Biology News & Research

The cloud forests of Brazil, by R. Oliviera, one of the plant scientists behind this new research

How does water travel through a plant? Your answer's probably a simple one. Water moves from the soil, up through the roots and stems of a plant, through the leaves and out into the surrounding atmosphere.

But recent research has shown that our traditional understanding of the movement of water through plants is incomplete. Under certain specialised conditions, some plants have evolved the ability to absorb water through their leaves, move it down the xylem, and them release it into the soil. The plants are actually watering their own roots - and their own seedlings. This off-beat mechanism for water uptake works well enough that these plants can continue to photosynthesise and grow, even when the soil they are growing in are dry.

The trees the researchers studied - Drimys brasiliensis - grow in the cloud forests of Brazil, where the trees are almost constantly covered in fog.  The atmosphere around the leaves has a higher water potential than the leaves themselves, allowing foliar water uptake. The exact pathway for water entry is still under discussion: this particular species has a hydrophilic cuticle that could facilitate water entry, as well as hydrophilic tissues within the leaf that could provide water storage.

At least 70 species, across seven different ecosystems, have been identified as using this  'back-to-front' water transport mechanism, pulling water out of the sky and down to the rhizosphere.  

These new findings have important implications for our existing models of the climate and our ecosystems, which often consider soil water as the only source of water for plants.

It's another example of how plants are constantly over-turning our expectations.

Eller, C. B., Lima, A. L. and Oliveira, R. S. (2013), Foliar uptake of fog water and transport belowground alleviates drought effects in the cloud forest tree species, Drimys brasiliensis (Winteraceae). New Phytologist, 199: 151–162. doi: 10.1111/nph.12248

Read a full open access commentary in the New Phytologist

Read the abstract of the original article in the New Phytologist

Read a blog post on this article in the Annals of Botany blog.

Read a blog post on this article in the New Phytologist blog.

We think of caffeine as being a plant defence mechanism - a chemical compound produced to deter possible insect predators. And as we sip our morning cup of coffee, feeling our brains become more alert and our memory better, most of us assume it's just a lucky chance that causes caffeine to have such beneficial effects on us humans.

So why, a team of plant scientists asked, do flowers produce caffeine in their nectar? Surely deterring pollinating insects from nectar would be an evolutionary dead-end?

What's more, since the human relationship with caffeine is relatively recent, its impact on our brains is most likely to be by-product of its true ecological role.

The team investigated, and found that caffeine can enhance bees' memory, making them more effective pollinators of those particular plants. By adding just enough caffeine to their nectar - not enough to make it bitter, but enough to have a pharmacological effect - the plants were more likely to be pollinated and to set seed, out-competing their neighbours

In a paper published in Science, 8 March 2013, the team concluded:

"Plant defense compounds occur in floral nectar, but their ecological role is not well understood. We provide evidence that plant compounds pharmacologically alter pollinator behavior by enhancing their memory of reward. Honeybees rewarded with caffeine, which occurs naturally in nectar of Coffea and Citrus species, were three times as likely to remember a learned floral scent as were honeybees rewarded with sucrose alone. Caffeine potentiated responses of mushroom body neurons involved in olfactory learning and memory by acting as an adenosine receptor antagonist. Caffeine concentrations in nectar did not exceed the bees' bitter taste threshold, implying that pollinators impose selection for nectar that is pharmacologically active but not repellent. By using a drug to enhance memories of reward, plants secure pollinator fidelity and improve reproductive success." 

Read more online

The Daily Mail have called it ‘Ashmageddon’. Could a fungus brought into the UK with imported trees devastate our native woodland and environment?

How can your students use their scientific knowledge to understand this threat?

Thousands of people have been outside checking ash trees for signs of infection by the fungal pathogen Chalara fraxinea and informing the authorities of their findings.

Chalara fungal spores attack the leaves first, before the disease moves up the leaf stems and into the branches and trunk, eventually blocking the water-carrying xylem vessels, starving them of moisture and killing the tree. Strict plant biosecurity rules have been implemented across the UK.  A major programme of research, habitat surveying and citizen science has been proposed.

The Guardian’s Teacher Network gives a good list of resources.

Looking at ash dieback and using these resources gives you the opportunity to:

•    Demonstrate to students why it is important to be able to identify plants correctly
•    Practice plant identification skills and make a real contribution to research currently underway (students with smartphones can use the Ashtag app to upload sightings)
•    Explore the structure and function of xylem in trees to understand why Chalara is so dangerous
•    Introduce ideas about epidemiology and how disease spreads throughout populations
•    Discuss the pros and cons of GM in relation to the resurrection of chestnuts in the USA through this Nature article

In addition, we have two related SAPS practicals:

• SAPS Practical - Deadly diseases and plant pathologists
  

In this new practical, students track down leaf pathogens under the microscope, as a starting point to consider the global impact of disease on society and the environment. The topic would make a contemporary science club activity, but is relevant to many aspects of A-level biology, such as leaf structure during the teaching of photosynthesis, productivity of crop species and reasons for using pest control.

• SAPS Practical - Bats, bees and ash keys
  

What do ash trees, bees and bats have in common? The surprising answer is in their wings - or, in the case of the ash trees, their winged fruits . Recent research shows that the wings of these fruits, like hovering insects and bats, generate more lift than would be expected by regarding the wings as aerofoil sections - an example of convergent evolution across animals and plants. In this practical, students design an investigation to look at the relationship between the length of winged fruits and their flight capacity. Plenty of opportunities for data gathering and analysis!

8 October 2012

Today's drugs might become even more effective overnight - by pairing them with compounds from plants.

Researchers at the US Department of Agriculture looked at the effects of pairing conventional antifungal medicines with compounds such as thymol, a compound produced by thyme plants.

The team focused on different species of Aspergillus mould, which can infect corn, cotton, pistachios, almonds and other crops, and can produce aflatoxin, a natural carcinogen. Aflatoxin-contaminated crops must be identified and removed from the processing stream, at times resulting in large economic losses. However, the US researchers have built up a collection of plant-based compounds targeting one particular Aspergillus species, A. flavus, either killing it or preventing it from producing aflatoxin.

A. flavus and two of its relatives, A. fumigatus and A. terreus, may impact the health of immunocompromised individuals exposed to the fungus in moldy homes. In a 2010 article in Fungal Biology, the team reported that thymol, when used in laboratory tests with two systemic antifungal medications, inhibited growth of these fungi at much lower-than-normal doses of the drugs.

Using plant-derived compounds to treat fungal infections is not a new idea, nor is that of pairing the compounds with antifungal medicines. But the team's studies have explored some apparently unique pairs, and have provided some of the newest, most detailed information about the mechanisms likely responsible for the impact of powerful combinations of drugs and natural plant compounds.

Read more at Science Daily

Questions to ask yourself

• Why do plants produce compounds, such as thymol, with antifungal properties? What are the advantages for the plant?
• Where in the plant are these compounds produced?
  
• How does plant breeding effect levels of active compounds in herbs and other plants?
  

Related resources

• Medical matters: investigating antimicrobials (Student project started, suitable for extended projects or Advanced Higher investigations)
• Plants as chemical factories (Science club activity)
  

3 August 2012

Have you ever stepped out into a narrow city street and began to cough? You may have been a victim of the way that 'street canyons' trap polluted air, keeping harmful substances like nitrogen dioxide and microscopic particular matter at exactly the right heights for people to breathe them it.

However, scientists at the Universities of Birmingham and Lancaster argue that by ‘greening up’ our streets a massive 30% reduction in pollution could be achieved, according to research published in the journal Environmental Science and Technology.

Plants growing in the concrete-and-glass urban canyons of cities can deliver cleaner air at the roadside, where most of us are exposed to the highest pollution levels, and can be implemented street-by-street without the need for large-scale and expensive initiatives.

So Transport for London has now constructed its first green walls to help combat the Capital's air pollution. The latest, installed just in time for the Olympics, is at The Mermaid event centre in Blackfriars (shown in the photo, right). This 200 square-metre wall is made up of 15 varieties of emission-trapping plants which help reduce locally generated pollution, particularly from nearby busy roads. Best of all, it looks gorgeous, as well as improving health.

Carefully selected varieties of plants remove pollutants including nitrogen dioxide and microscopic particulate matter, both of which are are significant problems in cities in developed and developing countries: UK Government Environmental Audit Committee estimates are that outdoor air pollution causes 35,000-50,000 premature deaths per year in the UK, while the World Health Organization’s outdoor air quality database puts the figure at more than 1 million worldwide.

Originally, researchers thought that planting green walls would have only a small effect on urban pollution, but the Birmingham and Lancaster teams have reversed this theory. The researchers have found that, because pollution cannot easily escape street canyons, ‘green walls’ of grass, climbing ivy and other plants have a better opportunity than previously thought to act as an air pollution filter. Instead of reducing pollution by 1 or 2%, reductions of more than ten times this magnitude could be achieved, according to this study.

Using a computer model that captures the trapping of air in street canyons, as well as the hundreds of chemical reactions that can affect pollution concentrations, the research team could distinguish the effects of plants in canyons from those of plants in parks or on roofs. Green walls emerged as clear winners in terms of pollutant removal. Street trees were also effective, but only in less polluted streets where the tree crowns did not cause pollution to be trapped at ground level.

The researchers even suggest building plant-covered "green billboards" in these urban canyons to increase the amount of foliage.

20 July 2012

"Thousands of years ago massive elephantlike creatures wandered the landscape, gobbling up then defecating fruit. In the process, they may have planted the seeds for primordial forests. But with these creatures long extinct, ecologists have been left with a puzzle: If these trees are still with us, what—if anything—disperses these seeds to create today's woodlands?

The answer—at least for one type of forest—may lie in the criminal antics of a cunning rodent. A group of scientists working with the Smithsonian Tropical Research Institute in Panama and Wageningen University in the Netherlands report their hypothesis in today's Proceedings of the National Academy of Sciences.

The rodent in question is the agouti—a house cat–size critter that resembles a leggy, tailless squirrel. Although an agouti cannot devour large tropical fruits the way an ancient mammoth might have, it consumes the seeds, collecting and burying some to store as snacks for later.

Traditionally, the agouti has been described as a seed predator. Studies monitoring their caches suggest that it doesn't take long for an agouti to come and collect. However, the research published today suggests that caching a fallen seed is just the beginning of a seed-stealing saga that carries each over long distances."

Read the rest of the story - and see a video of the thieving rodents in action - on the Scientific American website.

Herbal preparations of thyme could be more effective at treating skin acne than prescription creams, according to research presented at the Society for General Microbiology’s Spring Conference in Dublin this week. Further clinical testing could lead to an effective, gentler treatment for the skin condition.

Researchers from Leeds Metropolitan University tested the effect of thyme, marigold and myrrh tinctures on Propionibacterium acnes – the bacterium that causes acne by infecting skin pores and forming spots, which range from white heads through to puss-filled cysts. The group found that while all the preparations were able to kill the bacterium after five minutes exposure, thyme was the most effective of the three. What’s more, they discovered that thyme tincture had a greater antibacterial effect than standard concentrations of benzoyl peroxide – the active ingredient in most anti-acne creams or washes.

Dr Margarita Gomez-Escalada who is leading the research project explained how tinctures are made from plants and herbs. “The plant material is steeped in alcohol for days or even weeks to prepare a tincture. This process draws out the active compounds from the plant. While thyme, marigold and myrrh are common herbal alternatives to standard antibacterial skin washes, this is the first study to demonstrate the effect they have on the bacterium that causes the infection leading to acne,” she said. The researchers used a standard in vitro model that is used to test the effect of different substances applied to the skin. The effects of the tinctures were measured against an alcohol control – proving their antibacterial action was not simply due to the sterilizing effect of the alcohol they are prepared in.

These initial findings pave the way for more research into the use of tinctures as a treatment for acne. “We now need to carry out further tests in conditions that mimic more closely the skin environment and work out at the molecular level how these tinctures are working. If thyme tincture is proven to be as clinically effective as our findings suggest, it may be a natural alternative to current treatments,” explained Dr Gomez-Escalada.

A herbal treatment for acne would be very welcome news - particularly for acne sufferers who experience skin sensitivity. “The problem with treatments containing benzoyl peroxide is the side-effects they are associated with,” said Dr Gomez-Escalada. “A burning sensation and skin irritation are not uncommon. Herbal preparations are less harsh on the skin due to their anti-inflammatory properties while our results suggest they can be just as, if not more, effective than chemical treatments.”

10 May 2012

They're known as "ghost trees," and for good reason: albino redwoods are extremely rare and nearly impossible to spot. There may be as few as 25 of these trees in the world, yet eight of them are at Henry Cowell Redwood State Park in Northern California.

These trees are not just pale: they're dead white, and their needles are limp and waxy - 'the exact color of a glow-in-the-dark star you might find in a kid's bedroom', says science journalist Amy Standen. A genetic mutation has prevented them from producing chlorophyll, and the result is that they're entirely unable to photosynthesize.

So how can a plant not only survive, but grow, without the ability to produce its food? "Without chlorophyll, they can't photosynthesize...  The only reason that albino redwoods survive at all is that they are connected at the root to a parent tree from which they will suck energy for their entire lives," Amy Standen says. "It's like some 40-year-old who refuses to get a job, keeps eating his parents' food and sleeping in his old bedroom. In the case of the redwoods, this arrangement can last a century, or more - and no one knows why." Or you could see these trees as vampires - surviving only by sucking life from others.

But this isn't just an intriguing insight into photosynthesis. The albino redwoods have a lot to tell us about the process of evolution.

Park ranger Dave Kuty explains that redwoods are hexaploid, meaning they have six sets of chromosomes, rather than the two sets of chromosomes that humans have. "Genetically speaking, coastal redwoods are playing with a much bigger deck of cards than we humans are. There are more genetic combinations possible," as Amy puts it. Redwoods are thought to be the most adaptable tree on earth by being able to change their genes so readily. "Every time a sprout comes up with slightly different genes, it's kind of like an experiment. If it works, that tree might set the course for the generations of the future.They can develop resistance to fungi. They can develop resistance to viruses. They can develop better growth patterns," Dave explains. But, because these mutations are random, some of the new traits developed are no use at all - positively harmful, in fact.

"Albinos probably aren't a particularly good modification, from the standpoint of the health of the forest, but they demonstrate there's a lot of experimentation going on," Dave says. And in the long term, a few parasitic albino trees are worth it, for all the benefits that this genetic variation can bring.  

Listen to the full radio story from National Public Radio

April 5, 2012

Cambridge researchers have developed a new technique for measuring and mapping gene and cell activity through fluorescence in living plant tissue.

A new technique using fluorescence to automatically measure and map cellular activity in living plant tissue will contribute to better computer models that are at the heart of synthetic biology, the attempts to engineer living systems.

The team at the University of Cambridge’s Department of Plant Sciences, led by Dr Jim Haseloff, have been working to uncover the mysteries of biological systems in certain plants – characterised by the highly complex genetic and cellular networks which are locked in a vast network of interactions – resulting in self-repair and reproduction in the organism.

These evolved biological systems are capable of creating structures of a hugely complex nature, far more sophisticated than the most advanced man-made materials – which the plants do in a renewable and, if it could be harnessed, a potentially very cheap way.

By creating new techniques allowing ever more detailed study of the cellular activity of plants, scientists believe it may be possible to reprogram living systems – which has given rise to an emerging field known as Synthetic Biology, which applies engineering principles to the building blocks of organic life.

“Synthetic Biology is based on the use of reusable components and numerical models – for the design of biological circuits, in a way that has become routine in other fields of engineering,” says Haseloff.

“Techniques such as the one we have developed will help us to discover more about the thrilling complexities of life at this level, and how we might be able to utilise the power of plants and their cellular networks in engineering – potentially revolutionising the way we engage with organic matter.”

At the moment, Synthetic Biology is in its infancy, and there is a critical need for improved techniques for measuring biological parameters within still living systems of cells.

This new technique – outlined in a paper published on the Nature journal’s Methods website on Sunday – involves fluorescent proteins, such as those originally found in certain jellyfish and corals. The proteins are used to mark and consequently identify specific parts of cells – the nuclei and membrane – mapping the development, position and geometry of the cellular make-up in the living plant tissue.

The researchers combine the advanced imaging processes with algorithms that automate quantitative analysis of cell growth and genetic activity within living organisms to precisely reconstruct cellular dynamics – and produce a numerical description that can be used to inform computer models.

In this way the cellular properties in intact plant tissue can be observed in depth – and be converted to mathematical descriptions of the living processes. This opens the door for the construction of new computer models for Synthetic Biology and the engineering of living tissue.

Adds Haseloff: “We have been able to use the very latest technical advances in microscopy for quantitative analysis of cell size, shape and gene activity from images of living plant tissues. This new technique, which we call in planta cytometry, will contribute to a greater understanding of plant development, physiology and help pave the way for advances in biological engineering.”

From Research News, University of Cambridge website

What do sunflowers, pioneering computer scientist Alan Turing and the Fibonacci sequence have to do with each other?

Turing is famous today for his mathematical and code-breaking skills and his work on the Enigma machine during the Second World War. But Turing was also fascinated by the mathematical patterns found in plant stems, leaves and seeds, a study known as phyllotaxis. After the war, this formed a key element of his research at the University of Manchester.

Turing noticed that the number of spirals in the seed patterns of sunflower heads and pine cones often conform to a number that appears in the mathematical sequence called the Fibonacci sequence (0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89…). This could hold crucial insights into the way that plants develop and grow.

The Manchester Science Festival team explain more: "Sadly, he died before his work was complete and since then scientists have continued his work, but to properly test these hypotheses we need lots of data… and sunflowers are perfect for the job, so long as we can grow enough of them!"

They're asking people across the country to grow sunflowers, with a view to sending in their data to the project when they flower. The results will then be analysed by the Manchester scientists.

So if you're up for the challenge, sign up here.