Phytotron Offers Oasis in the Sky

Rooftop greenhouse is home to a variety of plants and insects

Michael Mucci and Tannis Slimmon

California summers and Canadian winters are a world away from each other. But in virtual form they might end up side by side at Guelph, if a research idea involving plant and environmental scientists takes root. Before that, University researchers are already bringing various climatic regions to life in wide-ranging studies going on in the U of G phytotron.

Stand outside the Science Complex and look up. That warm glow emanating from the greenhouse glass on the roof hints at the tropics, even – or especially – on a grey November day. Yes, there’s a research greenhouse up there, but there’s more.

From climate change simulations to applied evolution studies to research meant to help feed the world, various studies are unfolding in a 13,000-square-foot suite packed with greenhouse units and growth chambers that allow researchers to run experiments under controlled conditions.

In all, about 100 researchers use the rooftop facility for projects including nitrogen in crop plants, flowering plant genetics, starch and protein metabolism, control of invasive plants, plant evolution and cold tolerance in grapes.

“We’re providing the environment they need to study plants,” says co-ordinator Michael Mucci, who joined the facility when it opened in 2005. “We can control temperature, light, humidity and carbon dioxide to whatever the researcher needs.”

Take Prof. Steven Rothstein, Molecular and Cellular Biology (MCB). His studies of nitrogen use in corn and rice occupy about one-quarter of the growth chambers at one end of the facility. “We could not do our research without the phytotron,” he says. “We have used it to screen rice lines for improved use of nitrogen fertilizer, which has both economic and environmental benefits.”

As with most other users, he comes from the College of Biological Science (CBS). About 35 research projects are based in the phytotron. Those involve 21 faculty labs, including 18 from two CBS departments: MCB and Integrative Biology. Another busy researcher up here is MCB professor Joe Colasanti, who uses about 10 per cent of those growth chambers to study genetics of plant flowering, especially in corn.

The remaining users hail from the School of Environmental Sciences (SES) and the Department of Plant Agriculture. Both departments lie within the Ontario Agricultural College, which also operates greenhouse and growth chambers for other projects in the Bovey and Crop Science buildings.

About half of the Science Complex phytotron is occupied by 45 growth chambers, including several as big as walk-in freezers. Not that anything would freeze here. Growing rice needs a temperature of about 29 C and 70-per-cent humidity. “I feel like I’m in the tropics somewhere,” says Mucci.

The chambers are controlled to keep temperatures between about 10 C and 45 C. A constant roar comes from the facility’s refrigeration units; normally people working here wear ear protection.

Water and fertilizer are supplied automatically; as with other variables, they’re electronically controlled from the phytotron’s central office.

Light in the chambers comes from a mix of fluorescent and incandescent bulbs (both are needed to provide a full range of light wavelengths for photosynthesis to occur). Energy-efficient bulbs produce light about half as intense as summer daylight – enough for plants to make themselves plenty of food.

That allows researchers to mimic the real world without setting foot outdoors. Plant physiologist Hafiz Maherali, a professor in the Department of Integrative Biology and the CBS phytotron director, says, “We can simulate light conditions that are much more realistic.” Referring to the lights in the growth chambers, he says, “Six years ago, they were brand new in North America. There was no other installation in North America then.”

Another key variable is carbon dioxide – both within the growth chambers and in the real world outside.

Harking back to his colleagues’ crop studies, he says it’s critical to balance CO2 properly in climate change simulations. Without CO2 controls in the units, corn plants would draw down the gas below required concentrations and effectively starve themselves.

Maherali now hopes to add more chambers to study climate change under varying CO2 and temperature. It’s not what you might think: he aims to look not so much at warming but at the kind of cooling happening outside the Science Complex during winter.

This is critical for farming and for natural ecosystems under climate change projections, he says. In a high-latitude country like Canada, freeze-thaw cycles will cause more winter warming and soil thawing. How will that affect plants?

“If we have capacity in the phytotron for cold temperatures and CO2 control, we can simulate what’s happening in plants and the microbes associated with them,” he says, explaining that this kind of exacting experiment is impossible in the field.

Along with SES Prof. Claudia Wagner-Riddle and other researchers, he’s planning a funding proposal for new growth chambers that would work below 10 C and even down to -10 C.

He also hopes to simulate historical CO2 levels starting before wide-scale burning of fossil fuels brought on by the Industrial Revolution. How have changes in carbon dioxide concentration since then affected the chemical reactions that drive photosynthesis?

Elsewhere, existing isolation chambers with special venting allow researchers such as MCB professors Annette Nassuth and Baozhong Meng to study plant pathogens like viruses in tomato and grape plants.

In one unusual experiment, a researcher in DNA barcoding at U of G’s Biodiversity Institute of Ontario used a chamber to hatch butterflies.

Over on the greenhouse side this fall, the bench tops were filled with plants – strawberries, tomatoes, leeks, barley and Lobelia – fed and watered by an automated irrigation system. Daytime temperatures here range from 23 C to 29 C; night time is 14 C to 19 C.

With its southerly exposure, the facility gets sun much of the day, supplemented by high-pressure sodium lighting. Shade curtains and venting help regulate temperature. Mesh screening keeps out most bugs, but it’s impossible to deter every insect pest.

Thrips are the worst invaders, not just here but in most greenhouses. Mucci and assistant co-ordinator Tannis Slimmon use biocontrols, including mites, nematodes and ladybugs. Opening a refrigerator, Mucci shows off a drawstring cloth bag containing ladybugs being kept cool and near-dormant until they’re needed. The rooftop location also deters many pests that might otherwise filter in from outside plants.

In a recent experiment, Maherali grew hundreds of plants in the greenhouse to see how they handle changes in moisture availability. Those units allowed him to mimic the periodic warming and cooling across the Pacific Ocean called the El Nino-La Nina southern oscillation that affects weather around the world. That work can help us understand how plants and their associated microbes will adapt to climate change, Maherali explains.

“We simulated extreme wet and dry years using an annual invasive plant found in the Mediterranean region. We had to grow 700 to 800 plants, each with individual watering treatments.

“The greenhouse facility in the phytotron is great because we have the ability not just to set up irrigation to program how much water is going into each pot, but we took real weather data from the Mediterranean region in California for extreme El Nino and La Nina years and simulated daily rainfall patterns for those two years.”

Some plants grown here end up downstairs in botany and ecology teaching labs. Those include researchers’ blooms as well as the fruits of Mucci’s lunch.

In a narrow space next to his central office he has cultivated a mini-tropics populated by ferns, cacti and various other plants not found in your average Canadian garden. A papaya tree soars overhead, with a couple of its fruits ripened to red-orange. Elsewhere Mucci is growing avocado, figs, pomegranates, cactus fruit, passion fruit, guava and other economically important plants.

“A lot of stuff comes out of my lunch but also through seed exchange with botanical gardens around the world,” he says. “I’ll eat an orange and plant the seeds.

Mucci also shares his greenhouse-grown seeds and spores with external partners such as botanical gardens under various biodiversity programs.

He works with Slimmon, who completed undergraduate and master’s degrees in plant agriculture in the 1980s. Standing in the light of the greenhouse, she says: “It’s a lovely environment, bright, cheery.

Along with Maherali and other CBS researchers, both are members of the college committee that runs the facility.