Plants have a plan for all seasons

Many plants need to avoid flowering in the autumn – even if conditions are favourable – otherwise they would perish in winter.

To flower in the spring they need to sense and then remember winter, a process known as vernalisation. But how do plants sense vital information such as temperatures to align flowering with the seasons?

Until now, many researchers thought that fluctuations in monthly, daily, hourly temperatures were detected by a small number of dedicated sensors.

But new research by the John Innes Centre reveals that plants combine the temperature sensitivity of multiple processes to distinguish between the seasons.

"At first glance this might seem like a surprising finding, however in hindsight, it is very reasonable and it is also more likely as a mechanism to evolve," comments Dr. Rea Antoniou-Kourounioti, first author of the study which appears in the journal Cell Systems.

"Biochemical reactions are naturally temperature sensitive, so the alternative, a few specialised sensors, would suggest that the temperature sensitivity of everything else must be ignored or compensated for. On the other hand, taking inputs from multiple pathways that were already responding to temperature, and evolving to use this combined information is less complicated and can lead to a more robust system," she explains.

The team from the labs of Professors Martin Howard and Caroline Dean developed a predictive mathematical model of temperature sensing for the key flowering regulator FLC in Arabidopsis.

This vernalisation model can be used in combination with climate models to predict how plants will change their flowering in future climates. In this study, the team collaborated with groups from Sweden to test the model on patterns of data from plants grown in field sites in Sweden and Norwich – and the model matched these well.

Arabidopsis is a relative of many crop species, such as broccoli and oilseed rape, so the work could be extended to help breeders develop climate-resilient varieties.

Future work will involve adjusting the model in crop species and integrating it into current crop prediction models for farmers and breeders.

The team will work with climate modellers to more accurately predict the temperatures that plants will actually experience in future.

Grant will help determine how plants interact with microbiomes

While many people know that the microbes in our guts are an important part of our health, many are unaware that microbes are just as important to our crops.

Different microbes can help plants acquire nutrients, fend off pests and disease, and produce higher yields, but we know very little about how these partnerships work. University of Georgia researchers are working to understand these partnerships so that they can be used to breed better, more sustainable crops.

A team of researchers at the University of Georgia College of Agricultural and Environmental Sciences has received a $1.35 million grant from the National Science Foundation to better understand how plants interact with their microbiomes.

"Just like people, plants host trillions of microbes that live on, around and inside them," said principal investigator Jason Wallace, a CAES professor of crop and soil sciences. "Some of these cause disease but many are beneficial, helping the plant thrive in harsh conditions, but we don't know how this interaction works.

"Learning how a plant's microbes make it more resilient could be an important key to developing more sustainable and stress-tolerant crops in the future."

Wallace's team is focusing on a grass called tall fescue, which has been grown for animal feed for over 70 years and covers 40 million acres across the U.S.

While breeding more water-efficient fescue has been a goal of plant breeders for decades, UGA geneticists are taking a new approach. They are investigating how the grass interacts with symbiotic fungi, which has been found to fortify it against heat and drought stress.

Some types of tall fescue have a fungus, Epichlo coenophiala, living inside them, which helps the plant survive drought, heat and disease. It also helps the grass fend off insects and predators.

Ironically, this partnership was discovered because the fungus usually produces toxic chemicals, ergot alkaloids, that make cattle sick. UGA was instrumental in breeding the first commercial varieties with toxin-free strains back in the 1990s.

Wallace's team will work with fescue that contains the fungus to understand how such a beneficial partnership works, including how the plant and fungus communicate with each other and how their interaction leads to higher stress tolerance in the plant.

The hope is that understanding this system will show how similarly strong, beneficial partnerships can be made in other crops to boost agricultural production and sustainability.

Wallace is partnering with Carolyn Young, an associate professor at the Noble Research Institute in Ardmore, Okla., to carry out this research.

To complete this work, Wallace, Young and their research teams will analyze thousands of fescue plants to find how the plant influences fungal growth and toxin production. They will also investigate how the plant forms relationships with new varieties of fungus, such as ones that do not produce toxins, and how the fungus helps the plant survive under heat stress that would normally kill it.

In addition to the work with fescue, Wallace and Young will assist middle and high school teachers in developing hands-on teaching projects related to these topics that they can implement in their own classrooms. This will give students a better understanding of plant-microbe partnerships and the ways that microbes impact the larger ecosystem.

The grant period will run from 2019 through 2022, but some parts of the project are already underway.

These plants bring all the birds to your yard

Like songbirds? Right, many people do. It's a different story when it comes to insects. Mention caterpillars, for instance, to most gardeners, and you'll have them squirming with horror. But backyard species like caterpillars and spiders actually play a crucial role in supporting our most beloved bird species. As a new study from University of Delaware postgraduate student Desirée Narango and coauthors demonstrates, native plant gardens are quite literally for the birds.

It's the largest comprehensive study to date of the effect of native plant species on a specific species of bird—the Carolina chickadee. It's also the biggest single piece of research to come out of years of fieldwork during Narango's PhD, she says, and it offers a tangible goal for conservation-minded individuals to work for in their own yard. That goal is a number: 70 percent.

By studying more than 160 yards, Narango found that suburban lawns with at least 70% native trees and shrubs were able to sustain breeding chickadees. Yards with less could sustain adults, but those adults weren't reproducing at replacement rate, meaning the population was falling.

Why are native plants important? When it comes to birds, it's because those plants have coevolved with local insect species—creepy crawlers that the birds themselves evolved to thrive on, says University of Maryland ecologist Karin Burghardt. Burghardt previously worked with Narango's coauthor, University of Delaware professor Doug Tallamy, but she was not involved with the current study.

"We think about birds [in human landscapes] as mostly needing birdseed," Burghardt says. But work over the past decade paints a different picture, one that points to the importance of insects for many. However, the vast majority of plant-eating insects are evolved to only eat a small number of native plants, which means that in gardens without the foliage of choice, they're not around.

For human gardeners, as well, introducing native plants and seeing the wildlife—from caterpillars and other insects to birds—they attract can be "a pretty rewarding process," Burghardt says. She recently bought a house, where she's in the process of redoing the garden with native species. Gardeners who do the same will quickly see results, she says, and know that they are providing homes for wildlife, from the crawly to the flappy.

Narango says that the 70 percent number that works for the chickadee is a baseline. "Almost all terrestrial songbirds require insects to raise their young," she says. The more insectivorous a bird, the higher percentage of native plants it seems to need for those insects to live on. The Washington, DC backyards she monitored were part of an existing citizen science project called Neighborhood Nestwatch.

Doing fieldwork is often no simple task, particularly in urban areas, says Tallamy. He's been working on the problem of backyards for more than a decade—Burghardt was his coauthor on some of the work that originally demonstrated the relationship between native plants and insects. Tracking hundreds of yards and birds "is not easy stuff," he says.

In this case, each participating yard got a nestbox, and homeowners monitored the box from the first week of April through June to see if chickadees moved in for their breeding season. Narango and her field technicians also visited the yards of neighboring houses to see if chickadees that were feeding in the backyards they studied were actually nesting close by but not in the yard itself.

Their results show something that hasn't been seen before: a comprehensive study of the effect of non-native species of plants, higher up the food chain, Tallamy says. It takes a story he's been working on for a long time and stretches it "to the next trophic level," he says, by looking at the birds who eat the insects.

"These simple choices on what people are planting can really have profound consequences on the birds that are living in these yards," Narango says. Those consequences stretch beyond nesting birds and to the migratory birds that pass through on their long journey from the tropics to Canada's boreal forests each year. They might only stop in a yard for a week, but they're looking for high-calorie, high-protein food to sustain their next great hop—just like the nesting birds that need extra to raise young. If they can't find food on their stop, that week "could be the most important week of their life."

The new study does a "meticulous" job of defining what insects can do for birds, says Burghardt, but it's important to remember they're more than just food. "I think that they have value in and of themselves," she says. They're part of a web of life evolved long before we started bringing non-native plants to our gardens. They also have the potential to enrich gardens, says Nancy Vehrs, president of the Virginia Native Plant Society. "There's more to a garden than just the plants," she says.

Successfully transplanting landscape plants takes forethought, preparation

McDONOUGH — If you want to rearrange your landscaping, the best time to do so is quickly approaching, though it's not easy lifting.

Nurseries use tree spades to dig large trees from a field-grown nursery. Unfortunately, this is not the kind of equipment a home landscaper can rent for a weekend project.

The roots of trees and shrubs normally grow beyond the amount of soil a home gardener can move. To keep most of the roots within a small area, plants should be root-pruned in the spring or fall before transplanting. Root pruning is the process of severing the roots of an established plant that is going to be transplanted to encourage growth of new feeder roots along the root ball.

Plants moved in the fall (October or November) should be root-pruned in March. Those moved in spring (March) should be root-pruned in October. Root-prune after the leaves have fallen from deciduous plants in the fall or before buds break in the spring.

To root-prune, mark a circle the size of the desired ball around the tree or shrub. Next, dig a trench just outside the circle. Cleanly cut larger roots and backfill the trench with the available soil. Water the area to settle disturbed soil and provide adequate moisture.

Roots within the pruned area grow many new fibrous roots, and form a strong root system within a confined area. If not root-pruned, larger plants may die from transplant shock because of root loss.

Shrubs less than 3 feet tall and deciduous trees less than an inch in trunk diameter (measured 6 inches above the ground) may be moved bare root. "Bare root" means most or all of the soil is removed from the roots.

Bare-root plants are easier to handle than those with a ball of soil around the roots. Bare-root plants should be planted while dormant. It is best to immediately replant. If not, keep the roots moist in peat moss or wrapped in plastic or wet papers until you are ready to plant.

To move trees with soil attached to the roots, trim the root ball to the proper size and shape with a spade. Keep the back side of the spade toward the plant, round off the trimmed ball at the top and taper it inward toward the base.

Avoid loosening the soil around the roots by cutting the large roots with hand or lopping shears and the small roots with a sharp spade. Next, undercut at an angle of about 45 degrees to loosen the root ball from the soil and sever remaining roots.

Prepare the new site before transplanting a tree or shrub. Have the soil tested and follow recommendations. Don't use fertilizer that contains nitrogen for the first year after transplanting.

Dig the new hole 50 percent wider than the soil ball to loosen the surrounding soil and ensure good root establishment. The root system should be at the same depth it was before it was moved.

Research has shown that adding soil amendments to the planting hole will not provide any benefits to newly planted trees or shrubs. Most studies show amendments can create drainage issues and cause poor root establishment.

When moving the plant to its new home, lift trees and shrubs by the root ball. Never carry a tree by the stem. This can damage underlying bark tissues. Place the plant in the hole and backfill with existing native soil.

Maintain constant moisture, not saturation, of the root ball. Add 2 to 3 inches of mulch to help conserve moisture, moderate temperature extremes and reduce weeds. Keep mulch away from the trunk of the plant.

Allan Armitage: Let's Tell Our Story About Pollinator-Friendly Plants

In the last 10 years, we have become more aware of the role pollinators and pollinator plants play in the world's ecosystem. We have come to understand that bees, butterflies, ants, and beetles contribute significantly to the global economy and food supply. We also know bees and butterflies are attracted to some plants more than other ones and that pollinator-friendly plants are important.

Of the great issues facing the ecosystems of our planet, there are not many that horticulturists and our industry can directly affect in a big way. The Amazon rainforest, the warming of planet Earth, and other issues all affect us, but there is little a gardener/horticulturist can do. However, let it not be said that we should not be involved in trying to maintain ecological balances at the local level. We brought out the marketing gloves, and we are now in the middle of the fight to reduce invasive plants, increase native flora, and promote pollinators. Profit motive aside, I sometimes feel we should all be wearing halos.

How Real is Real?

Of course, the profit motive doesn't hurt any. We have been told that the native plant and the pollinator movements are real. We have responded by breeding more native plants, whose very definition (rightly or not) is that they attract pollinators better than non-natives do.

However, I am not sure what real means. For me, the realness test is if my neighbors and daughters are behind it. As I wander through the gardens of America, I wonder if the gardeners are thinking about natives/pollinators when they walk through the box store or garden center? Do they ask if the plants in their carts are good for pollinators? If they are not, why not? Or, are they aware of anything other than that the plants are pretty?

Are consumers catching up to our marketing messages, or do we have a ton more to do to be sure they are listening? Gardening concepts are always evolving, this being one of them. The issue of pollinators and pollinator-friendly plants was not even on the radar 10 years ago, but it surely is now.

Eight Consumer Purchasing Insights About Pollinator Plants

I read an interesting paper in the June 2017 issue of HortTechnology by researchers from the University of Georgia and the University of Florida. They surveyed the buying habits of consumers in relation to their interest in pollinators and pollinator-friendly plants. The survey was conducted in Connecticut, and approximately 850 people responded. Many esoteric points were uncovered.

Here are a few that interested me.

1. People are paying attention. About 46% of them have purchased pollinator-friendly plants and about 23% have moved to organic production practices. That is not high enough, but a significant number nevertheless.

2. While attracting pollinators was a reason to plant pollinator-friendly plants, nearly every respondent cited ornamental value and diversity (i.e., a pretty garden) as the main reasons they bought the plants. Pollinator-friendly was secondary.

3. If I had to guess why people are not bringing home pollinator-friendly plants, I would have guessed a lack of grab-you labeling. In the paper, the reason most cited for not purchasing pollinator-friendly plants was labeling, or the lack thereof.

We have been talking about labels, point-of-purchase materials, and solution-based benches set aside for issues like deer resistance and pollinators for years. Here is yet another survey that tells us there is still a lot to do.

4. Other reasons for not buying pollinator-friendly plants included higher prices and lack of diversity. It strikes me that if being a nickel more expensive (because of better labeling, packaging, etc) is the reason not to buy a pollinator-friendly plant, then the consumer was not interested anyway. Diversity (i.e., choice) is always an issue in the retail environment, from clothing to automobiles. We do the best we can.

5. A whopping 7% of the respondents thought all this hype about pollinators was just a marketing gimmick. Oh well, some people still don't wear seat belts — not much we can do. However, that still means that 93% do believe in the importance of pollinators and pollinator-friendly plants.

6. There were some interesting differences between garden centers and mass merchandisers, mainly that fewer people bought pollinator-friendly plants in the box stores and that labeling (or lack thereof) was more of a perceived problem at box stores than at garden centers. Perhaps not surprising either.

7. Older consumers buy fewer pollinator-friendly plants than do younger consumers. This is to be expected, as eco-issues such as organic practices, pollinators, etc. resonate more in younger generations. And of course, what with better digital information and the use of good garden apps, it would be expected that younger people are more aware.

8. Consumers trust information that universities and industry associations provide about pollinator-friendly plants more than from other sources, and perhaps such information in stores may carry additional weight.

The authors share some potential remedies to enhance sales of pollinator-friendly plants. Ornamental value, diversity of product, and better labeling stand out as no-brainers. What we need to do is tell pollinator plant stories in a way that motivates consumers to purchase them. Garden spending is still below 2008 levels. People spend less, and they are still intimidated about what we sell.

Pollinators and pollinator-friendly plants are a feel-good theme that we all should be touting, nay shouting. Every retail outlet and catalog, and anywhere people purchase plants should be screaming: "We are good for the environment and the world."

Bring in the green: Add plants to your reading corner, small pots by the kitchen window

NEW DELHI: Decorating with plants is one of the easiest ways to make a home feel more relaxed. Everyone can create a lush indoor garden as it can change the whole atmosphere with elements of nature.

Nikita Sethi, founder of Kalpane.in, an online marketplace for homegrown creatively made products and Gurpreet, founder of Elite Earth, gives you a few tips for a greener environment at home.

* Statement planters for your house: Try placing the plants in stands of varying heights to ensure they make a statement. Like one can always try on having an L-shaped shelve to save the floor-space and at the same time place the plants in a way that the height of each gives a statement to the room.

* Give your kitchen a makeover: The kitchen area can be used and plants can be integrating into the decor and small pots can be placed below the windows. One can try creating small vertical gardens for herbs and succulents. Cooking with fresh ingredients straight from your mini garden in the kitchen is the most exquisite thing and the welcoming décor just makes the kitchen a place to be.

* Reading nook: Plants brings the natural texture and good energy to your reading nook. A vertical plant arrangement looks like a piece of artwork and one can hang it in a corner and it will help in changing the atmosphere in the room.

* Give your home a beginning: Decorating the Hallways not just brings life to your house but the blooming flowers and the planters make it look inviting for the guests. The entrance of your house should always feel pleasant and warming and having shade plants all over the entrance just makes the house look more vibrant.

* Plants are your party saviour: It is not necessary to always have your plants on the top of the table. If you are planning for a housewarming party or a baby shower then you need to have a good table space. Tuck a couple of cement planters underneath to fill in the space with color, or use the wall hanging planters to make the space look more cool and chic.

Plants that bite

There is only one plant I know of that would actually bite you and that is the Venus Fly Trap. A bite from that plant would not be painful or even leave a bite mark. The four plants you will read about here all grow in this area and can cause mild to severe skin rashes resulting in pain, suffering, medicated creams and prescriptions.

Poison Ivy is generally the first poisonous plant that people think of. The old saying, "leaves of three let me be," refers to the three leaflets that make up one leaf. Other plants such as raspberry and boxelder have leaves that can easily be confused with Poison Ivy.

Poison Ivy plants can grow in the form of a small plant, a small bush or tree and even a vine that climbs high into trees. Virginia Creeper is another vigorous vine that climbs trees; however, it has five leaflets and is not harmful. All parts of the Poison Ivy plant contain urushiol oil that, when touched, spreads quickly on the skin due to the oily nature. Urushiol oil is very potent. One nanogram (one billionth of a gram) can cause a rash on human skin!

Poison Hemlock is a magnificent plant that found its way to ditches and fence lines in just the last few decades. I call it magnificent because it has large, shiny, beautiful, fern-like leaves. This plant is symmetrical and can grow 6 to 8 feet tall. In June, clusters of tiny white flowers appear followed by light brown seeds. All parts of this plant are poisonous to people and livestock. If you mow this plant down, be careful that juice from the stems don’t touch your skin. Blisters can form that look similar to Poison Ivy rash.

Wild Parsnip has been a common weed in the area for as long as I can remember. In the last 10 years, it has become an invasive weed in many parts of North America. It has been crowding out other friendlier ditch plants like the Foxtail and Brome grass. This plant will grow up to 5 feet topped with tiny yellow flowers in a flat, open cluster. The sap from this plant contains chemicals called furanocoumarins which, when exposed to sunlight, can cause a severe burn within 24 to 48 hours.

The fourth plant on my list can actually be eaten! Stinging Nettle when picked young can be used in salads, cooked like spinach, or steeped as a healthful tea. The problem arises when this plant gets bigger and matures. Hair-like barbs on the stems and leaf veins contain an irritant that feels like a bee sting if they touch bare skin. It is a sharp stinging pain that will go away in 10 to 15 minutes. It generally does not cause a lasting painful rash like the other plants mentioned above.

So how do you protect yourself when hiking out in nature? First and most important is to educate yourself and be able to identify these plants. Look them up and share the information with your family and friends. Then go out and try to find these plants so you know what they look like in their own home turf. Second, dress appropriately for your outdoor activity. A long-sleeved shirt and long pants with hiking boots and socks will protect you from poison plants and also ticks, mosquitos and gnats. Third, if your skin is exposed to poison plants, do not spread it by scratching or wiping your face with your hand. The oil can be easily spread, especially if you wipe sweat off your brow.

If you are "bitten," wash the exposed area with clean soapy water as soon as possible. Rinse with clear cool water. Launder your clothes to remove any residual oil. Consult a pharmacist for creams to use or seek medical help if a serious rash forms. And remember, "leaves of three let me be."

Best plants to grow in pots

There are all sorts of great reasons to grow plants in pots. You might live in a condo or townhouse with limited outdoor space. Perhaps the soil quality in your yard is poor. Or you may love the lush look of potted plants clustered around your patio or outdoor living room. Whatever your situation, find out more about the best plants to grow in pots — and the best pots to grow plants in.

Best plants to grow in pots: General tips

— The best plants for potting are those without a deep root system. Look for dwarf species or compact specimens that tend to grow upward rather than spreading outward.

— Choose plants that will do well with the amount of sun available. A balcony or deck attached to your house may offer only limited sunshine. A roof garden, on the other hand, could provide extremely strong sun, so you'll have to create some shade. Wheeled pots allow you to position your plants to catch the rays they need.

— Combine an assortment of plants in one oversize pot (or several smaller ones of different heights) for the most attractive effect. Find out what your chosen species want to do — for instance droop, clump, or climb — and mix and match accordingly.

— Consider the level of care that the plants you fancy will need. Is it compatible with your schedule and gardening skills? If not, you may want to find a professional gardener to look after your mini-landscape.

Types of plants to grow in pots

Vegetables. Most fast-growing, upward-climbing vegetable species are excellent for container gardening. Easy types to try are beans (bush beans are best), zucchini or summer squash, tomatoes, and bell peppers. NOTE: You'll need a support system ... which could be as simple as a nearby porch railing. Greens like lettuce and spinach also do well in pots.

Flowers. Go for maximum beauty, minimum maintenance. Flowers that are perennials in tropical climes (or invasive) tend to be hardy — perfect for your purpose. If you're a newbie (or even if not), geraniums are the no. 1 flower for potting. Not only do these hardy blooms thrive in containers, they provide a gorgeous array of color, delicate white to deep scarlet. Bring your potted geranium inside before the first frost, place in a sunny window, and it can live for years.

Fruit trees. Yes, fruit trees. They add so much to even a small outdoor space — good looks and with the right TLC, good eating too. Dwarf varieties are best for the confines of a pot. Check whether the fruit tree is self-fertile (such as citrus, peaches, and apricots — best if you only have room for one) or needs a partner for pollination (like apples and pears).

Best pots to grow plants in

Size. Plant pots must be deep enough to accommodate a root system — anywhere from 6-8 inches for most herbs, to 18-24 inches for a miniature tree. Potting soil is expensive, so you can add filler to the bottom third; crumbled Styrofoam works well. Make sure the base is broad enough that the pot won't tip over.

Material. Ceramic planters are ideal but tend to be pricey. UV resistant plastic pots are another option. If you want to get creative, follow the suggestion of Rodale's Organic Life and use galvanized trash cans or wooden barrels for large plantings.

Drainage. Whatever your container, ensure you have adequate drainage. Drill holes in the bottom, if necessary. Safeguard your floor, windowsill, etc., against the resulting runoff and condensation so it won't stain — or rot, in the case of a wooden deck. A saucer under the pot is a good start (TIP: water into the saucer, not the pot itself, for better absorption), but terracotta “pot feet” add an extra layer of protection.

Watering. FACT: Plants need more water in pots than in the ground. Cut down watering needs by topping the soil with mulch; great gardeners I know create decorative mulch from acorns, wine corks, or seashells. If you're planning a large-scale container garden, a drip watering system is a convenient option. For just a few potted plants, self-watering containers will reduce your workload and are handy if you're often away from home.

Research Brief: Grassland plants react unexpectedly to high levels of carbon dioxide

Plants are responding in unexpected ways to increased carbon dioxide in the air, according to a twenty-year study conducted by researchers at the University of Minnesota and published in the journal Science. For the first 12 years, researchers found what they expected regarding how different types of grasses reacted to carbon dioxide. However, researchers' findings took an unanticipated turn during the last eight years of the study.

Researchers planted 88 plots with two different types of grasses, warm-season C4 grasses and cool-season C3 grasses, and exposed them to different levels of carbon dioxide, current carbon dioxide levels and the elevated levels the Earth might experience later this century due to human activity.

"Because carbon dioxide is needed by plants to grow, we expected grasses that have the C3 photosynthetic pathway to grow more under elevated CO2, because these plants are known to be able to increase their CO2 capture as CO2 levels rise. We also expected that growth of grasses with the C4 photosynthetic pathway would not be affected by higher CO2 levels, because these plants are generally less able to capture extra CO2 as CO2 levels rise," said University of Minnesota Professor Peter Reich. "While that held true for the first dozen years, that pattern changed."

Researchers found that during the last eight years of the study, C4 plant species grew more in an elevated CO2 environment than C3 plants. While it's uncertain why this shift happened, these findings could have significant implications.

"If mature grasslands worldwide behave like our experiment did, this could have long lasting impacts on how we think about the conservation and restoration of grasslands around the world," Reich said. "Grasslands cover between 30 and 40 percent of land and play a key role in soaking up carbon dioxide released by burning fossil fuels."

Along with impacts on conservation and restoration planning, these data could be used to help computer models better predict how plants will respond to changing CO2 concentrations in the atmosphere.

"Our results suggest that the predictions made by these models might not be quite right and that we should not be overly confident about our assumptions regarding where, and by how much, land ecosystems will keep absorbing extra CO2 out of the air," Reich said.

Reich, a professor with the College of Food, Agricultural and Natural Resource Sciences' (CFANS) Department of Forest Resources and Institute on the Environment (IonE) fellow, was the lead researcher on the study. Other study investigators included Professor Sarah Hobbie and graduate student Melissa Pastore, with the Department of Ecology, Evolution and Behavior in the College of Biological Sciences, and Professor Tali Lee from the University of Wisconsin, Eau Claire.

About University of Minnesota College of Food, Agricultural and Natural Resource Sciences

The University of Minnesota College of Food, Agricultural and Natural Resource Sciences (CFANS) brings science-driven innovators together to discover hands-on solutions to global challenges. With 10 research and outreach centers across Minnesota, the Minnesota Landscape Arboretum, and the Bell Museum of Natural History, CFANS offer unparalleled experiential learning opportunities for students and the community. CFANS students enter career fields with some of the best job outlooks in the country, including 13 undergraduate majors and more than 25 minors ranging from agricultural education and marketing communications to conservation biology and forest and natural resource management, health and nutrition, to the future of food and agriculture management with a focus on business and technology.

Plants really do feed their friends

"For more than a century, it's been known that plants influence the makeup of their soil microbiome, in part through the release of metabolites into the soil surrounding their roots," said Berkeley Lab postdoctoral researcher Kateryna Zhalnina, the study's lead author. "Until now, however, it was not understood whether the contents of this cocktail released by plants was matched by the feeding preferences of soil microbes in a way that would allow plants to guide the development of their external microbiome."

The study, "Dynamic root exudate chemistry and microbial substrate preferences drive patterns in rhizosphere microbial community assembly," has just been published in the journal Nature Microbiology. The corresponding authors were Berkeley Lab scientists Trent Northen and Eoin Brodie.

Microbes within soil improve the ability of plants to absorb nutrients and resist drought, disease, and pests. They mediate soil carbon conversion, affecting the amount of carbon stored in soil or released into the atmosphere as carbon dioxide. The relevance of these functions to agriculture and climate are being observed like never before.

Just one gram of soil contains tens of thousands of microbial species. Scientists have long known that plants impact the composition of the soil microbiome in the area surrounding their roots by sending out chemicals (metabolites). Prior work by Mary Firestone, Berkeley Lab faculty scientist and a professor of microbiology at UC Berkeley, had shown that plants were consistently selecting or suppressing the same types of microbes over time in the root zone, suggesting some form of synchronization between plant and microbiome development.

Yet, little research had gone into the relationship between specific metabolites that plants release and the microbes consuming them. The new study brought together experts in soil science, microbial and plant genomics, and metabolomics to explore these potential metabolic connections. Their study took a close look at the rhizosphere of an annual grass (Avena barbata) common in California and other Mediterranean ecosystems.

The Berkeley Lab team felt the time was ripe for doing so. As pressure mounts for farmers to grow enough healthy crops to meet a burgeoning population's needs, and for new land management strategies that improve soil carbon storage to reduce atmospheric CO2 and produce healthy soils, the soil microbiome is the subject of more in-depth scientific research than ever before.

The researchers set out to determine the relationship between microbes that consistently bloomed near the grass roots and the metabolites released by the plant. Their first step was to collect soil from the University of California's Hopland Research and Extension Center in northern California. Brodie, deputy director of Berkeley Lab's Climate and Ecosystem Sciences Division, and his group used what they knew about the lifestyles of these soil bacteria to develop specialized microbial growth media to cultivate hundreds of different bacterial species. They then selected a subset that either flourished or declined as roots grew through the soil.

This collection of microbes was then sent to the Joint Genome Institute (JGI), a DOE Office of Science User Facility, where their genomes were sequenced to provide clues as to why their responses to roots differed. This analysis suggested that the key to success for microbes that thrived in the rhizosphere was their diet.

Northen, senior scientist in Berkeley Lab's Environmental Genomics and System Biology Division, is fascinated by the chemistry of microbiomes, and his group has developed advanced mass spectrometry-based exometabolomic approaches to elucidate metabolic interactions between organisms. Zhalnina and Northen combined their expertise to identify what the more successful microbes surrounding the roots of the Avena grasses preferred to eat.

Using a hydroponic setup at the JGI, they immersed plants at different developmental stages in water to stimulate them to exude their metabolites, then measured the metabolites being released by the plants using mass spectrometry. Subsequently, the cultivated soil microbes were fed a cocktail of root metabolites, and the researchers used mass spectrometry to determine which microbes preferred which metabolites.

They found that the microbes that flourished in the area around plant roots preferred a diet more rich in organic acids than the less successful microbes in the community.

"Early in its growth cycle, the plant is putting out a lot of sugars, 'candy', which we find many of the microbes like," Northen said. "As the plant matures, it releases a more diverse mixture of metabolites, including phenolic acids. What we discovered is that the microbes that become more abundant in the rhizosphere are those that can use these aromatic metabolites."

Brodie describes these phenolic acids as very specific compounds released by plants throughout their development. Phenolic acids are often associated with plant defenses or plant-microbe communication. This indicates to Brodie that as they establish the microbial community within the rhizosphere, plants could be exuding metabolites like phenolic acids to help them control the types of microbes thriving around their roots.

"We've thought for a long time that plants are establishing the rhizosphere best suited to their growth and development," said Brodie. "Because there are so many different types of microbes in soil, if the plants release just any chemical it could be detrimental to their health.

"By controlling the types of microbes that thrive around their roots, plants could be trying to protect themselves from less friendly pathogens while promoting other microbes that stimulate nutrient supply."

Zhalnina, Firestone, Northen, and Brodie believe their findings have great potential to influence additional scientific and applied research. Zhalnina points out that a lot of research and development is currently underway by government and industry to harness the power of microbes that improve plant yield and quality of soil to help meet society's growing demands for a sustainable food supply.

She said, "It's exciting that we can potentially use the plant's own chemistry to help nourish beneficial microbes within soil. Population growth, especially, has created a demand for identifying more reliable ways to manipulate the soil microbiome for beneficial outcome."

How plants 'muscle up' against bacteria in the cold

Michigan State University scientists have furthered our understanding on how a plant protein, called CAMTA, helps plants strengthen themselves as they anticipate long periods of cold, such as three to four months of winter in the American midwest or northern Europe.

The long-term goal behind the research is to breed or create plants with higher tolerance to wild swings in temperature. The study is published in the journal The Plant Cell.

CAMTA proteins are universally found across plants, and they help turn on genes that communicate freezing tolerance to these plants. In the study, CAMTA proteins were observed to also control how plants defend against harmful bacteria under long-term cold conditions.

In the cold, plants generally build up high levels of salicylic acid, or SA, a compound that protects them against bacteria.

"At warm temperatures CAMTA proteins, specifically the N-terminus (the start of the proteins), block the system that produces SA," said Yong Sig Kim, a post-doctoral student in the lab of University Distinguished Professor and MSU Foundation Professor Michael Thomashow.

When it gets cold for a long enough period, an unknown signal is generated that modifies CAMTA to allow SA production to turn on. In that case, the C-terminus, or the bottom of an amino acid chain that is stopped by a free carboxyl group, detects the signal -- possibly a rise in cellular calcium levels -- that enables SA biosynthesis.

This observation reverses current accepted models, which proposed instead that the C-terminus blocked SA production.

Why does tolerance to the cold instigate bacterial defenses?

"SA doesn't protect the plant from the cold, per se. Instead, we think the plants enhance their immune systems in the cold as a general preemptive strategy," Kim said.

Although plants take measures to survive the cold, they still get injured, and their structures are destabilized, which makes them more vulnerable to bacterial infection.

So, weakened plants keep their guard up as a precaution. It is similar to how humans take preventative measures to stay healthy – eat well, sleep eight hours, hydrate, etc.

This knowledge has long-term potential impact on agricultural production. For example, according to the EPA, in 2010 and 2012, high nighttime temperatures affected corn yields across the U.S. Corn Belt, and premature budding due to a warm winter caused $220 million in losses of Michigan cherries in 2012.

 "The field of plant defense is gradually revealing how protection mechanisms against the elements and against other living beings are interrelated," Kim said.