Winter is Coming…to Minnesota Trees

by Jake Grossman

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Fall colors near Split Rock Lighthouse State Park, MN October 8, 2016
Even though southern Minnesota is hitting peak leaf color right now, University of Minnesota tree lovers were talking about the transition from summer to fall at the Midtown Farmer’s Market on October 1st. Just like us, trees need to prepare for the winter. Unlike the tomato plants in your garden, which die off and can be replanted from seed in the spring, or prairie grasses, which go dormant at or beneath the surface of the soil, trees have have to survive winter with their entire bodies in the freezing air. Some of them even keep their leaves all winter – and supporting all of that living tissue in a cold environment can be a big challenge!

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Jake Grossman, a PhD candidate at the University of Minnesota, explains how trees prepare for and tolerate cold Minnesota winters.

One of the most obvious ways that many trees prepare for winter is by shedding their leaves. During the spring and summer, green leaves, filled with nutrient-rich chlorophyll, make food through photosynthesis. As the days get shorter and colder, trees will suck up as much of the chlorophyll in their leaves as they can. This is a way of recycling nutrients, which can be used next year. The leaves are left without much green pigment, but with plenty of the anthocyanins and carotenoids that produce red, orange, and yellow colors. This is why leaves change color in the fall. The reds and yellows we see in October aren’t new pigments – they were there all along, hiding behind the green. After trees have taken as much out of their leaves, they let them “senesce,” or die off in a controlled way. This is different, and less damaging for the tree, than the freezing damage that you will observe if you leave your houseplants outside during a hard frost.

Minnesota’s trees are preparing for winter on the inside, too! To stay alive, they need to have a constant flow of water running from their roots to their crowns through the long, thin passages called xylem. These structures are like the veins and arteries of the tree, and they function like drinking straws: a bubble or interruption in flow can cause the whole xylem vessel to stop working. If water in the xylem freezes in the winter, it can create air bubbles (air is pushed out of liquid water when it freezes), which disrupt xylem flow. This is called “cavitation,” and must be avoided. Plants have many mechanisms to do so, including, in some species, the creation of natural antifreeze!

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Young scientists examine leaves and leaf litter under the microscope.

At Market Science, we want you to pay attention to how trees prepare for winter. So we asked visitors to become scientists and use a tool that many of us employ in our own research: “litterbags.” Fallen leaves are often called “litter,” so a litterbag is just a mesh bag filled with senesced leaves. Scientists interested in how quickly leaves decompose can put leaves of a known weight in a litterbag, leave them out in the world, and weigh the leaves after some time has passed. The rate of their decomposition can tell us about the leaves’ chemical composition and the environment where they were decomposing. Our visitors got to do this, too, by making litterbags filled with leaves from oak, pine, eastern red cedar, box elder, and basswood! These newly trained litter scientists will place their bags around their homes and yards and check them periodically to see how decomposition proceeds for their leaves of choice.

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Litterbag supplies: old leaves and empty mesh bags.

Thanks to everyone who came out to learn about the ways that MN trees prepare for winter. Two pieces of news for those who visited us:treefoliage

1. In case you were wondering, maples were the runaway favorite in our poll of favorite fall foliage, beating out birches, aspens, and oaks.

2. If you brought home a litterbag, keep an eye on it as we move through winter and spring. If you take a picture of it decomposing next year and send it to Market Science, you’ll be entered in a drawing to win a tote bag. Get in touch here.

Wild About Wheat (and Other Grains)!

by Drs. Katie Liberatore and Marisa Miller

Did you know that Aegilops – the name for a genus of grasses including wild wheat relatives – is the longest word in the English language in which the letters are arranged in alphabetical order? This was just one of the many fun facts shared by volunteer scientists and educators at the Market Science booth this past Saturday at the Midtown Farmer’s Market.

We talked a lot about domestication of cereal crops this week, particularly wheat and barley. Humans began the process of cultivating these plants for use in the fertile crescent around 10,000 years ago. Some were interested to find that barley had a second point of domestication in western Asia. Modern cultivated wheat and wild species were on display to give an in-person view of how plants have been adapted to modern agriculture practices by humans. We discussed how the ancestors to both plants used to have “shattering” seeds that readily fell off the plant – this was important to spread the seeds in the wild. However, people selected for “non-shattering” plants so that all of the grains stay put until ready for harvest all at once. Market-goers were able to look under the microscope to view “shattering” versus “non-shattering” seeds, which have smooth and rough break-points from the plant, respectively.

Market-goers were able to test their knowledge of where in the world cereal grains, pseudocereals, and and grain legumes were domesticated with a fun matching game. Those who were paying attention in the first lesson were able to place wheat and barley on the map right away. Some crops were much more difficult to match to their point of origin – most were surprised that peanuts were first cultivated in the Andean region of South America!

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What defines a cereal versus a pseudocereal versus a grain legume? Good question! True cereals all belong to the grass family (Poaceae). True cereals include wheat, barley, oat, rye, corn, rice, sorghum, millet, and teff. Pseudocereals are not grasses, but are used for nutritional purposes like cereal grains. These include buckwheat and quinoa. Grain legumes are subset of legume crops that are grown for consumption of their seeds. These include peanuts, soybean, and chickpea.

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Budding artists had fun trying their hands at seed art. For the more scientific of the bunch, matching the grains to the proper plant was fun, while others chose to decorate farm scenes. Some market-goers even honored Prince with Purple gRAIN art. It was a great day at the Market! We hope to see you next Saturday.

Skippers and Crescents and Blues, Oh My!

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This week at the Market, we talked all about butterflies and the many types of butterflies that you can find in Minnesota. Did you know that there are about 146 species of butterflies in Minnesota and the most of them survive the winter here just like us! Market-goers were able to meet some of these Minnesota natives butterflies and try to identify them. We had Pearl crescents, Cabbage whites, and Eastern tailed blues.

We also talked a lot about how butterflies make different patterns on their wings. Did you know that they are actually made from lots of tiny overlapping scales on the butterflies’ wings. In fact, the other name for butterflies and moths collectively is “Lepidoptera”, which means “scaly wings”.

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We then talked about why butterflies have different wing patterns: to scare predators, to hide from predators, or to tell predators that they don’t taste good. Then junior market scientists were invited to color their own butterfly wings and there were a lot of great creative patterns!

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We also talked about how butterflies have a very specific life-cycle. They start as eggs, hatch and grow as caterpillars, turn into a pupae in a chrysalis, and then emerge as the adult butterflies that we all see. Market-goers could play a guessing game to match the caterpillar with its adult and junior market scientists could make their own caterpillars to match the butterfly that they drew.

Lastly, Market-goers could learn about the very special butterflies in Minnesota that are currently at risk, like the highly endangered Poweshiek skipperling. Did you know that 15 species of butterflies are listed as Endangered, Threatened, or Special Concern by the State of Minnesota? Ten of these species depend on our disappearing native prairies. These Minnesotans are facing many challenges due to loss of habitat and other potential problems. We also learned about what places like the Minnesota Zoo and Monarch Joint Venture are doing to try and save these animals and ways that we all help butterfly populations in Minnesota!

Bioreactors!

On July 30, researchers from the Ishii laboratory at the University of Minnesota came out to the Market to demonstrate an innovative method for removing nitrogen pollution from water: woodchip bioreactors.

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When nitrates build up in our local waters, algae blooms can develop which alter the water chemistry and make it difficult for many other animals and plants to thrive. Agriculture often needs to use nitrate-based fertilizer to grow crops, so researchers have worked to find ways to remove this nitrate from water draining off fields. Woodchip bioreactors are a sustainable method to remove up to 50% of the potential nitrate pollution!

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A demonstration of a woodchip bioreactor: the nitrate-loaded water would drain into the woodchips full of nitrate-breathing bacteria; they would breathe out NO2 (nitrogen gas) and leave the remaining water less polluted. In a field, the woodchips are all buried!

 

The woodchips act as a home and food for many small bacteria (tiny organisms or microbes). As we need oxygen to breathe, the microbes use the potentially polluting nitrate and breathe out (respire) nitrogen gas (NO2), which isn’t a pollutant. Then the water can run-off to nearby streams and eventually lakes with far less nitrate!

The systems are constantly being improved. The Ishii lab studies the microbes to try and select bacterial types that are more efficient at removing nitrates. Other researchers study the best ways to move water through the systems. Many farms in Minnesota and elsewhere already have woodchip bioreactors in their fields.

Thanks to the microbiologists of the Ishii Lab!

Dynamic Earth at the Market

by Kevin Theissen

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Our planet is a dynamic, ever-changing system and this past Saturday at the market we explored the fascinating science of geology with a team of students and faculty from the University of St. Thomas.   Geologists use physical models to understand the natural behavior of streams like our local Mississippi River. The models provide insight on major processes such as erosion, transport, and deposition–and the sometimes hazardous consequences which include flooding and landslides. Visitors got hands-on experience investigating the interactions between water flow and landscape with a table-top stream table. They created hills, dams, slopes, and stream channels and experimented with changes in the rate of streamflow. Visitors learned that the “sediment” for our stream table was an unexpected material—recycled toilet seats!

 

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The Earth’s large crustal plates move at the rate that our fingernails grow and accordingly lead to much slower changes than rivers. Given hundreds of millions of years, however, those slow changes mean dramatic differences.   Visitors observed marine fossils of organisms known as brachiopods, bryozoans, and crinoids representing a shallow tropical sea that once covered the Twin Cities and much of southeastern Minnesota during a period of geologic time known as the Ordivician, more than 450 million years ago. Reconstructions of plate movements suggest that Minnesota was likely centered on the equator during this time.

 

Visitors also donned 3-D glasses to get dramatic views of a variety of important plate tectonic settings where plates converge, spread apart, and slide past each other.   Perhaps the best example of this is the Pacific ‘Ring of Fire’ which includes deep-sea trenches, mid-ocean ridges, and several large mountain chains.

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Junior scientists topped all of this off by decorating their own pet rocks!

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Red Leaf, Green Leaf: Exploring Plant Pigments

By Laura Nelson

Do you know why leaves change colors in the fall? The answer has to do with chemical compounds in leaves known as pigments. You may have heard of the green pigment chlorophyll. At the Nokomis Market on July 27, visitors explored how other pigments are present in leaves all the time but are invisible until autumn. Seasonal changes, including shorter daylight hours, cause plants to break down chlorophyll which is quite “expensive” in the amount of energy needed to produce it. Visitors explored the importance of chlorophyll in photosynthesis by recreating the photosynthetic cycle on a felt board. When photosynthesis slows in the fall and a plant breaks down chlorophyll into its components, it will recycle these component nutrients. Other pigments that were once hidden become visible because of the breakdown of chlorophyll. The pigments xanthophyll (yellows and browns), carotenoids (orange), and anthocyanins (reds and purples) are the vibrant colors we see showing through in autumn.

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To explore the idea hidden pigments, market goers performed chromatography, the process of separating a substance into its components. Visitors separated colors by marking a dot on a piece of chromatography paper, dipping it in water, and observing the water soak up the paper through capillary action. The results showed that secondary colors like green separated into primary colors like blue and yellow. You can perform your own chromatography with markers at home using coffee filters.

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Separating leaf pigments takes up to an hour, so market goers prepared their own take-home leaf chromatography kits. Market Scientists provided leaf samples from a common houseplant called Zebrina with bright purple and green leaves. Visitors tore the leaves into small sections, put them in a plastic vial, and covered the leaf bits with a small amount of isopropyl alcohol. Equipped with their own leaf samples, chromatography paper, and instructions, market goers left with science kits to explore leaf pigments. Curious about the results? Take a look at the chromatography paper below. Can you pick out the two primary pigments anthocyanin and chlorophyll?

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Visitors separated colors with a prism, but instead of pigments, they saw different wavelengths in the visible light spectrum. Our youngest visitors also enjoyed observing leaf trichomes, or hairs, under a microscope. Thank you to Nokomis Market for welcoming the Market Scientists and for all the visitors who explored leaf colors with us!

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Pollen and Plant Development

By Claire Milsted

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Almost all of our food comes directly or indirectly from flowering plants (angiosperms); many plants without conspicuous flowers, such as corn, fall into this category. Angiosperms release specialized cells known as pollen to carry half of their genetic information to other plants for reproduction (though many angiosperms also pollinate themselves). This Saturday’s Market Science session at Midtown Farmer’s Market focused on pollen and plant development. Even though the farmer’s market was unexpectedly rained out before 11am, many visitors were able to participate in one or more activities designed to trace plant development from a flower to pollen to seed.

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A bumblebee visits a rhododendron in Saint Paul. Bumblebees are important pollinators.

In many species, this pollen must be carried by animal pollinators. About 35% of the global food supply comes from plants that require animal pollinators. Our first activity was a guessing game that asked visitors to guess how various flowering plants are pollinated. Most visitors knew about the importance of bees, but some were surprised to learn about other important vectors of pollination. For example, corn is wind-pollinated, while the Blue Agave Cactus is pollinated by the Mexican Long-nosed Bat.

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A Mexican long-nosed bat prepares to pollinate a Blue Agave Cactus. Image via nwf.org

Visitors were also offered the chance to examine various flowers both with the naked eye and with a dissection microscope. Visitors examined lilies and tomatoes, which have simple flowers with several pollen-containing anthers surrounding a pollen-receiving stigma. There were also compound flowers, with a single flower-head made of several small flowers. The compound flowers on display were chrysanthemums, the invasive species Queen Anne’s Lace, and daisies. Daisies are members of the Asteraceae family, which have flower heads that look like a single flower surrounded by petals, in fact each of the small bumps on the head are an individual disk flowers; the structures that look like petals are in fact ray flowers.

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A member of the Asteraceae grows in Saint Paul

Visitors were also able to look at pollen from daylilies and tomatoes under a compound microscope. Daylily pollen was much larger and had a different shape. Finally, visitors were invited to dissect soaked beans and examine them under a dissection microscope. Volunteers explained the various components of a bean seed–its protective coat, two cotyledons which store energy for the growing plant, and a small embryo with two visible embryonic leaves (epicotyls). Hopefully these activities exploring flowers, pollinators, pollen, and seeds gave visitors a clearer view of the developmental and reproductive processes that play an important role in our gardens and on our farms.

 

Healthy Prairies

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Have you ever seen a Minnesota prairie? If you have, you’re lucky! It is such a unique and fascinating ecosystem, but is disappearing at an alarming rate. Minnesota had over 18 million acres of prairie in the late 1800’s, and now only 1% of that remains.

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A few scenes from a Minnesota prairie

The Healthy Prairies Project is a UMN research initiative funded by MN LCCMR to help conserve and restore our native prairies.  On Saturday, visitors at the Midtown Farmers Market got to meet the Healthy Prairies team and learn about this precious MN ecosystem! They even got to make their own “seed balls” filled with native perennial grass seeds, which they can take home to grow their own prairie plants.

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Making seed balls filled with native MN perennial grass seeds

Perennial prairie grasses like Big Bluestem (Andropogon gerardii) and Sideoats Grama (Bouteloua curtipendula) have very deep roots that help reduce soil erosion, filter water, and store lots of carbon. Plus, they’re extremely drought tolerant!

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You can compare the roots of regular turfgrass (far left) and native plants to see that natives have a lot more going on underground!

There are also a whole host of prairie wildflowers that serve as important food sources for lots of pollinators like bees and moths. You can learn more about planting a prairie garden here.

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A small bumblebee seeking out nectar and pollen from Purple Coneflower (Echinacea purpurea), a MN native wildflower

But did you know there’s even cool stuff going on inside the leaves of these plants? Every leaf of every plant you see has fungi and bacteria living inside; we call these microbial dwellers leaf endophytes. At the Healthy Prairies Market Science session visitors got to see the huge diversity of fungi that live inside the leaves of some prairie plants.

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These Petri dishes are growing fungi collected from leaves of Purple Prairie Clover (Dalea purpurea)

As UMN graduate student Mara DeMers explains,

If plants are filled with fungi and bacteria, just what are those microorganisms doing in there? In fact, different endophytes do different things, and there are MANY different fungi and bacteria that live as endophytes. So the short answer is: Lots of things!

What’s the long answer? Some endophytes can protect their plant hosts from being eaten, or help them survive in hot or dry places. Others might actually be pathogens, but are living as endophytes because some condition isn’t right for them to cause disease. For many endophytes, we still don’t have an answer. Maybe they help the plant, or maybe they hurt the plant, or maybe they don’t affect the plant at all. We don’t know yet!

Plant endophytes are a rapidly developing field in biology, and the Healthy Prairies team is on the forefront of research investigating the roles these microbes play in the prairie.

We hope you enjoyed visiting the Healthy Prairies team at Midtown, and that you’ve thrown your seed balls far and wide! There are lots of prairies you can visit across the state; here are a few to get you started.

Ethnobotany: Using plants for food and medicine

By Stephanie Erlandson

This Saturday (July 9) we got to strengthen our connection to plants by examining more closely what we eat, and how some common plants can be used for medicine.

We eat plants all the time, but we rarely take a closer look at what’s inside.  By dissecting plants, we can look at their seeds, their ovaries (yes, plants have ovaries!) and figure out if a specific plant part is a fruit, a leaf, a stem, or a root.  We can also learn more about how plants are related to each other.  For example, the African horned melon (kiwano) is actually closely related to the pumpkins, squash, and watermelons that are more common here in Minnesota.

There were a variety of plants available for dissection, and a map showing the origins of many different agricultural plants from around the world.  Many of the plants that we rely on for food are actually not native to Minnesota (e.g. wheat, oats, watermelon, peas, almonds, coffee).

Visitors were also asked to vote for their favorite berry, and many were shocked to learn that cucumbers are a type of berry, but raspberries and strawberries are not! After voting, visitors learned that a true berry is a fruit that is fleshy, has many seeds on the inside, and grows from only one ovary on a single flower.

Finally, we had some examples of medicinal plants (ephedra, spearmint, horsetail, ginkgo) to view, and we talked about which medicines they provide.  For example, pseudoephed came from the ephedra plant and aspirin came from willow bark.  Willow bark contains salicylic acid, which is a precursor to aspirin.  What plants did the medicines in your cabinet come from?

There are many more medicinal plants around the world that are still unknown to science, and the process of discovering them is still ongoing.  For example, a new chemical was recently extracted from the sweet wormwood plant, and it was found to be very effective at treating malaria.  The scientist to discover the drug, Tu Youyou, was awarded the Nobel Prize in 2015.

Hopefully this market science day will help encourage people to take a closer look at the plants around them, and appreciate everything that they do for us!

Genes, Genomes, and GMOs

By Diana Trujillo

On June 25, we had a session about the code underlying all living things: DNA! The purpose of the Genes, Genomes, and GMOs session was to demystify DNA and genetics for market goers.

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Using commonly available items such as coffee filters, soap, salt and rubbing alcohol, kids and adults alike had great fun extracting DNA from strawberries. We learned that the “stringy white stuff”, aka DNA, contains genes, which determine strawberries’ shape, color, taste, and growth habit!

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That string is an accumulation of DNA extracted from a strawberry!

In order to look at DNA more in depth, another activity was DNA origami. We put our folding skills to the test, creating a spiral staircase that depicts the double helix structure of DNA. These two anti-parallel strands contain complementary information which allows the sequence to reliably be copied and passed down from one generation to the next. Want to recreate the human genome using DNA origami? Great, only 3 billion more to go!

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A very small section of DNA. We have over 3 billion base-pairs (the single letters connected to one another across the helix) in our human DNA!

For those wondering how it all comes together, we used a poster to show that DNA strands are coiled many times in order to be packaged into cells, and that the collection of all the genetic information in one cell constitutes a genome. The genes within a genome have natural variations among individuals, such as tall vs. small plants or red vs. yellow fruits. For thousands of years, humans have unknowingly selected the very best gene variants during the course of a crop’s domestication.

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Newer technologies allow us to make targeted changes to genomes, such as the disruption of a gene, or introduction of new genes. The result? Genetically modified organisms, or GMOs. In one final activity, Erik showed us which produce items currently on the market are genetically modified, and explained which ones will be available in coming months.

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Erik Solhaug, a University of Minnesota graduate student, shows off a mix of crops in a GMO guessing game.