Tag Archives: Plant Science

Clean drinking water via plants

Xylem structure Effective devices for providing safe drinking water are urgently needed to reduce the global burden of waterborne disease. A recent paper in PLoS ONE shows that plant xylem from the sapwood of coniferous trees – a readily available, inexpensive, biodegradable, and disposable material – can remove bacteria from water by simple pressure-driven filtration. Approximately 3 cm3 of sapwood can filter water at the rate of several liters per day, sufficient to meet the clean drinking water needs of one person. The results demonstrate the potential of plant xylem to address the need for pathogen-free drinking water in developing countries and resource-limited settings.

Since angiosperms (flowering plants, including hardwood trees) have larger xylem vessels that are more effective at conducting sap, xylem tissue constitutes a smaller fraction of the cross-section area of their trunks or branches, which is not ideal in the context of filtration. The long length of their xylem vessels also implies that a large thickness (centimeters to meters) of xylem tissue will be required to achieve any filtration effect at all – filters that are thinner than the average vessel length will just allow water to flow through the vessels without filtering it through pit membranes. In contrast, gymnosperms (conifers, including softwood trees) have short tracheids that would force water to flow through pit membranes even for small thicknesses (<1 cm) of xylem tissue. Since tracheids have smaller diameters and are shorter, they offer higher resistance to flow, but typically a greater fraction of the stem cross-section area is devoted to conducting xylem tissue. For example, in the pine branch used in this study, fluid-conducting xylem constitutes the majority of the cross-section. This reasoning leads the authors to the conclusion that in general the xylem tissue of coniferous trees – i.e. the sapwood – is likely to be the most suitable xylem tissue for construction of a water filtration device, at least for filtration of bacteria, protozoa, and other pathogens on the micron or larger scale.

Boutilier MSH, Lee J, Chambers V, Venkatesh V, Karnik R (2014) Water Filtration Using Plant Xylem. PLoS ONE 9(2): e89934. doi:10.1371/journal.pone.0089934

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Science: for the sheer fun of it!

Image: Robert Hooke, 1665. Micrographia. Jo. Martyn and Ja. Allestry, London.

Image: Robert Hooke, 1665. Micrographia. Jo. Martyn and Ja. Allestry, London.

Despite frequently expressed assumptions to the contrary, science – whether it’s botany or some lesser intellectual pursuit – isn’t always about having an idea and undertaking an experiment to test it. Anyway, that type of investigation can be hard work. Fortunately, there is an alternative approach that basically studies ‘what’s there’ and muses on why that might be (or not…), so-called blue skies research.  Sadly, the latter type of science – which I think is much more fun and interesting – is less likely to get financed than the ‘there’s a definite question that we aim to answer’ type of study, and is generally much less common. Nice then to see that, in conversation with Sarah Williams in the Howard Hughes’ Medical Institute’s Fall 2013 issue of the HHMI BulletinDr Richard Flavell (Sterling Professor of Immunobiology at Yale School of Medicine) promotes the view that observation-driven studies have a place in science. He goes further in saying that, ‘there’s nothing wrong with a lab team doing observational study after observational study. They are still helping advance the science, and likely providing fodder for hypothesis-driven studies to come…’. Now that is my kind of science. I do hope those who fund research are listening to – and heeding – this!

Unfortunately, I suspect the more usual reaction to requests to finance such work from the grant-awarding bodies would be similar to that which prompted this acknowledgement in a scientific paper: ‘I thank the National Science Foundation for regularly rejecting my (honest) grant applications for work on real organisms (cf. Szent-Gyorgyi, 1972)…’ (from Leigh Van Valen’s* paper, ‘A new Evolutionary Law’). But occasionally studies along the lines of ‘let’s just see what turns up’ do appear. Take, for example, Michael Proctor and Margaret Bradshaw’s first in a planned series of papers on scanning electron microscopy (SEM) examination of leaves of British sedges in New Journal of Botany**. Acknowledging that the ability to identify sedges in the field is important to many vegetation studies but recognising that inflorescences are available for only a short period each year, the pair have concentrated on SEM studies of leaf surfaces to assist those identification endeavours. Whilst the duo don’t advocate taking a SEM into the field, they do believe that such SEM studies will be ‘useful in putting leaf characters on a firmer footing, and drawing attention to characters which could be useful for identification with a hand-lens or low power microscope’ (which can be taken into the field…). The images need to be seen to be properly appreciated, but the imaging of epicuticular waxes in, for example, Figure 1f attests to their high quality. Bring on Part 2!

[For those expecting to read about ‘botanist’ Richard Flavell PhD, FRS, CBE, former Director of the John Innes Centre, etc, I’m sorry to ‘disappoint’ – Ed.]

* Leigh van Valen is an American evolutionary biologist probably best known for the Red Queen Hypothesis.

** this is the official organ of the BSBI,  the leading society in Britain and Ireland for the study of plant distribution and taxonomy. The Botanical Society of Britain and Ireland was formerly called the Botanical Society of the British Isles, and represents a name change every bit as slick as that of the WWF (which changed from World Wildlife Fund to World Wide Fund for Nature in 1986), and which also allows it to keep its abbreviation of BSBI (which is an initialism not an acronym) the same. The New Journal of Botany is itself the successor to the BSBI’s Watsonia journal, named in honour of Hewett Cottrell Watson (one of the “most colourful figures in the annals of British botany”) who developed the vice-county system in 1852 that currently divides up the United Kingdom and the Republic of Ireland into 152 geographical units for vegetation recording purposes.]

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You can’t be best at everything…

Image: Wikimedia Commons.

Image: Wikimedia Commons.

There is a widespread belief that everything in/of/from/about America is bigger, better, faster, etc, than anything from elsewhere in the world. That is probably the best example of spin over substance ever foisted on an unsuspecting world, and is a true testament to the power of marketing and public relations.

Take, for example, the arresting title ‘This Could Be the Oldest Flowering Plant Ever Found in North America’. So prevalent is that view of American supremacy and so conditioned are we to its acceptance that many of us will have read that text and mentally added a comma after the words ‘ever found’ (and the importance of comma placement is legendary).  The news story concerns a re-assessment of fossil plants stored away in the USA’s Smithsonian National Museum of Natural History.  Originally thought to be a fern, reinspection and analysis by USA-based Nathan Jud and Leo Hickey now confirms that the fossil is an angiosperm (a flowering plant) between 125 and 115 million years old (Ma) – the Lower Cretaceous – named Potomacapnos apeleutheron.

While this is amongst the oldest flowering plants found in America, it is not the oldest known on Earth. That honour goes – currently! – to the unnamed bearers of ‘angiosperm-like pollen’ and the described genus Afropollis from Middle Triassic deposits in Switzerland that are 247.2–242.0 Ma, as unearthed by Peter Hochuli and Susanne Feist-Burkhardt. The pollen was studied using confocal laser scanning microscopy (CLSM), exploiting the autofluorescence still present in such ancient organic-walled microfossils. Quite dramatically, this announcement pushes back the origin of flowering plants another 100 Ma into history, which must be rather gratifying for the Swiss–German team. So, whilst national self-belief is a good thing to have (rather like patriotism),  it mustn’t blind us to the fact that other countries may have more legitimate claims to ‘biggest and best’ (and which might stray into nationalism). And anyway, it’s only because of ‘accidents of history, geography and politics’ that scientific discoveries are tied to a particular place and claimed for, and/or by, individual countries. Science – and its discoveries – belongs to us all. There, I’ve said it (and with flowers…).

[As usual, Mr Cuttings has tried to be a little mischievous in this item. But it probably won’t halt the activities of those whose lifelong goal is to seek out the biggest, best, etc, so expect further archaefloral revelations from the good old US of A in due course (and maybe further afield…), as more store-rooms replete with rocky riches are rummaged through, re-examined, and re-assessed! And if a good bit of healthy, old-fashioned competition and rivalry can spur on all those engaged in the process of science to even greater things, then so much the better – for us all! – Ed.]

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Plant science and the gluten-free diet

AoB Blog welcomes the return of guest author, Charlie Haynes, who is currently a final year student in the School of Biological Sciences at the University of Leicester.

Gluten free For around ten thousand years cereals have been a staple component of human diets. They are ubiquitous, with a cultural and religious significance to many. They permeate our diet. But the component that makes wheat so perfect for making bread dough, with its stretchy, elastic consistency, can also elict a severe autoimmune response for sufferers of coeliac disease.

Gluten proteins split into two subgroups; gliadin (soluble) and glutenin (insoluble), with gliadin proteins contributing the majority of epitopes associated with coeliac disease. The autoimmune reaction results in inflammation of the small bowel resulting in a damaging of the gut lining and vitamin malabsorption. Untreated it can lead to a quadrupling in mortality. And there has been a dramatic increase in prevalence of undiagnosed coeliac disease, with around 1 in 100 people in the UK now affected.

The only current treatment for coeliac disease is strict adherence to a gluten-free diet which is tricky. Gluten permeates the western diet, and there is evidence to suggest that a gluten free diet isn’t the shining beacon of health purported by health magazines. It can be high in fat, and deficient in iron, folate and calcium. Once patients are on a gluten free diet they often put on weight.

But not all gluten proteins contain the allergenic stimulatory epitopes. Various groups have been trying to decrease these epitopes whilst maintaining the technical properties important in bread making. Broeck et al investigated the effect of deleting individual gene loci in Triticum aestivum or chinese spring, the first wheat variety to have its genome sequenced. They were able to identify the specific gliadins that could remove stimulatory epitopes whilst maintaining structural properties (the ω-gliadin, γ-gliadin, and LMW-GS loci from the short arm of chromosome 1 of the D-genome, 1DS).

Barro et al were able to go further using RNA interference (a method of using RNA to prevent gene expression by destroying specific mRNA sequences) to down regulate expression of these gliadins. Gluten extracts from three of these transgenic lines samples were unable to elicit T cell responses and six others caused reduced responses.

This is groundbreaking work for coeliac patients. It means that we are coming closer to being able to marginalise the effect of coeliac disease in the day to day life of sufferers. Being able to have coeliac specialised wheat without any loss of technical properties will make it much easier for sufferers to enjoy more foods, and live more fulfilled, healthier lives.

 

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Celebrating basic plant science

Image: Alberto Salguero/Wikimedia Commons.

Image: Alberto Salguero/Wikimedia Commons.

In case you missed this, here’s news of a charming series that aims to present vignettes of current plant science research and researchers within a broader educational remit of promoting the importance of basic plant science. As such it could be useful for impressing upon those supposedly impressionable early-stage undergraduates the relevance of phytology, and might also have a role to play in wider outreach evangelising of the importance of plant biology. Anyway, this first – of many? – in the series showcases the work of Siobhan Braybrook, Career Development Fellow at the University of Cambridge’s Sainsbury Laboratory. Penned by Siobhan, it explains her fundamental work on aspects of plant development – including the important role of pectin in determining cell wall expansion – and discusses why such basic plant science is value for money. A little gem from GARNet (a sponsored network that supports arabidopsis researchers and the wider plant community).
[GARnet is in turn sponsored by the BBSRC (Biotechnology and Biological Sciences Research Council), a major UK government-funded sponsor of biological research. Another ‘importance of basic plant science’ item you might be interested in is the University of Cambridge’s Professor David Baulcombe’s keynote talk from the UK PlantSci 2013 meeting.

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The Annals measures up…

Image: Wikimedia Commons.

Image: Wikimedia Commons.

Although much-derided, publication metrics – such as journal Impact Factorsseem to rule career advancement and progress in academia world-wide. The plant sciences are no exception with regard to this over-hyped, inappropriately used, arbitrary method of assessment. Well, we would say that if we were doing badly as a result of this system. However, a reason to be cheerful is that the Annals of Botany is amongst the ten ‘Top publications’ in botany/plant science (and one of only two with botany in its title!). This list – produced by Google Scholar Metrics – provides an ‘easy way for authors to quickly gauge the visibility and influence of recent articles in scholarly publications’, and uses so-called ‘h’ metrics. Publications are ordered by their five-year h-index and h-median metrics, and are searchable – for example, to see which articles in a publication were cited the most and who cited them. Now, although the dates and citation counts used are estimated(!), they are determined automatically by a computer program, and must therefore be independent, objective and believable. So, good news for the journal (yay!), and – maybe more importantly(?) – for those who publish in it!

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Effects of density and fire on the vital rates and population growth of a perennial goldenaster

Gornish

Image of Pityopsis aspera. Taken by E. S. Gornish.

In a novel analysis by Gornish published in AoB PLANTS, a regression-design life-table response experiment was used to determine how the interaction of fire and density affected vital rates of the perennial composite Pityopsis aspera, and ultimately how these changes in vital rates contributed to differences in estimated population growth rates. The shape of the relationship between population growth rate (λ) and density was modified by fire, primarily as a result of contributions from adult flowering stasis and survival, and first-year survival probabilities. Fire modified and even reversed the effect of extreme densities on adult flowering stasis and survival and of first-year survival, resulting in more positive contributions from these transitions to λ at the lowest and highest density values. These results demonstrate the first application of a regression-design life-table response experiment to elucidating the interactive effects of density and fire. They highlight the utility of this approach for both capturing the complex dynamics of populations and establishing a means of determining how vital rates might contribute to differences in demography across densities.

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