden scientists are studying the relationships between plants and mycorrhizal fungi in the soil. Orchids are masters of nutrient collection. The vanilla orchid has terrestrial (in soil) and epiphytic (above ground, or air) roots—and forms relationships with fungi for nutrient collection. Read more about research on Vanilla planifolia here.

60-Second Science: Dormancy and Germination

Students in the Chicago Botanic Garden and Northwestern University Program in Plant Biology and Conservation were given a challenge: Write a short, clear explanation of a scientific concept that can be easily understood by non-scientists. Each week this spring, we’ll publish some of the results.

These brief explanations cover the topics of seed dormancy and germination, the role of fire in maintaining prairies, the evolution of roots, the Janzen-Connell model of tropical forest diversity, and more. Join us the next several weeks to see how our students met this challenge, and learn a bit of plant science too.

Alexandra Seglias is a second-year master’s student in the Plant Biology and Conservation program at Northwestern University/The Chicago Botanic Garden. Her research focuses on the relationship between climate and dormancy and germination of Colorado Plateau native forb species. She hopes that the results of her research will help inform seed sourcing decisions in restoration projects.

PHOTO: A tiny oak sprouting from an acorn. — A tiny oak emerges from an acorn. Photo by Amphis (Own work) [CC BY-SA 3.0], via Wikimedia Commons

Dormancy and Germination

The seed is an essential life stage of a plant. Without seeds, flowers and trees would not exist. However, a seed doesn’t always live a nice, cozy life in the soil, and go on to produce a mature, healthy plant. Similar to Goldilocks, the conditions for growth of a seed should be “just right.” The charismatic acorn is just one type of seed, but it can be used here as an example. Mature acorns fall from the branches of a majestic oak and land on the ground below the mother tree. A thrifty squirrel may harvest one of these acorns and stash it away for safekeeping to eat as a snack at a later time. The squirrel, scatterbrained as he is, forgets many of his secret hiding places for his nuts, and the acorn has a chance at life. But it’s not quite smooth sailing from here for that little acorn.

Imagine trying to be your most productive in extreme drought, or during a blizzard. It would be impossible! Just as we have trouble in such inhospitable conditions, a seed also finds difficulty in remaining active, and as a result, it essentially goes into hibernation until conditions for growth are more suitable. Think of a bear going into hibernation as a way to explore seed dormancy. The acorn cozies up in the soil similar to the way a bear crawls into her den in the snowy winter and goes to sleep until spring comes along. As the snow melts, the bear stretches out her sore limbs and makes her way out into the bright world. The acorn feels just as good when that warmer weather comes about, and it too stretches. But rather than limbs, it stretches its fragile root out into the soil and begins the process of germination. This process allows the seed to develop into a tiny seedling — and perhaps eventually grow into a beautiful, magnificent oak tree.

Our scientists are studying seed germination in a changing climate. Learn how you can help efforts to help match plants to a changing ecosystem with the National Seed Strategy.