When one thinks of X-rays and PET scans, their mind usually goes to broken bones and early cancer detection. Dr. Yuan-Chuan Tai, associate professor of radiology at Washington University in St. Louis (WUSTL), estimates that more than 90 percent of PET scans are used for clinical oncological imaging. As a medical physicist and imaging scientist, his main focus with the technology is in clinical applications.

But building off several decades of research, Tai and scientists at the nearby Donald Danforth Plant Science Center in St. Louis are using PET scans and X-rays for another purpose: to study how plants behave.

Tracing plant mechanisms with PET scans

Tai has worked with PET scans for 26 years, but not always to advance the field of plant science. About 10 years ago, he says, the Department of Energy called for proposals from researchers who could use imaging technology to study energy crops. He applied for and received funding for plant-related imaging research. This was one opportunity that got him to do more work in that space, where he does a portion of his work still.

The Department of Energy has a wide interest in scientific research concerning “biology, environment, climate change [and] energy-producing technology,” including how plant mechanisms occur, Tai says. Much of this work has been made possible by plant imaging. For example: The Department of Energy was interested in how plants store carbon underground, and if there is a plant that can store massive amounts of carbon in its root system. All plants do this, Tai says, adding, “The goal is to understand the below-ground activity better to further improve the efficiency.”

With one of the largest PET research programs in the world, WUSTL uses four cyclotrons, or particle accelerators, to produce radioactive tracers, Tai says. These tracers allow PET to track their movement through plants, and scientists can look at processes such as carbon or nitrogen utilization, whether occurring under normal conditions or environmental changes. “If [scientists] need a new tracer to study a particular receptor, then we will work with chemists,” he says. “If they don't need a new receptor to study new a target — they just want to see where carbon goes — we don't need a chemist to be involved.”

WUSTL also received funding from the National Science Foundation to develop scanners to image plants. “Most scanners had this horizontal bore where the patient lies down in the bed [to] slide in and out of the scanner,” Tai says. “Most plants grow vertically, so we built a device and we put it inside a plant growth chamber. It has a vertical bore, so you can just drop a potted plant inside and you can scan it from top to bottom, and we can control the environment so we can study the plant.”

NSF funding also allowed Tai’s group to join the Plant Imaging Consortium (PIC) in 2014, which was formed by plant biologists and imaging specialists in Missouri and Arkansas. Tai was a co-principal investigator on the project until it ended in July. Work done through the PIC includes PET scanning of tomato plants to study carbon movement through graft junctions, as well as how roots interact with fungus and bacteria in the soil.

Additionally, WUSTL works with the Danforth Center to study interactions between plants and fungi, Tai says. “There are certain strands of fungus that can help to convert phosphor in the soil into a form that plants can consume,” he says. “Fungi pick up the phosphor and convert it — organic phosphor — they convert it, then use it to exchange for the carbon with the plant. So, plants get phosphor from fungus; fungus get carbon from plants. How they communicate and interact is an interesting scientific area.”

Mapping root structures using X-ray imaging

This specialized research is in full gear at Dr. Christopher Topp’s lab at the Danforth Center, says Keith E. Duncan, research scientist in the Topp Lab. “Chris' lab has done nothing but study root systems since it's been around — could be alfalfa, could be sorghum, could be corn, could be soybean,” he says. “Any kind of root system — we're interested in how can we measure it, how can we evaluate it, without having to pull it up out of the soil."

The Danforth Center uses an X-ray tomography instrument that is encased in a lead box, weighing eight tons and measuring about nine square feet, Duncan says. Using nondestructive imaging and leaving the plant inside intact, the machine maps root structures — everything from thickness, deepness, number and complexity.

“They sell dozens of them to automotive plants and for electronics and aerospace to do nondestructive testing and imaging of very large or very dense, very complicated things,” Duncan says. “For us, we can take entire root systems that are growing — an entire corn plant or a soybean plant growing in a one or two or three-gallon pot — put the pot in there and scan the entire root system.”

Various scanning technologies offer several levels of resolution and provide different information when imaging plant root systems, Duncan says. PET scan technology can, in millimeter-resolution, take a full image of a corn or soybean root system in a one-gallon pot, although it needs to be separated into two separate top and bottom scans to cover the entire volume of the pot. Meanwhile, an X-ray tomography machine can image an entire root system in a single three-hour scan, while providing resolution in micrometers. It also shows scientists where plant roots are — something PET technology doesn’t do.

But the answer to many biological questions can’t be answered through the use of a single technology. “Working with Tai, and then working with computer scientists, we'll take that PET scan, overlay that with the X-ray scan, which shows you where all the roots are, and now, it's like having one map overlaid with another map,” Duncan says. “You have the map of the outline of the states, and then you overlay a transparency that has all the rivers.”

The Danforth Center also performs imaging with an X-ray microscope, which was the first X-ray microscope to solely perform plant science in a plant science institute, Duncan says. “It scans roots in soil, but at a much higher magnification than the larger X-ray CT system, he says. In early August, Duncan used the X-ray to identify and examine fungi inside root tissue — marking the first time anyone has ever done this using X-ray imaging.

Applications for industry

The Danforth Center paid for the X-ray microscope along with Sumimoto Chemical and its wholly owned subsidiary Valent, the latter of which rents greenhouse space at the Danforth Center and works with the center on research. In late July, Topp and Duncan brought virtual reality headsets to the grand opening of Valent BioSciences’ Biorational Research Center in Libertyville, Illinois, allowing attendees to virtually “stand inside” the root system of a plant. Tai also attended the event.

The Danforth Center performs blind experiments with growing media that includes products from Valent and its own wholly owned subsidiary, Mycorrhizal Applications, Duncan says. “We're [currently] working out the conditions whereby we can reliably image the root system and then overlay the PET information,” he says. “Once we have that down and can measure these things consistently, then we'll start comparing roots with and without the microbes, roots with and without the additives, roots with the additive plus and minus a drought condition or nitrogen starvation.”

Overlaying X-ray and PET scans is one process that makes data management and analysis so integral to the Topp Lab’s work, Duncan says. The lab employs as many computer scientists and mathematicians as it does biologists, with the former two groups working on projects like the virtual reality visualizations.

Duncan says he expects that Danforth Center research that looks at beneficial bacteria and fungi and how they feed nutrients to plant roots will have an impact on the ornamental industry. Although corn is a much different crop from ornamentals, the genetic controls for their root systems will often be similar. As the industry better understands root system architecture, it will be able to introduce useful soil additives.

Greenhouse growers, unlike field growers, have the ability to control their environment, Tai says. They could benefit from plant imaging research to add to that control. “If they have a better understanding of certain mechanisms underlying the growing cycle of plants, or to understand which species should be under certain kinds of growth conditions, then they can potentially fine-tune their greenhouse environment to maximize their yield,” he says. “I can imagine [this would help] them to have a better understanding of the greenhouse environment and how the conditions affect the productivity. That would actually have some commercial value.”

“In the spring a young man's fancy lightly turns to thoughts of love. Spring is the season for love.” — Alfred, Lord Tennyson.

But for most of us, our fancy turns to the welcoming display of spring flowering bulbs after a long and dreary winter. Brightly colored daffodils, tulips and more adorn both public and private landscapes reviving our spirits. There are many people behind the scenes who make that happen, and Becky Heath of Brent and Becky’s Bulbs is one of them.

Becky was born in Richmond, Va., about 60 miles west of Gloucester where she now resides and it’s the home of Brent and Becky’s Bulbs. As the middle child and the only girl, she would follow her dad around, helping with the chores which included working in the vegetable garden, and taking care of the chickens, rabbits and pigs on the farm. The first plant she fell in love with was a zinnia when her dad gave her a packet of seeds when she was just 8 years old.

But her journey to bulbs took a long, convoluted path. Becky started singing just before she was 3 years old and performed for almost 10 years on a weekly children’s program on WRVA radio in Richmond called “Talented Tots” and “Junior Jamboree” during the late 40s and early 50s. She attended Virginia Commonwealth University and graduated with a degree in music and education. Right out of college she began teaching vocal music first at the high school level then to the intermediate level which included orchestra and chorus, challenging her to combine the two types of groups together for performances. She ended up in Gloucester when a private school needed a music teacher and a second-grade teacher.

As a teacher she would meet with parents to discuss their child’s progress. One of the parents was concerned about his child because he and his wife were going through a divorce and was worried about the effect on his son. He would call every month to check on his son. The man was Brent Heath who would eventually become Becky’s husband and business partner.

After they were married, Brent asked Becky to help him with his business, which at the time was called Daffodil Mart. Brent was the third-generation owner and his mother, Katie Heath, was in the office every day. Back then, the only thing they sold were daffodil bulbs from their 10-acre farm. Becky knew nothing about daffodils but knew how to balance a checkbook, stick to a budget and how to keep records. She proved to be a quick study and learned about hybridizing daffodils and creating new types (which was her favorite part). It was around that time the Heaths realized they needed more room to grow their bulbs.

The business was embarking on many changes. Brent was taking more plant photos and was being asked to give talks about daffodils more often, which he enjoyed. The farm, with its 3,000 types of daffodils, was attracting growers from around the world who were looking for something new to grow. Other growers suggested that they could take 200 bulbs of one type and increase them to larger quantities a lot faster than the Heaths could, so Brent and Becky partnered with some outside growers. Around this same time, customers were requesting that the farm grow and sell tulips, not just daffodils.

Brent and Becky toured the fields of their contract growers, making sure the cultivars were labeled correctly and checking for diseases. During those tours, they were inspired by the tulip fields to fulfill their customers’ requests and began growing and selling tulips.

But like true love, the path didn’t run smoothly. The Heaths sold their company to another firm. The terms of the contract associated with the sale were broken, and the pair were forced to start all over again. When asking for advice about a new company name, one of their customers said, “It really doesn’t matter as long as your name is on it, so we know it’s you.” At the time, most of their orders came in by phone or mail. But having the name Heath came across as “Heee” when answering the phone, so it became Brent and Becky’s Bulbs.

Finding their best roles

When they started they had 10 acres on the home farm but now have an additional 18 acres, 8 of which are for Becky’s “Teaching Garden” and the rest for greenhouses and propagation fields.

“When I married Brent, he was still only growing daffodils and for the first five years, we only sold what we grew on the farm and again, we only grew daffodils. So, we were farmers,” Becky recalls. “The first year we were married, we probably shipped a couple of thousand daffodil bulbs a year. And many were sold one bulb at a time because they were rare. Now we handle millions of different types of bulbs.”

They also deal with contract growers all over the world.

“We developed relationships with growers who only wanted to grow and not have catalogues or customers,” she explains. “Many are from the U.S. and others are from Holland, Israel, England and South Africa — from wherever the bulbs grow best. So, we probably produce about 20 percent [of the products we sell] here on site. The rest are from other places.”

They’ve since expanded to also grow perennials and tropical plants.

In 2000, they developed a bulb planting machine that can plant up to 30,000 bulbs in an hour. There are two options: one for flat areas and another for hillsides. It helps create a huge splash of color when most things are still not blooming. Their son Jay runs the machine and it has been used at many public gardens in the United States.

Starting out in this industry she met some obstacles, feeling like she was an ornament rather than a contributor. But as time passed and she learned more about the bulbs and the business, she was viewed as a teacher who was sharing information. She also published two books, “Tulips for North American Gardens” and “Daffodils for North American Gardens,” which boosted her credibility. And people began to realize that while Brent was doing the talking, she was the one doing the walking — the woman behind the man.

“Becky excels at both horticulture and business. She travels extensively to promote the bulb business and champion all things horticultural at meetings and conferences across the country,” says C. Colston Burrell, principal at Native Landscape Design and Restoration. “She designed, and Brent maintains, an extensive garden showcasing the myriad hardy and tender plants offered by the nursery as well as durable, heat tolerant herbaceous and woody plants that thrive in the Mid-Atlantic region. All the while she keeps Brent and Becky’s Bulbs running like a well-oiled machine, organizing orders and keeping customers smiling.”

Brent enjoys talking about the bulbs rather than being in the field and dealing with equipment. Becky’s teaching background made her want to provide more information to the customers, which she implemented in their catalogues along with cultural information and planting instructions.

Sharing the joys of plants and gardening is what drives Becky.

“We know we are not the largest [company] and that has never been what’s important to us. We try to be the best. The best product with the best information and service — at least that is our goal,” Becky says. “We do our best to help new gardeners choose bulbs and plants that will be successful in their area and not choose because of a pretty picture. We hope to share the joys of gardening and help people to play in their gardens.”

Becky is spreading the word in many ways including being the current president of GWA, The Association for Garden Communicators.

She sees the industry evolving. Large companies are buying up smaller companies, and a large portion of the last couple of generations have either decided that growing their own food isn’t important or they are too busy to do so. There are fewer hobby gardeners now from what she’s observed. But the positive news is that she sees “an intense interest from those same couple of generations of having clean air to breathe, clean drinking water and eating a healthy diet. So I feel like if we address the goals of these busy people and figure out how to fulfill what is important to them, we as a horticultural industry will survive and so will the earth.”

For more: www.brentandbeckysbulbs.com

Denise is a professional horticulturist and garden writer based in Pittsburgh.

Pesticides can have direct and/or indirect effects on natural enemies; such as, parasitoids and predators. Direct effects are associated with acute mortality or survival (longevity), over a specified period of time, of the life stages of natural enemies including the egg, larva, nymph or adult. Indirect effects involve inhibition of feeding behavior (for predators) and parasitism (for parasitoids); a decrease in female reproduction; and a reduction in foraging behavior.

These indirect effects may be associated with repellency. The effects of repellency on natural enemies are considered indirect or sublethal due to potential influences on foraging behavior and orientation (physical direction or position of something). Any indirect adverse effects of pesticides due to repellency can interfere with foraging behavior and parasitism. In fact, a number of insecticides are known to have repellent activity with potential effects on the foraging or searching behavior of natural enemies. Repellency is primarily affiliated with reduced contact by natural enemies with a host (prey) treated with an insecticide. Therefore, repellency may decrease parasitoid and predator efficiency by reducing the probability of encountering prey, which can lead to a change in spatial distribution of predators and parasitoids; and more importantly, a reduction in regulating insect or mite pest populations. The factors that can influence repellency include: pesticide formulation, residual activity (persistence) and pesticide susceptibility to sunlight (ultra-violet light) degradation.

It is important to understand that repellency can prevent natural enemies from effectively regulating pest populations; thus leading to increases in pest populations overtime. A strong repellent effect can prevent individuals from contacting pesticide residues, which could result in a reduction in the number of eggs laid and offspring produced; consequently decreasing the number of individuals in future generations. This will decrease the ability of natural enemies to effectively regulate pest populations.

Bifenthrin and permethrin (pyrethroids), and chlorpyrifos and malathion (organophosphates) are insecticides with repellent activity. In fact, many pyrethroid-based insecticides are known repellents acting on the sensory nervous system, which can affect foraging, feeding and reproduction. Natural enemy responses to the repellent effects of pyrethroids may be an innate behavioral adaptation to reduce the risk of exposure to pesticide residues. These insecticides may repel (or even irritate) predators by acting directly on the central or peripheral nervous system. Botanical insecticides may also have repellent effects on natural enemies, which can reduce the time spent by adults searching for hosts (prey) on leaves and diminishes the number of prey attacked by predators or eggs laid into prey by female parasitoids.

Check AIs and inert ingredients

Furthermore, certain fungicides have repellent effects on natural enemies such as the predatory mite, Phytoseiulus persimilis, which could reduce the ability of the predatory mites to effectively regulate twospotted spider mite (Tetranychus urticae) populations. It should be noted that any repellent effects may not be attributed to the active ingredient of a given pesticide but instead to the inert ingredients (e.g. adjuvants) in the formulation. If a pesticide is needed to help an existing biological control program, be sure to read the label thoroughly and if necessary contact the manufacturer to obtain information associated with any repellent effects of a given pesticide (insecticide, miticide or fungicide).

Raymond Cloyd is a professor and extension specialist in horticultural entomology/plant protection in the Department of Entomology at Kansas State University. His research and extension program involves plant protection in greenhouses, nurseries, landscapes, conservatories and vegetables and fruits. rcloyd@ksu.edu or 785-532-4750

Research trials have been and continue to be conducted on wood-containing substrates across the country at academic institutions, private industry laboratories and at numerous grower operations. Data from these trials are slowly becoming public, just as the need and demand for results, observations, recommendations and testimonials have never been higher. While we have some answers about using wood substrates, we find ourselves having as many new questions as we do confirmed answers. Here is some of what we do know and are seeing in today’s evolving production practices and research trials.

Feeding the hunger

Dating back to the early 2000s and confirmed more recently with follow-up trials, it has been discovered that to grow plants in wood substrates or very high percentages of wood in substrates required some significant changes to plant-growing practices. The first of two approaches that were uncovered involved the increase of fertility (fertigation) to the tune of an additional 100 ppm nitrogen in 100 percent pine wood compared to 80:20 peatlite for optimal and equivalent crop growth. This was repeated with multiple species including lighter feeding plants like marigolds or heavier feeders like mums. The extent of nitrogen supplementation that a grower must add depends on 1) traditional fertility practices (standard ppm N applications); 2) percent of wood substrate in the mix; 3) type of wood component; 4) age and properties of wood component; 5) irrigation and fertility delivery method.

The second approach to improving plant growth in wood substrates is to increase the percentage of peat. Some of the first trials conducted many years ago showed that plant growth increased at lower fertility levels as the percent peat increased. This was not shocking or unforeseen due to the inherent properties of wood versus peat, but what was very interesting was the fact that plants could be grown very successfully at 150 ppm N with rates of wood close to 50 percent. Now, fast forward to today when basically all trials (academic, industry and grower) are conducted with peat:wood blends (not 100 percent wood like a decade ago) and the results often indicate that wood can be amended with peat at rates of 30 to 50 percent with a high level of success. Again, caution is offered, as there are many variables that can make this scenario successful for some and not so successful for others. Rates of wood amendment to peat are still more comfortably recommended in the range of 10 to 40 percent.

The nutrient (primarily nitrogen) immobilization that occurs in wood substrates is still a very complex issue that is very difficult to analyze and quantify. Researchers have tried for decades to device adequate, simple, and reproducible tests to measure nitrogen tie-up but to-date few options are available. One method used in Europe (some evidence that it is occurring here in the U.S. as well on a small scale) is a nitrogen impregnation technique. Wood substrate manufacturers who employ this technique will incorporate granular nitrogen into wood chips prior to processing (extrusion devices). During the thermo-mechanical fiberization (wood chip to fiber) the fertilizer is “impregnated” into the wood fiber (Fig. 2). Upon incorporation of the wood fiber into peat (or other material), no supplemental fertility is needed, as the wood now contains the extra nitrogen needed to compensate for any tie-up activity that may impact plant growth and performance.

Getting physical with peat

Wood can make peat better. Yes, I said it. Wood should not be viewed as a peat replacement or even a major threat to peat producers and/or products. Instead, I offer the idea (after many mistakes and after eating much crow) that wood products can enhance certain peat mixes and create opportunities for new peat-based product development. Look around at what many of the Canadian and European peat producers are doing — embracing wood as a component, while not neglecting the use and promotion of peat. How can wood make peat better or make mixes better? For one, the unique physical marriage of peat and wood fibers is a beautiful thing to witness. When wood fiber is blended with peat at rates as low as 10-20 percent, the two materials interlock, forming a matrix that is now a unified and structured substrate. This is very different than peat and perlite blends, which even after mixing remain forever separate. The union of peat and wood fibers creates a physical environment that is high in overall porosity, high in airspace, has great water capture abilities (less hydrophobic), good drainage properties, good water retention and movement, high substrate humidity, no-splashing or separating or floating during irrigations, and a playground for fast developing and aggressive roots.

In addition to the “substrate matrix” effect that wood and peat create when blended, the physical environment that they create in regard to water holding and air space percentages is desirable. When blended with 100 percent peat at rates of 10, 20, 30, and 40 percent (by volume), wood fibers (pine tree substrate, GreenFibre, Forest Gold and HydraFiber) show excellent water-holding capabilities as well as increases to air space in the substrate environment (Fig. 3). It has been reported and confirmed over and over that as the percent wood fiber/component increases, the air porosity of peat mixes will increase similar to perlite. This interaction is one of the reasons that many growers are adopting wood components in their mix instead of perlite. More will be discovered and revealed relative to the role of wood components as true alternatives to perlite in the near future. The implications here are huge.

The green revolution

Emerging crops are also high-priority areas for substrate researchers and manufacturers. With tremendous growth in controlled environment food, fruit and cannabis production comes new opportunities for traditional and new substrates that are being released throughout the growing media industry. The number of new mixes (most containing wood and/or perlite-free) released just in 2018 is staggering. The possibilities are endless when one considers not only the immense value of food crops but also the continuing legalization of cannabis (in one form or another) across the country. Some researchers here at North Carolina State University are now fully engaged in cannabis substrate research to assist growers and the substrate industry with substrate-related development and use for this “new” crop (Fig. 4). Expanding and emerging markets for growing media will continue well into the future. Wood fiber, in some form or fashion, is here to stay and now should be considered a viable growing media component and no longer just an “alternative.”

So, what’s the verdict for wood fiber? The jury may still be out for some, but others are fully onboard and publicly expressing their excitement and support for the adoption and use of wood substrates (with peat) as part of their production protocols. So, what say you?

Brian is an associate professor and director of the Horticultural Substrates Laboratory at NC State University. He can be reached at Brian_Jackson@ncsu.edu