Monthly Archives: February 2012

Root traits and decomposition rates

Root traits and decomposition rates

Root traits and decomposition rates

Fine-root decomposition is an important determinant of nutrient and carbon cycling in grasslands, but little is known about the factors controlling interspecific root decomposition. By studying 18 Mediterranean herbaceous species from different life histories and taxonomic groups, Birouste et al. demonstrate that the potential decomposition rate of fine roots is affected by root chemical composition but not by morphological traits. Patterns of root traits, including decomposition rate, mirror those of leaves, resulting in a similar clustering of species.

Model of myxospermous seed-mucilage expansion

Model of myxospermous seed-mucilage expansion

Model of myxospermous seed-mucilage expansion

Myxospermy, the ability of a seed to produce mucilage upon hydration, is reported to provide important functional advantages to various aspects of seed ecology. Using data gathered from the myxospermous seeds of shepherd’s purse, Capsella bursa-pastoris, Deng et al. parameterize the volume and weight of the mucilage before and after expansion. They find that expansion occurs as a function of water uptake and polymer-chain relaxation, and the data are used to develop a diffusion-based mathematical model of seed-mucilage expansion, which may be applied to assess seed-mucilage–soil interactions.

Manioc marriage mystery unearthed

Image: Wikimedia Commons.

Image: Wikimedia Commons.

Echoing Forrest Gump’s famous box of chocolates quote (number 40 in the American Film Institute’s Top 100 movie quotes), you never really know what to expect when you get married. Well, certainly in some parts of Africa you may get more than you bargained for!

Investigating marriage practices in small African farming communities in Gabon, Marc Delêtre and colleagues discovered a remarkable connection with the genetic diversity of manioc, which clustered and was lowest in the north and highest in the south of the region. Manioc – probably better known as cassava (Manihot esculenta) in Europe – is native to South America, but is extensively cultivated as an annual crop in tropical and subtropical regions for its edible starchy, tuberous root, a major source of carbohydrates.

In the rather technical language of the abstract, ‘spatially explicit Bayesian clustering methods showed that geographical discontinuities of manioc genetic diversity mirror major ethnolinguistic boundaries, with a southern matrilineal domain characterized by high levels of varietal diversity and a northern patrilineal domain characterized by low varietal diversity’. Alternatively, in the more accesible language of a press release: in the south of the region, a bride brings to her husband’s village manioc varieties from her mother’s farm; in the north, new brides turn up manioc-free and rely on gifts of manioc varieties from their mother-in-law. All of which manioc mayhem of mixing-and-matching provides an important – if maybe unexpected – human dimension to geographical patterns of crop diversity. However, one is left wondering on what basis men in those regions choose their wives: is the manioc – and the future family’s food security – more important, or is a cheerful disposition, etc, more sought after?

Although a staple crop for approx. 250 million sub-Saharans, cassava is notoriously poor in protein – a cassava-based diet provides less than 30% of the minimum daily requirement for protein – and contains compounds that release hydrogen cyanide (which is poisonous!). Welcome news, indeed, then, that Narayanan Narayanan et al. at the Donald Danforth Plant Science Center (St. Louis, USA) have delivered a ‘double-whammy’ to cassava research, which not only reduces cyanogen content, but also increases protein levels. Using a GM approach they created plants that over-express hydroxynitrile lyase (HNL), which accelerates production and hence also loss of HCN during food processing, and – because the HNL is located in the cell walls, which survive the processing – leads to an increase in protein content of the foodstuff! How cool is that! And yes, there’s even more good news on the cassava front. Nearly US$12 million – from the Bill & Melinda Gates Foundation, The Monsanto Fund and the Howard Buffett Foundation – has been provided to VIRCA (the Virus Resistant Cassava for Africa project). The hope is to generate cassava resistant to such viruses as CBSD (cassava brown streak disease) and CMD (cassava mosaic disease), which are causing major, devastating losses to cassava crops in Uganda and Kenya; indeed, CBSD is listed as one of the seven most dangerous plant diseases in the world for the impact it can have on food and economic security across Africa. And news that will be boosted by the announcement that BGI (formerly the Beijing Genomics Institute) will ‘work with Colombia’s International Center for Tropical Agriculture (CIAT) to sequence 5,000 cassava genotypes in a project that will aid scientists as they improve the crop through genetic engineering’. Which itself is on the back of the first draft of the cassava genome published in late 2009. Yes, 2011 has been a good year for manioc/cassava/yuca/mogo aspirations – let’s hope 2012 is even better because 500 million people worldwide are relying upon it!

PHAN and compound leaf morphology

PHAN and compound leaf morphology

PHAN and compound leaf morphology

For both simple and compound leaves, a MYB domain transcription factor PHANTASTICA (PHAN) plays an important role in establishing the adaxial domain in the leaf. Zoulias et al. generate and analyse transgenic tomato plants expressing tomato PHAN (SlPHAN) and tobacco plants that over-express tomato SlPHAN. Modulations in SlPHAN resulted in a variety of leaf morphologies, and the results suggest that SlPHAN plays a role in medio-lateral extension of the adaxial domain and contributes to final leaf morphology in tomato.

New taxonomy of Brachypodium distachyon

New taxonomy of Brachypodium distachyon

New taxonomy of Brachypodium distachyon

The model grass species Brachypodium distachyon has three cytotypes that are currently regarded as part of a single species. Catalán et al. combine analysis of phenotypic traits with multiple cytogenetic analyses and detect significant differences between the cytotypes and demonstrate stability of characters in natural populations. Genome size estimations, GISH, FISH and CCP confirm that the 2n = 10 and 2n = 20 cytotypes represent two different diploid taxa, whereas the 2n = 30 cytotype represents a derived allotetraploid from them. They keep the name B. distachyon for the 2n = 10 cytotype, and describe two novel species as B. stacei for the 2n = 20 and B. hybridum for the 2n = 30 cytotypes.

Passerine pollination in a winter-flowering tree

Passerine pollination in a winter-flowering tree

Passerine pollination in a winter-flowering tree

Birds can be alternative pollinators for winter-flowering plants outside the tropics where low temperatures limit insect activity. Feng et al. observe pollinator visitation to loquat (Eriobotrya japonica, Rosaceae) and exclude birds and other animals from the flowers. They determine that in late winter two passerine birds (Pycnonotus sinensis and Zosterops japonicus) are effective pollinators, and that the perigynous flowers reward passerines with relatively large volumes of dilute nectar. The results suggest a possible association between perigyny and bird pollination.

Ontogeny constrains sprouting in Quercus

Ontogeny constrains sprouting in Quercus

Ontogeny constrains sprouting in Quercus

Evidence suggest that suppressed bud burst and thus epicormic shoot emergence (sprouting) are controlled by water–carbohydrate supplies to entire trees and buds. Morisset et al. study stand water status and carbohydrate distribution in dominant trees of sessile oak, Quercus petraea, and find that sprouting is more intense in parts of the stand free from accompanying vegetation and on upper trunk segments. The more epicormics that a trunk segment bears, the more chances it had to bear sprouts, and the results thus infer water–carbohydrate control and show direct evidence of constraints by epicormic ontogeny.

Progenitor–derivative speciation in Pozoa

Progenitor–derivative speciation in Pozoa

Progenitor–derivative speciation in Pozoa

Progenitor–derivative speciation occurs when an isolated peripheral population diverges from the ancestral condition and forms a derivative species. López et al. find evidence of this type of speciation in the genus Pozoa (Apiaceae), consisting of two species endemic to the southern Andes. Pozoa volcanica appears to have derived recently from the progenitor, P. coriacea, as evidenced by the former’s reduced genetic variability (determined using AFLP analysis), narrow geographic distribution and restricted range of ecological tolerance.

Phenology and resource allocation in Ruellia

Phenology and resource allocation in Ruellia

Phenology and resource allocation in Ruellia

In plants that produce both closed, obligatory self-pollinated (cleistogamous) and open, potentially out-crossed (chasmogamous) flowers, suboptimal conditions typically favour production of cleistogamous flowers. Munguía-Rosas et al. study the effects of shade and drought on Ruellia nudiflora and find that cleistogamous flowers are produced earlier under shaded conditions whilst chasmogamous flowers are produced for shorter periods; however, resources are preferentially allocated to those chasmogamous flowers receiving larger pollen loads. The results demonstrate complex interactions between environment and reproduction in cleistogamous plants.

Embrace Wikipedia!(?)

Wikipedia

Wikipedia

Now that’s probably something you thought you would never hear an academic say. Well, let’s qualify that outrageous statement. Acknowledging that entries on Wikipedia (http://www.wikipedia.org/) can be amended by anybody who has access to the internet – whether they have, or have not, an axe to grind – we rightly caution our students that Wikipedia is best used as a starting point for more serious academic literature enquiry elsewhere (preferably to rigorously peer-reviewed items in reputable journals, such as the Annals of Botany). However, in an Opinion piece at SciDev.Net (the Science and Development Network, a not-for-profit organisation dedicated to providing reliable and authoritative information about science and technology for the developing world), Samuel Assefa and Alex Bateman argue for greater use of Wikipedia to fill a resource gap for today’s ‘high-tech’ generation of students, policymakers and the public in poor countries. Which argues for closer control over the veracity of what is entered onto Wikipedia, especially if it is used to give policymakers a better understanding of science, which is sorely needed according to a report for the Parliament of Uganda and discussed in a SciDev.Net Editorial by David Dickson. But rather than rely on the self-policing of posted material by responsible Wiki contributors, maybe this argues more compellingly for a widening of the availability of peer-reviewed Open Access (OA) scientific literature, as argued by Leslie Chan. Whilst the ‘developed world’ may be awash with journal access, the developing world is generally not so well served by traditional research publishing, so it is hoped that OA can here make the difference that is required to bring much-needed knowledge to the masses, for the greater good. Fortunately, there are initiatives that aim to do just that, as outlined by BioMed Central’s Head of Public Relations, Matthew McKay. But such ambitious projects need global co-operation to succeed, so it is good to see endorsement by UNESCO (the United Nations’ Educational, Scientific and Cultural Organization), which works to create the conditions for dialogue among civilizations, cultures and peoples, based upon respect for commonly shared values. Accordingly, UNESCO both promotes and supports Open Access via its Global Open Access Portal. Good news also that – according to ‘a source at BMC Central’ – the UK government is keen to widen OA access in its new innovation and research strategy (see especially pp. 76–77) for growth (for the UK…). However, is there not a danger of applying double standards here? On the one hand we say that Wikipedia is ‘not good’ for students in the developed world, but on the other hand we sanction its use in the developing world. If we are equal-handed and argue just for Wikipedia to be used in both as a starting point, then the developing word still has the problem of limited access to scientific literature, which is back to the OA issue again. So, until proper OA is more widely available for all, perhaps Wikipedia – for better or worse – is the new Global Open Access.