Biology News & Research

26 September 2011

An unwary insect that finds itself on the rim of a pitcher plant doesn't have long to live. Not only do the pitcher plants (Nepenthes) have deep cavities to trap their prey, but the rims of these cavities are exceptionally slippery - and their biology has just inspired a scientist at Harvard University to develop a new material so slippery that no liquid can stick to it. The result could be cleaner surgical instruments, walls that are impervious to graffiti, car windscreens that can't ice up, and much more.

The rims of Nepenthes, called the peristomes, have a series of complex adaptations that cause insects to aquaplane along the surface and fall into the pitcher. Researchers at Cambridge University looked at the peristomes under a microscope, in order to understand just how they were so slippery.

Science journalist Ed Yong describes their findings: "[The peristome] is lined with cells that overlap one another, creating a series of step-like ridges and troughs. The plant secretes nectar onto this uneven surface. The troughs collect the nectar, and the ridges hold it in place, preventing it from draining away. The result is an extremely smooth, stable and slippery surface that repels the oils on the feet of insects." By capturing these insects, the plants gain an additional source of nitrogen, allowing them to thrive in nutrient-poor soils.

Tak-Sing Wong has mimicked the Nepenthes peristomes to create a new synthetic material which is ten times as slippery as the next most slippery synthetic. 

His surfaces "are made of either stacks of tiny posts, each a thousand times thinner than a human hair, or a random network of similarly thin fibres. These provide a rough structure, which Wong filled with a lubricant, just as the pitcher plant saturates its rough cells with nectar. The lubricant mixes with neither water nor oils, and it barely evaporates," explains Yong.

Find out more and see the vidoes of the slippery surface in action at Discover Magazine.

Find

16 August 2011

For the last six years an international team of plant scientists have been working in the rainforest in Panama, looking at the potential effects of climate change on the rainforest ecosystem. Among the research underway was a careful study of the role of litterfall – the dead plant material such as leaves and bark that builds up on the ground under the trees. The group hypothesised that, as climate change stimulates increased growth in tropical forests, that litterfall would increase in turn, and that this would have a significant impact on the soil.

Tropical forests play an essential role in regulating the carbon balance. It is thought that trees will respond to rising levels of carbon dioxide by with increasing growth, and taking up more carbon. However, increased tree growth will result in more leaves, and hence more litterfall. 

Plant scientist Dr Emma Sayer, who has a fellowship that has seen her spending time in both Cambridge and Panama, chose to investigate three key questions: What interactions exist between fine roots in the soil and litter in the forest floor? Does increased litterfall cause loss of soil carbon through priming effects? What are the relative contributions of roots and litter to total soil respiration? Over the years, she has carefully worked on a number of test plots on the Gigante Peninsula in the Barro Colorado Nature Monument. "In brief, we remove all the litter from five 45-m x 45-m plots once a month and add it to five others, leaving five undisturbed as controls," Dr Sayer says. 

Her study now concludes that that a large proportion of the carbon sequestered by greater tree growth in tropical forests could in turn be lost from the soil. She and her colleagues estimate that a 30% increase in litterfall could release about 0.6 tonnes of carbon per hectare from lowland tropical forest soils each year. This amount of carbon is greater than estimates of the climate-induced increase in forest biomass carbon in Amazonia over recent decades. Given the vast land surface area covered by tropical forests and the large amount of carbon stored in the soil, this could affect the global carbon balance.

Dr Sayer says “Most estimates of the carbon sequestration capacity of tropical forests are based on measurements of tree growth. Our study demonstrates that interactions between plants and soil can have a massive impact on carbon cycling. Models of climate change must take these feedbacks into account to predict future atmospheric carbon dioxide levels.”

Find out more at the University of Cambridge's Research News website.

24 August 2011

New research suggests that the familiar landscapes we see around the world today – the rivers, fertile plains, and rich forest ecosystems - were shaped around 330 million years ago by the steady evolution of plants. And in turn, these landscapes would eventually encourage the growth of settled farming societies, shaping human society. 

We've often heard about how deforestation can lead to barren and vulnerable landscapes, with water washing away the soil, which is no longer held together by tree roots. So what would the ground have looked like in a world without any kind of roots at all? 

“The continuing evolution and expansion of land plants irrevocably altered the alluvial landscape,” write Neil Davies and Martin Gibling, in an article published in Nature Geoscience, August 2011. The team of paeleobotanists and geologists from the Dalhouseie University, Nova Scotia, have been conducting numerous field trips and analysing over 330 published studies of river channels in rock strata, to link together the evolution of key features in plants with the changing landscape in the Carboniferous period.

Animals came onto land before the ancestors of our modern plants, so these early organisms were arriving in a world that was already inhabited by potential 'predators'. We might find it difficult to recognise these plant ancestors as such - these early plants had no conducting tissues (phloem and xylem), and so were severely limited in size, nor did they have any roots.

"Shallow rooting first becomes apparent in Lower Devonian (Lochkovian) strata as a mechanism for water supply and stabilising arborescent vegetation. Subsequently, as the size and diversity of arborescent vegetation increased through the later
Devonian and Carboniferous, the depth and diversity of rooting increased dramatically. ... With Carboniferous plants using an increasingly diverse array of morphologies and life strategies, plant groups would have interacted in various ways with their environment," the scientists write.

Davies and Gibling postulate that without these tight root networks holding the soil particles together, early rivers were not confined to channels as they usually are today, but instead tended to flood across the landscape in shallow. The result might perhaps have looked more like a perpetually moving flood than what we think of as a river.

When tree-like plants with deep roots developed some 330 million years ago, they could hold together soil, limiting the spread of river channels.  "This would have greatly boosted the stability of the entire floodplain," write the authors. Rather than spreading broadly across the landscape, rivers became single, deeper channels, the landscape we know today.

The landscape these newly-evolving plants created supported new ecosystems in its turn. These stable lowlands with fixed rivers are well watered and could develop deep, organic soil, which allowed rich ecosystems to systems. Flood plains also provide fertile farmland for humans, which probably acted to encourage more settled societies. 

Find out more about the research at Nature Geoscience online.

If you'd like to explore plant evolution and development for yourself, why not take a look at the Plant Evolution timeline, an interactive online presentation of plant evolution created by members of the University of Cambridge's Department of Plant Science for their students. It's particularly interesting to look at the evolution of new species by selecting 'Species and Speciation' (lower graph), the development of roots, stomata and conducting tissues, ('Physiological Developments' on the lower graph) and the changes in carbon dioxide (on the top graph). 

30 July 2011

Look around you. All over the world, plants are harnessing the sun’s energy to split water molecules, causing oxygen to be released. It’s a process that needs nothing more than light, carbon dioxide, water – and some immensely sophisticated biochemistry on the part of the plants.

For years, scientists have dreamt of creating ‘artificial leaves’ – power sources that would need as few and as simple inputs as real leaves do. These could produce energy for billions of people in parts of the world where electricity is currently unavailable or unreliable.

Now, researchers at MIT, one of the USA’s foremost universities, have taken an important step towards making the dream a reality. Their prototype ‘artificial leaf’ combines a standard silicon solar cell with a catalyst developed by Prof Dan Nocera and his team. When immersed in water and exposed to sunlight, the ‘leaf’ causes bubbles of oxygen to separate out of the water. Again, they’ve learnt from biochemistry to develop their new technology. “The catalyst has the same structure as the leaf’s water-splitting machine but with cobalt instead of manganese,” Prof Nocera explains.

The next step to producing a usable ‘artificial leaf’, the team reports, is to integrate an additional catalyst to bubble out hydrogen molecules. These could then be used to generate electricity or to make fuel for vehicles.

The MIT news office reports: “ultimately, Nocera wants to produce a low-cost device that could be used where electricity is unavailable or unreliable. It would consist of a glass container full of water, with a solar cell with the catalysts on its two sides attached to a divider separating the container into two sections. When exposed to the sun, the electrified catalysts would produce two streams of bubbles — hydrogen on one side, oxygen on the other — which could be collected in two tanks, and later recombined through a fuel cell or other device to generate electricity when needed.”

Read all about it on the MIT news website

Or see Professor Nocera talk about his dream of personalised energy through 'artificial leaves' (discussion of photosyntehsis begins at 12.28)

Japanese astronauts are taking cucumbers into space in a major new experiment to understand off-planet plant growth.

We all know that plants are fundamental to life on Earth, not only providing the oxygen we breathe, but the food we eat as well. For long term space missions to be carried out successfully, the astronauts will need to take plants with them. But how will plants respond to the environment of a space station, and in particular, the lack of gravity?

The first study on cucumbers by the Japan Aerospace Exploration Agency (JAXA) looked at directional root growth. They found that, rather than growing downwards, under microgravity the cucumber roots grew sideways.

In the latest study, the team will investigate whether hydrotropism can be used to control the direction of root growth in microgravity.

The NASA website reports that "To perform the HydroTropi experiment, astronauts transport the cucumber seeds from Earth to the space station and then coax them into growth. The seeds, which reside in Hydrotropism chambers, undergo 18 hours of incubation in a Cell Biology Experiment Facility or CBEF. Then the crewmembers activate the seeds with water or a saturated salt solution, followed by a second application of water 4 to 5 hours later. The crew harvests the cucumber seedlings and preserves them using fixation tubes called Kenney Space Center Fixation Tubes or KFTs, which then store in one of the station MELFI freezers to await return to Earth.

The results from HydroTropi, which returns to Earth on STS-133, will help investigators to better understand how plants grow and develop at a molecular level. The experiment will demonstrate a plant’s ability to change growth direction in response to gravity (gravitropism) vs. directional growth in response to water (hydrotropism). By looking at the reaction of the plants to the stimuli and the resulting response of differential auxin -- the compound regulating the growth of plants -- investigators will learn about plants inducible gene expression. In space, investigators hope HydroTropi will show them how to control directional root growth by using the hydrotropism stimulus; this knowledge may also lead to significant advancements in agriculture production on Earth."

When we talk about biofuels, it's often about the food - fuel conflict: the worry that growing plants for fuel comes at the expense of necessary food crops. Around the world, plant science researchers are trying to overcome this conflict, looking at the role of algae, of willows, and of perennial crops like Miscanthus.

A team of US researchers have a bigger hope - to find a source of biofuels which grows by feeding on polluted waters, cleaning up contamination as it grows. The potential plant biofuel is duckweed, a dull looking plant that spreads across ponds with incredible rapidity.

“You plant corn and get one crop a year,” says Dr. Jay Cheng, an associate professor in the Department of Biological and Agricultural Engineering at North Carolina State University. “We need to develop sources for fuel that are more renewable and won’t divert our nation’s food resources.”

Three-quarters of the mass of Cheng's duckweed is starchy content that can be broken down and fermented into ethanol. Because the duckweed can be harvested almost daily, it can produce four times the amount of ethanol per acre as corn, says his colleague Dr Anne-Marie Stomp, who previously modified the plant to produce proteins for pharmaceuticals.

They're now growing their duckweed on hog-waste lagoons - huge 'lakes' full of pig faeces and urine which are the result of factory pig farms. The hog-waste lagoons pollute the water and air around them, and may damage the health of people living nearby. It's a serious problem in the US, particularly in North Carolina and Iowa, which are the nation's biggest pig producers.

The duckweed consumes the excess nutrients from waste lagoons, cleaning the water as it grows. Farmers would need to be trained to grow and harvest duckweed, Stomp says, but the crop could produce jobs in rural North Carolina—as well as fuel and cleaner water.

The Nuffield Council on Bioethics has published its recommendations on ethical standards for biofuels, together with a collection of free teaching resources on the subject. 

Concerns over energy security, economic development and climate change are driving the development of biofuels. However, biofuels production, which currently mainly uses food crops, has been controversial because in some cases it has led to deforestation, and to disputes over rising food prices and land use.

New types of biofuels, such as those using non-food crops and algae, are being developed with the aim of meeting our energy demands whilst avoiding the problems of the past.

This report on the ethical implications of biofuels lays out 6 clear principals for future development to follow, and would make an interesting base for discussion in the classroom.

They recommend that:

• Biofuels development should not be at the expense of human rights
• Biofuels should be environmentally sustainable
• Biofuels should contribute to a reduction of greenhouse gas emissions
• Biofuels should adhere to fair trade principles
• Costs and benefits of biofuels should be distributed in an equitable way

Read the report

Teaching Resources

The Council has published a set of teaching resources for KS3 and above based on its 2011 report 'Biofuels: ethical issues'.

The resources are split into two lessons. In the first lesson, students will begin by learning about the different types of biofuels that are being produced as alternative renewable sources of energy. They will explore the advantages and disadvantages of these different types of biofuels, and begin to make comparisons. The second lesson includes a role-play exercise to aid further exploration of the impacts of biofuels production in countries such as Brazil, Malaysia and the USA.

Download the free resources.

2 June 2011

If you're sneezing away, your eyes are itching, and you're cursing plants and their pesky reproductive strategies that cause you horrible hayfever every year, then would you trust another plant to cure you?

At this time of year, we're all constantly inhaling the pollen that trees and plants are releasing into the air. Hayfever occurs when someone with a sensitized immune system inhales this pollen, and cells in the lining of the nose, mouth and eyes release histamine.This triggers the symptons of an allergic reaction, with the sneezing, the itchy eyes, and runny nose.

As sufferers will know, it can make spring and summer miserable, and make it hard to concentrate at school. The usual treatment is with anti-histamine drugs, but can a plant offer a solution?

The AoB blog reports on a new possibility, with a small perennial plant from northern Europe, Petasites hybridus (common butterbur).

"The usual treatment is with anti-histamine drugs, but a randomised, double-blind, placebo-controlled trial by Alina Dumitru et al. (Journal of Allergy and Clinical Immunology; doi:10.1016/j.jaci.2011.02.045) demonstrates that Ze 339 (petasol butenoate complex) – extracted from Petasites hybridus, a member of the Asteraceae – combats nasal mucosa swelling faster and more effectively. Furthermore, Ze 339 also appears to have a preventative effect."

Plant Conservation Day - May 18th - is a day to celebrate how far researchers, conservationists and botanic gardens worldwide have come in conserving endangered plants - and to take on new challenges for the future.

Teams in the UK are working to conserve plants from across the world, and from our own back garden. Although we often think about endangered species as living in the Amazon rainforest, or in wind-swept deserts, the truth is that there are plants in the UK every bit as rare as those across the world. The lady's slipper orchid is famously threatened, with only one flowering plant left in the wild, but there are plenty of less well known plants, like the fen orchid, which are dying out as their habitat is gradually eroded.The Sainsbury's Orchid Conservation Project, at Kew, for example, is working to grow native UK orchids in the greenhouse, and then transfer them out into the wild, to restock their populations. Dan Jenkins, now project manager for the Science and Plants for Schools team, started his working life in the Kew Micropropagation Labs, helping to conserve these threatened species.

It's not just botanic gardens who are working to conserve rare species of orchid - the pupils of Writhlington School in Radstock have developed a major conservation project and commercial enterprise from their School Greenhouse. Students raise thousands of orchid species from seed every year, in their own Micro-propagation laboratory, working to conserve species from Sikkim, Laos, Cape Town and Durban.

The same techniques of micropropagation that Kew have developed to preserve threatened plants have now been adapted so that you can use them in a school lab - and failing a supply of rare orchids, most schools recreate the technique with the rather less threatened cauliflower.

Try out the Kew Cauliflower Cloning protocol in your school.

11 May, 2011

Can evolutionary adaptations be reversed? It’s a question that’s intrigued scientists since the publication of The Origin of Species. In the late 19th century, paleontologist Louis Dollo argued that evolution could not retrace its steps to reverse complex adaptations — a hypothesis known as Dollo's law of irreversibility.

Teams investigating the hypothesis have found various parts of the jigsaw, but putting them together has proved difficult, especially as some seemed to conflict.

“In 2003, scientists showed that some species of insects have gained, lost and regained wings over millions of years. But a few years later, a different team found that a protein that helps control cells' stress responses could not evolve back to its original form,” summed up Anne Trafton of MIT.

Will altering the question get us somewhere closer to an answer? Jeff Gore, assistant professor of physics at MIT, says the critical question to ask is not whether evolution is reversible, but under what circumstances it could be. "It's known that evolution can be irreversible. And we know that it's possible to reverse evolution in some cases. So what you really want to know is: What fraction of the time is evolution reversible?" he says.

Hi and his students combined a computational model with experiments on the mutations in bacteria which confer resistance to certain key antibiotics. They found that “a very small percentage of evolutionary adaptations in a drug-resistance gene can be reversed, but only if the adaptations involve fewer than four discrete genetic mutations”.

Gore says his team's results offer support for Dollo's law, but with some qualifications.

"It's not that complex adaptations can never be reversed," he says. "It's that complex adaptations are harder to reverse, but in a sense that you can quantify."

The study may also go some way to explaining why humans still have an appendix, despite it being no longer needed. "You can only ever really think about evolution reversing itself if there is a cost associated with the adaptation," Gore says. "For example, with the appendix, it may just be that the cost is very small, in which case there's no selective pressure to get rid of it."

Read more on the MIT website