̽��ֱ�� of Cambridge - Fruit

Metallic blue fruits use fat to produce colour and signal a treat for birds

sc604 — Thu, 06 Aug 2020 15:00:00 +0000

̽��ֱ��plant, Viburnum tinus, is an evergreen shrub widespread across the UK and the rest of Europe, which produces metallic blue fruits that are rich in fat. ̽��ֱ��combination of bright blue colour and high nutritional content make these fruits an irresistible treat for birds, likely increasing the spread of their seeds and contributing to the plant’s success.

̽��ֱ��researchers, led by the ̽��ֱ�� of Cambridge, used electron microscopy to study the structure of these blue fruits. While there are other types of structural colour in nature – such as in peacock feathers and butterfly wings – this is the first time that such a structure has been found to incorporate fats, or lipids. ̽��ֱ��results are reported in the journal Current Biology.

“Viburnum tinus plants can be found in gardens and along the streets all over the UK and throughout much of Europe — most of us have seen them, even if we don’t realise how unusual the colour of the fruits is,” said co-first author Rox Middleton, who completed the research as part of her PhD at Cambridge’s Department of Chemistry.

Most colours in nature are due to pigments. However, some of the brightest and most colourful materials in nature – such as peacock feathers, butterfly wings and opals – get their colour not from pigments, but from their internal structure alone, a phenomenon known as structural colour. Depending on how these structures are arranged and how ordered they are, they can reflect certain colours, creating colour by the interaction between light and matter.

“I first noticed these bright blue fruits when I was visiting family in Florence,” said Dr Silvia Vignolini from Cambridge’s Department of Chemistry, who led the research. “I thought the colour was really interesting, but it was unclear what was causing it.”

“ ̽��ֱ��metallic sheen of the Viburnum fruits is highly unusual, so we used electron microscopy to study the structure of the cell wall,” said co-first author Miranda Sinnott-Armstrong from Yale ̽��ֱ��. “We found a structure unlike anything we’d ever seen before: layer after layer of small lipid droplets.”

̽��ֱ��lipid structures are incorporated into the cell wall of the outer skin, or epicarp, of the fruits. In addition, a layer of dark red anthocyanin pigments lies underneath the complex structure, and any light that is not reflected by the lipid structure is absorbed by the dark red pigment beneath. This prevents any backscattering of light, making the fruits appear even more blue.

̽��ֱ��researchers also used computer simulations to show that this type of structure can produce exactly the type of blue colour seen in the fruit of Viburnum. Structural colour is common in certain animals, especially birds, beetles, and butterflies, but only a handful of plant species have been found to have structurally coloured fruits.

While most fruits have low fat content, some – such as avocadoes, coconuts and olives – do contain lipids, providing an important, energy-dense food source for animals. This is not a direct benefit to the plant, but it can increase seed dispersal by attracting birds.

̽��ֱ��colour of the Viburnum tinus fruits may also serve as a signal of its nutritional content: a bird could look at a fruit and know whether it is rich in fat or in carbohydrates based on whether or not it is blue. In other words, the blue colour may serve as an ‘honest signal’ because the lipids produce both the signal (the colour) and the reward (the nutrition).

“Honest signals are rare in fruits as far as we know,” said Sinnott-Armstrong. “If the structural colour of Viburnum tinus fruits are in fact honest signals, it would be a really neat example where colour and nutrition come at least in part from the same source: lipids embedded in the cell wall. We’ve never seen anything like that before, and it will be interesting to see whether other structurally coloured fruits have similar nanostructures and similar nutritional content.”

One potential application for structural colour is that it removes the need for unusual or damaging chemical pigments – colour can instead be formed out of any material. “It’s exciting to see that principle in action – in this case the plant uses a potentially nutritious lipid to make a beautiful blue shimmer. It might inspire engineers to make double-use colours of our own,” said Middleton, who is now based at the ̽��ֱ�� of Bristol.

̽��ֱ��research was supported in part by the European Research Council, the EPSRC, the BBSRC and the NSF.

Reference:
Rox Middleton et al. ‘Viburnum tinus Fruits Use Lipid to produce Metallic Blue Structural Colour.’ Current Biology (2020). DOI: 10.1016/j.cub.2020.07.005

Researchers have found that a common plant owes the dazzling blue colour of its fruit to fat in its cellular structure, the first time this type of colour production has been observed in nature.

I first noticed these bright blue fruits when I was visiting family in Florence. I thought the colour was really interesting, but it was unclear what was causing it

Silvia Vignolini

What gives this metallic blue fruit its colour?

Rox Middleton

Viburnum tinus fruits

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Pollinator species vital to our food supply are under threat, warn experts

fpjl2 — Fri, 26 Feb 2016 10:20:44 +0000

Delegates from almost 100 national Governments have gathered in Kuala Lumpur to discuss how to address the threats facing animal pollinators: the bees, flies, birds, butterflies, moths, wasps, beetles and bats that transport the pollen essential to the reproduction of much of the world’s crops and plant life.

It is the first time the global community has gathered on this scale to focus on the preservation of the small species that help fertilise more than three quarters of the leading kinds of global food crops and nearly 90% of flowering wild plant species.

A report on pollinator species produced over two years by an international team of 77 scientists, including Cambridge’s Dr Lynn Dicks, has been adopted by the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) today. IPBES has 124 member Governments.

̽��ֱ��report is the first assessment ever issued by IPBES, and the first time that such an assessment has brought together multiple knowledge systems comprehensively, including scientific, and indigenous and local knowledge. It will highlight the threats to animal pollinators, and the major implications of these species’ declines for the world’s food supply and economy.

But the report also details the ways that pollinator power can be used for the benefit of biodiversity, food security and people: by harnessing natural relationships between plants and animals to improve agricultural yields and strengthen local communities.

“It is incredible to see international Governments coming together to discuss the problem of pollinators in this way,” says Lynn Dicks, from Cambridge ̽��ֱ��’s Department of Zoology.

“Without pollinators, many of us would not be able to enjoy chocolate, coffee and vanilla ice cream, or healthy foods like blueberries and brazil nuts. ̽��ֱ��value of pollinators goes way beyond this. People’s livelihoods and culture are intimately linked with pollinators around the world. All the major world religions have sacred passages that mention bees.”

̽��ֱ��volume of pollinator-dependent food produced has increased by 300% over the past 50 years, including most fruits from apple to avocado, as well as coffee, cocoa, and nuts such as cashews. This shows an increasing dependence of agriculture on pollinators.

Such crops now occupy around 35% of all agricultural land. While these crops rely on animal pollination to varying degrees – along with, for example, wind-blown pollination – the scientists estimate that between 5 and 8% of all global crop production is directly attributable to animal pollinators, with an annual market value that may be as much as 577 billion US dollars.

However, the experts warn that a variety of agricultural practices are contributing to steep declines in key pollinating species across Europe and North America. In Europe, populations are declining for at least 37% of bee and 31% of butterfly species.

A lack of data for Africa, Latin America and Asia means we are currently in the dark about the status of pollinators in many parts of the world, say the scientists. Where national ‘red lists’ are available, they show that up to 50% of global bee species, for example, may be threatened with extinction.

For some crops, including cocoa, wild pollinators contribute more to global crop production than managed honey bees. Wild bee populations are of particular concern, as bees are “dominant” pollinators, say scientists, and visit over 90% of the leading global crop types.

Changes in land-use and habitat destruction are key drivers of pollinator decline. Increasing crop monocultures – where the same plant is homogenously grown across vast swathes of land – mean that the plant diversity required by many pollinators is dwindling.

Increased use of pesticides are a big problem for many species – insecticides such as neonicotinoids have been shown to harm the survival of wild bees, for example – and climate change is shifting seasonal activities of key pollinators, the full effects of which may not be apparent for several decades.

̽��ֱ��decline of practices based on indigenous and local knowledge also threatens pollinators. These practices include traditional farming systems, maintenance of diverse landscapes and gardens, kinship relationships that protect specific pollinators, and cultures and languages that are connected to pollinators.

Everyone should think carefully about whether they need to use insecticides and herbicides in their own gardens

Many livelihoods across the world depend on pollinating animals, say scientists. Pollinator-dependent crops include leading export products in developing countries (such as coffee and cocoa) and developed countries (such as almonds), providing employment and income for millions of people.

If the worst-case scenario – a complete loss of animal pollinators – occurred, not only would between 5 and 8% of the world’s food production be wiped out, it would lower the availability of crops and wild plants that provide essential micronutrients to human diets, risking vastly increased numbers of people suffering from Vitamin A, iron and folate deficiency.

However, the assessment says that by deploying strategies for supporting pollinators, we could not only preserve the volume of food they help us produce, but we could boost populations and in doing so could even improve production in sustainable farming systems, so-called “ecological intensification”.

Many pollinator-friendly strategies are relatively straightforward. Maintaining patches of semi-natural habitats throughout productive agricultural land would provide nesting and ‘floral resources’ for many pollinators. This could be as simple as strips of wild flowers breaking up crop monocultures, for example, and identifying and tending to nest trees in farming settings.

Certain traditional crop rotation practices using seasonal indicators such as flowering to trigger planting also help to maintain diversity – and it is diversity that is at the heart of flourishing pollinator populations.

There are actions that Governments around the world could take, says Dr Dicks, such as raising the standards of pesticide and GMO risk assessment, or supporting training for farmers in how to manage pollination and reduce pesticide use. National-level monitoring of wild pollinators, especially bees, would help to address the lack of long term data on pollinator numbers.

“There are many things individual people can do to help pollinators, and safeguard them for the future,” says Dr Dicks.

“Planting flowers that pollinators use for food, or looking after their habitats in urban and rural areas, will help. Everyone should also think carefully about whether they need to use insecticides and herbicides in their own gardens.”

More information about how to help wild pollinators can be found at the Bees Needs website, which is part of the National Pollinator Strategy for England.

Inset image: Lynn Dicks at the IPBES meeting in Kuala Lumpur.

A new report from experts and Government around the world addresses threats to animal pollinators such as bees, birds and bats that are vital to more than three-quarters of the world’s food crops, and intimately linked to human nutrition, culture and millions of livelihoods. Scientists say simple strategies could harness pollinator power to boost agricultural yield.

People’s livelihoods and culture are intimately linked with pollinators around the world. All the major world religions have sacred passages that mention bees

Lynn Dicks

Dino J. Martins/Nature Kenya

Carpenter bee (Xylocopa flavorufa) visiting coffee flower (Coffea arabica)

̽��ֱ��text in this work is licensed under a Creative Commons Attribution 4.0 International License. For image use please see separate credits above.

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