Plants

U of T plant biologists find answers to pollination mystery blowing in the wind

noreen.rasbach — Tue, 29 Jan 2019 21:15:51 +0000

U of T plant biologists find answers to pollination mystery blowing in the wind

noreen.rasbach Tue, 01/29/2019 - 16:15

Cutline

A fly pollinator visitis a female flower of Thalictrum pubescens (tall meadow-rue). Females of this species produce stamens with sterile pollen grains, presumably to reward pollinators (photo by David Timerman)

Sean Bettam

Topic

Our Community

Ecology & Environmental Biology

Faculty of Arts & Science

Graduate Students

Plants

Research & Innovation

New research by scientists at the ��Ƶ offers novel insights into why and how dozens of flowering plant species evolved from being pollinated by insects to being pollinated by wind.

Although insect pollination is more economical, numerous lineages have reverted back to wind pollination, leaving many biologists to question why that would ever happen given the success of insect pollination. This apparent paradox perplexed even Charles Darwin, and still today, little is known about the conditions initiating this transition.

In a study published recently in Proceedings of the Royal Society B, the researchers describe for the first time a mechanism driving this reversion involving the vibration of stamens, the pollen-bearing organs of flowers.

“We found that plants in which stamens vibrate more vigorously in wind, disperse pollen by wind more readily, and that this characteristic of stamens is favoured under conditions where plants receive few visits from pollinators,” said lead author David Timerman, a PhD candidate working with evolutionary biologist Spencer Barrett in the department of ecology and evolutionary biology in the Faculty of Arts & Science at U of T.

The discovery helps to explain the origins of wind pollination, which is represented in approximately 10 per cent of flowering plant species.

“It may also be useful for understanding how plants will cope with a reduction in pollinator services due to the global collapse of wild pollinator populations,” said Timerman.

The reproductive structures of flowering plants are the most diverse of any group of living organisms. Flowers vary extensively in size, shape and structure, and much of this diversity is related to modes of pollination. Wind-pollinated species have independently evolved several traits adapted for releasing, dispersing and capturing pollen in air, one of which involves long flexible stamens that vibrate conspicuously in wind.

Why and how wind pollination has evolved in flowering plants from animal pollination is a long-standing fundamental question in the evolutionary biology of plants. Early seed plants depended on wind to carry pollen between plants, but about 100 million years ago, flowering plants evolved to attract insects that could transfer pollen with greater precision than random air currents. While wind pollination has since evolved from animal pollination on at least 65 occasions in flowering plants – trees, ragweed and many grasses among them – the mechanisms involved in the transition are not well understood.

It has been long held by scientists that wind-pollinated plants are aerodynamically engineered for efficient pollen dispersal. But compared to animal-pollinated species few studies have investigated the function of floral traits associated with wind pollination. Moreover, the modifications of flowers required for the evolutionary switch from insect to wind pollination have not been studied because until now, there have been no experiments on transitional species that are both wind and insect-pollinated.

“We took a novel approach to this problem by applying biomechanics to understand the key processes involved in the early stages of this transition, and the work provided several novel insights,” said Timerman.

Representative examples of flowers with high (left) and low (right) natural frequency stamens. Flowers were stored in 60 per cent ethanol and photographed using a dissection microscope (photo by David Timerman)

Timerman and Barrett examined the problem in a species called Thalictrum pubescens, of the buttercup family. The plant is an ambophilous species, meaning it is pollinated by both insects and wind. As such, they speculate that the species probably represents a transitional state in the evolution of wind pollination.

Timerman used an electrodynamic shaker to apply controlled vibration to stamens to measure their natural frequency of vibration, then used a custom-built wind tunnel to investigate how the natural frequency of vibration influences pollen release. Timerman also performed a manipulative field experiment at U of T’s Koffler Scientific Reserve to confirm whether natural selection acts differently on stamen properties in the presence or absence of insect pollinators.

Timerman measured variation in the natural frequency of the stamen’s vibration across nine populations, and assessed the repeatability of vibration frequency over consecutive growing seasons. With all of the data they collected, the researchers analyzed the effect of this parameter on pollen release in the wind tunnel, as well as male reproductive success of plants in the field with and without pollinators.

“Successful reproduction was greatest for plants whose stamens vibrated at a lower frequency when pollinators were absent, but this advantage diminished when pollinators were present,” said Timerman. “Our biomechanical analysis of the wind-flower interface has identified this naturally occurring feature as a key trait for understanding early stages in the transition from insect to wind pollination.”

Timerman says when animal pollinators do not provide adequate pollination services, natural selection should favour individuals with flexible stamens that vibrate readily, releasing pollen into the air.

“Wind is obviously a more consistent agent for pollen dispersal than relying on insects whose population sizes and behaviours fluctuate in time and space” says Timerman. “Further, many aspects of global environmental change are currently disrupting pollinator service to wild plants, leading to what has been termed ‘the pollination crisis’.

“These situations could potentially favour the evolution of wind pollination through the mechanism that we have discovered.”

Support for the research was provided by the Natural Sciences and Engineering Research Council of Canada.

Escape the winter gloom and surround yourself with nature at this new U of T library exhibit

Romi Levine — Tue, 29 Jan 2019 18:03:19 +0000

Escape the winter gloom and surround yourself with nature at this new U of T library exhibit

Romi Levine Tue, 01/29/2019 - 13:03

Cutline

Orchidaceae of Mexico and Guatemala weighs a whopping 38 pounds and features life-sized illustrations of orchids (photo by Romi Levine)

Topic

Thomas Fisher Rare Book Library

U of T Libraries

Subheadline

Nature on the Page at the Thomas Fisher Rare Book Library explores the Victorian obsession with flora and fauna

Long before Beatlemania, there was beetlemania, the seaweed craze, orchidelerium and fern fever.

Victorians in the mid-1800s were obsessed with the natural world, spawned by an abundance of print material on natural history at price points that could reach almost anyone, from aristocrats to working-class families.

These publications taught people how to grow, preserve and sketch plant specimens they acquired or collected and, in turn, Victorians created their own print material to document the flora and fauna they were observing.

Beginning today, ��Ƶ’s Thomas Fisher Rare Book Library will be showcasing its collection of Victorian natural history at Nature on the Page: The Print and Manuscript Culture of Victorian Natural History.

The exhibition is curated by Maria Zytaruk, a U of T alumna and an associate professor of English at the University of Calgary. Her work centres on the history of collecting and the history of museums, particularly with regards to plant specimens and their preservation.

Much like today’s clothing trends, which only become popular when they reach fast-fashion chains, natural history reached widespread popularity when publications were available at a low price, says Zytaruk.

“Victorian natural history didn't proliferate until it could reach down lower into the book market in inexpensively produced handbooks,” she says.

One-shilling guides (pictured above) about everything from ferns to microscopes made nature accessible. They allowed people to bring the wilderness into their homes – even if it was just a modest plant in a soapbox on a windowsill.

The exhibition includes a number of the mass-produced, one-shilling handbooks, as well as some unique items, including a 38-pound book with life-sized illustrations of orchids.

“It's a beautiful mammoth book. It's like the Audubon of orchids,” says Zytaruk.

Orchidaceae of Mexico and Guatemala by James Bateman would have been sent to a small subscriber base of high-end orchid collectors and people with conservatories, says Zytaruk.

The vast majority of the book was illustrated by women, including Sarah Anne Drake, whose manuscripts are also owned by Fisher library.

“I've really tried to highlight the role of women as illustrators and authors of these books, and as collectors and artists,” says Zytaruk.

Treasures of the Deep by David Landsborough (pictured above, top centre), includes what may appear at first glance to be an illustration of bright pink seaweed. In fact, it fooled Zytaruk when she first saw it.

“As I looked at it more closely I realized it was a specimen of seaweed preserved from the 19^th century,” she says.

It got Zytaruk thinking about the number of specimens needed to fill the approximately 100 books that were circulated.

Victorians had preservation in mind when collecting plant and animal specimens, but their obsession had a detrimental effect on the nature they were trying to immortalize, she says.

“They were collecting to preserve, but many species became threatened and some were extinguished entirely – fern species, seaweed species, birds, various plants, native orchids,” says Zytaruk. “There were tensions between preservation and loss.”

Nature on the Page will be on display until April. Free curator-led tours will take place on Feb. 1, 21 and March 14.

(Left) A fern specimen, added to A Systematic Arrangement of British Plants by an enthusiastic reader, and an illustration of an orchid in Orchidaceae of Mexico and Guatemala

Drought-resistant plants: U of T study looks at the crucial role root microbiomes play

noreen.rasbach — Wed, 24 Jan 2018 20:05:54 +0000

Drought-resistant plants: U of T study looks at the crucial role root microbiomes play

noreen.rasbach Wed, 01/24/2018 - 15:05

Cutline

For the study, Connor Fitzpatrick grew 30 species of plants found in the Greater Toronto Area from seed in identical soil mixtures in a laboratory setting – with some involving simulated drought conditions

Topic

Research & Innovation

U of T Mississauga

Just as the micro-organisms in our gut are increasingly recognized as important players in human health and behaviour, micro-organisms are critical to the growth and health of plants, a new study by a ��Ƶ researcher has found.

For example, plants that are able to recruit particular bacteria to their root microbiomes are much more drought resistant, says Connor Fitzpatrick, a PhD candidate in the department of biology at U of T Mississauga.

The plant’s root microbiome is the unique community of micro-organisms living in and on plant roots. Similar to the gut microbiome in animal species, the root microbiome is the interface between a plant and the world. The root microbiome is responsible for important functions such as nutrient uptake and signals important to plant development.

Fitzpatrick is the lead author of a study published in the latest issue of the Proceedings of the National Academy of Science. His exploration of the role of the root microbiome in plant health could eventually assist farmers to grow crops under drought-ridden conditions.

For the study, Fitzpatrick (pictured left) grew 30 species of plants found in the Greater Toronto Area from seed in identical soil mixtures in a laboratory setting. These included familiar plants like goldenrod, milkweed, and asters. The plants were raised for a full growing season (16 weeks), with each species grown in both permissive and simulated drought conditions.

Fitzpatrick’s research explores the commonalities and differences among the root microbiomes of the various host plant species, dividing the microbiomes into the endosphere (microbes living inside roots) and rhizosphere (microbes living in the soil surrounding roots). He found variation across the 30 species, with related species having more similarity between microbiomes than diverse species.

“It’s as you would expect,” Fitzpatrick says. “Just as there are more similarities between a human’s gut microbiome and an ape’s than between a human’s and a mouse’s, the closer the relationship between plant species, the more similar their root microbiomes. It’s important to document as a way to better understand the evolutionary processes shaping the plant root microbiome.”

Interested in publicly funded research in Canada? Learn more at U of T’s #supportthereport advocacy campaign

In addition to deepening our basic biological understanding of plant evolution and development, the research offers further avenues for study, including how and why some plants recruit bacteria that impact drought resistance while others don’t.

“If plants were able to enrich their root microbiomes with a particular group of bacteria, the Actinobacteria, they grew much better in drought conditions,” says Fitzpatrick. “All of our plants had access to this group of bacteria, but they also needed to have the ability to recruit it from the soil.”

In another finding that is consistent with the practice of crop rotation, Fitzpatrick showed that the more similar the composition of a plant’s root microbiome to that of the previous generation of a plant grown in that soil, the more the second-generation plant suffered.

“There is a complex web of interactions taking place that is difficult to disentangle and requires further inquiry,” Fitzpatrick says.

Read the research

“Practically speaking, we need to understand how to sustain plants with all of the mounting stressors today, such as drought and an increase in pathogens (for example, plant disease),” Fitzpatrick says. “The efforts to mitigate these issues are expensive and short-lived or very damaging to the environment. If we can harness naturally occurring interactions for these purposes, we’ll be much better off.”

The research was supported by Canada's Natural Sciences and Engineering Research Council (NSERC).

Forget the lines at High Park: check out U of T's cherry blossoms

geoff.vendeville — Fri, 21 Apr 2017 21:10:55 +0000

Forget the lines at High Park: check out U of T's cherry blossoms

geoff.vendeville Fri, 04/21/2017 - 17:10

Cutline

There are no long lines for the cherry blossoms outside Robarts Library (photo by Geoffrey Vendeville)

Geoffrey Vendeville

Author legacy

Geoffrey Vendeville

Subheadline

Peak bloom is expected over the weekend or early next week, arborist says

Each spring, large crowds descend on High Park to behold the majesty of its many cherry blossoms – and shamelessly snap selfies.

For those who prefer quieter surroundings, U of T's Robarts Library provides a welcome option. A path cutting across the grounds from Huron Street to Harbord Street is flanked by 70 Japanese cherry trees, also known as sakura.

The university received the trees through the Sakura Project, an initiative of the Consulate General of Japan in Toronto.

Kristen McLaughlin, a master's of museum studies student, snapping pictures of the cherry blossoms. The trees remind her of Vancouver, she says (photo by Geoffrey Vendeville)

They have flowered each year since 2005, providing students with a peaceful oasis, especially during exam season.

Diana Teal, the executive director of the High Park Nature Centre and a certified arborist, told U of T News that the trees near Robarts will reach peak bloom April 23-25.

They are in the fifth stage in the bloom process, the “puffy white stage,” she said, adding, “That is absolutely the scientific name for it.”

“Given that it's going to be warm and a little warmer where you are because you're surrounded by buildings and concrete, you're close to peak bloom for sure,” she said.

The cherry blossoms have a relatively short blooming period. Their flowers are said to last only four-to-ten days. Last year, many cherry blossoms in Toronto didn't flower at all because of erratic weather.

The cherry blossoms cut a stark figure against the brutalist concrete architecture of Robarts (photo by Geoffrey Vendeville)

“I've seen the trees at U of T, and I know it's a beautiful little spot,” Teal said. “If you're going to have a moment with the trees and enjoy that rite of spring, going to a different park is a good option because the crowds in High Park can be overwhelming.”

Although it may be tempting to handle the trees to snap a perfect picture, Teal reminds visitors to be respectful.

“By their nature, the cherry trees can be rather fragile,” she said. “We've seen five people sitting on a limb together, and the limb falls off,” she said of the trees in High Park. “If you love the trees, treat them with respect – as you would any living thing.”

Sofia Vitorino, an ESL student visiting U of T, takes a selfie amid the cherry blossoms outside Robarts (photo by Geoffrey Vendeville)

Hager Jahim, an English major, took a study break by going for a stroll among the trees on Thursday.

“It's really pretty,” she said. “I've never seen something like this before.”

It was a campus visit to U of T that led her to choose to study here.

“I went on a tour and I was like, 'Wow.' I was so fascinated by all the buildings, and it's such a nice campus,” she said.

The cherry blossom is meant to be a symbol of goodwill and friendship between the governments of Ontario and Japan (photo by Geoffrey Vendeville)

The trees outside Robarts aren't the only ones at the university.

Another well-kept secret among local cherry blossom-connoisseurs are the 50 trees at U of T Scarborough between the H-Wing and Social Science building.

Avoid the lines at High Park by checking out the sakura grove at U of T Scarborough (photo by Kristina Doyle)

U of T researchers find plants evolving to adapt to urbanization-driven environmental conditions

ullahnor — Fri, 06 Jan 2017 14:32:20 +0000

U of T researchers find plants evolving to adapt to urbanization-driven environmental conditions

ullahnor Fri, 01/06/2017 - 09:32

Cutline

Frost-covered clover (photo by Marc Johnson)

Blake Eligh

Author legacy

Blake Eligh

Topic

A tiny plant is providing big clues about how urbanization is driving the evolution of living organisms.

New research from U of T reveals the first evidence that the common white clover changes genetically to adapt to urban environments.

The study by U of T Mississauga researchers Ken Thompson and Marc Johnson also reveals surprising new information about the effect that city temperatures may play in the process. Marie Renaudin of AgroSup Dijon is a co-author on the paper, which appears in the journal Proceedings of the Royal Society B.

“Humans build cities and live in them, but many other organisms live in our cities too,” says Thompson, who conducted the research while working on a master’s degree in ecology and evolutionary biology at U of T. “We wanted to see whether natural populations are adapting to urbanization. We also wanted to understand the ecological features of cities that might be driving such adaptations.”

The researchers studied white clover, which is commonly found in both urban and rural environments. Established traits of the plant include cyanogenesis, a poisonous chemical defence system that protects clover from herbivores.

When crushed, chemicals in the leaves combine to create hydrogen cyanide, which deters slugs and other creatures from eating the plant. But the chemical protection comes at a cost – if the clover freezes, those same compounds harm the plant. As a result, clover has evolved to be less likely to display cyanogenic traits in cold climates and more likely to display cyanogenic traits in warm climates.

“We saw this as the ideal model system to test if organisms adapt to cities,” says Johnson, an associate professor of biology at U of T Mississauga. “We know clover adapts to temperature variation at continental scales, and we know there are similar temperature changes across cities like Toronto, New York, Montreal and Boston.”

The research team sampled thousands of plants from clover populations along 50-kilometre paths between the urban core of Toronto and rural areas outside the city, looking for evidence of evolutionary changes in cyanogenic traits.

Air temperatures in cities are often a few degrees higher than surrounding rural areas due to a sparse tree canopy and acres of asphalt and concrete that absorb and reflect the sun’s heat. Because of this “urban heat island effect,” the researchers expected to find evidence of cyanogenic traits in urban clover.

“We expected the urban plants to have more cyanide in the city because warmer temperatures would result in less freezing,” says Thompson, who is now working on his PhD at the University of British Columbia. “But we found the exact opposite – populations are evolving decreased levels of cyanide toward the urban centre.”

The same pattern was repeated in clover samples from Boston and New York City.

“Data tells us that the air temperature is warmer in the city centre,” Thompson says. “We needed temperature data from the plant’s perspective.”

The team monitored ground-level temperature sensors over the winter. The sensors revealed a surprise – despite warmer urban air temperatures during the day, it is much colder at ground level in the city centre at night than it is in the country. They called it the “urban cold island effect.”

By analyzing satellite images, the researchers concluded that snow cover played a crucial part in the process.

“Snow is a great insulator of the ground so plants buried under snow are much warmer than plants that are not,” Thompson says. “Rural populations are more insulated by snow, but we found a decrease in snow cover in urban populations, leaving plants exposed to cold temperatures. This appears to cause natural selection for plants that lack cyanogenic traits in cities.”

The sole outlier in the study was Montreal, which experiences more urban snow cover than the other cities in the study.

“We’re learning that organisms are rapidly adapting to the unique environmental conditions associated with urbanization,” Thompson says. “We know a lot about the climates of cities, but this research shows that cities are having surprising effects on living organisms. We need more data on how evolution is happening to understand the effect of urbanization on living organisms.”