Parasitic plants – angiosperms that directly attach to another plant via a haustorium, a modified root that forms a morphological and physiological link between the parasite and host – tend to get a bad press. And it’s little surprise with the antics of such villains as Striga, the ‘violet vampire’, which greatly reduces the production of staple foods and commercial crops such as maize, sorghum, millet, rice, sugarcane and cowpea in many African countries, and can cause up to 100% crop loss. Slightly less devastating and livelihood-threatening is Rhinanthus minor – ‘yellow rattle’ – a hemiparasite on grasses, which is found in Europe, Russia, western Siberia, northern USA and Canada.

Whilst it is generally recognised that such plants have major negative impacts on plant community structure via influence on host productivity and competitive ability, James Fisher et al. show that nutrient-rich leaf litter from R. minor has a positive effect on plant community structure: ‘critically, in the case of grass and total community biomass, this partially negates biomass reductions caused directly by parasitism’. From sub-terranean to supra-terrestrial community impacts now, with another hemiparasite – mistletoes – and work by David Watson and Matthew Herring. Having already been established as ‘keystone resources’ – species providing important resources for a broad range of taxa and determining local diversities in these habitats – Watson and Herring experimentally investigated the role of Australian mistletoes such as Amyema miquelii (Loranthaceae, bog mistletoe) in eucalyptus woodland. After 3 years, sites from which mistletoe was removed lost, on average, a fifth of their total species’ richness, 26.5% of woodland-dependent bird species and more than one-third of their woodland-dependent residents.

The researchers, from The Institute for Land, Water and Society at Australia’s Charles Sturt University suggest that ‘nutrient enrichment via litter-fall is the main mechanism whereby the mistletoe promotes species’ richness, driving small-scale heterogeneity in productivity and food availability for woodland animals’. They further propose that this explanation applies to other parasitic plants with high turnover of enriched leaves, and that the community-scale influence of these plants is most apparent in low-productivity systems. I wonder if they had R. minor in mind? Prescience is, after all, a virtue…

[In the interests of fairness, it should be stated that Fisher et al. do cite Watson and Herring’s paper – Ed.]

Every so often there’ll be a news story like the massive decline in hedgehogs. The population is down by a third since the millennium. It’s obviously bad news but how much of a national priority should hedgehogs be? The Aspen hoverfly is down to 13 8 locations in Scotland. I can see this is a serious issue in terms of biodiversity, but again how much of a priority is one fly? But what if you could put all these stories together? What if it’s not just one species facing a crisis, but many? And what if they could be tackled by an integrated set of policies that don’t just protect hedgehogs or one fly, but a wide variety of species?

Today the State of Nature report is out, detailing the current challenges facing wildlife across the UK and its territories. You can download it for yourself from the RSPB’s site, and it’s an excellent read. It’s not just birds that are the focus of the report. A number of charities have got together to produce an expansive report including Plantlife.

The report tackles various habitats found around the UK, lowlands, forests, marine and so on. There are a few recurrent themes. Read more on “State of Nature report impresses. State of Nature itself does not.” »

Brunonia australis and Calandrinia sp. are Australian native herbs with commercial potential as flowering potted or bedding plants. Both species are best grown as annuals and flower naturally during spring and early summer. However, many ornamental plants are grown outside their natural flowering period to align flowering with peak market demand, which requires the capacity to predict flowering date under changing or different environments. Scheduling crop production using quantitative flowering time models can have considerable advantages as they can be tailored for individual requirements, unlike traditional scheduling methods that are typically based on calendar date and have no particular reference to the environment.

Most development rate models for ornamental species predict flowering time in relation to temperature, photoperiod and/or daily light integral as observed for the above models. However, there are few flowering time models for ornamental plants that include a vernalization function. Vernalization is important for early and complete flowering of many traditional herbaceous crops. Plant responses to vernalization have been incorporated into some models for field crops and arabidopsis, which reportedly improved accuracy. A new paper in Annals of Botany quantifies temperature and photoperiod or vernalization responses of B. australis and Calandrinia sp. and model development for the purpose of scheduling year-round flowering. The effects of temperature and photoperiod or vernalization on plant quality characteristics, including flower and branch number, were defined.

Modelling temperature, photoperiod and vernalization responses of Brunonia australis (Goodeniaceae) and Calandrinia sp. (Portulacaceae) to predict flowering time. Ann Bot (2013) 111 (4): 629-639.
doi: 10.1093/aob/mct028
Crop models for herbaceous ornamental species typically include functions for temperature and photoperiod responses, but very few incorporate vernalization, which is a requirement of many traditional crops. This study investigated the development of floriculture crop models, which describe temperature responses, plus photoperiod or vernalization requirements, using Australian native ephemerals Brunonia australis and Calandrinia sp.
A novel approach involved the use of a field crop modelling tool, DEVEL2. This optimization program estimates the parameters of selected functions within the development rate models using an iterative process that minimizes sum of squares residual between estimated and observed days for the phenological event. Parameter profiling and jack-knifing are included in DEVEL2 to remove bias from parameter estimates and introduce rigour into the parameter selection process.
Development rate of B. australis from planting to first visible floral bud (VFB) was predicted using a multiplicative approach with a curvilinear function to describe temperature responses and a broken linear function to explain photoperiod responses. A similar model was used to describe the development rate of Calandrinia sp., except the photoperiod function was replaced with an exponential vernalization function, which explained a facultative cold requirement and included a coefficient for determining the vernalization ceiling temperature. Temperature was the main environmental factor influencing development rate for VFB to anthesis of both species and was predicted using a linear model.
The phenology models for B. australis and Calandrinia sp. described development rate from planting to VFB and from VFB to anthesis in response to temperature and photoperiod or vernalization and may assist modelling efforts of other herbaceous ornamental plants. In addition to crop management, the vernalization function could be used to identify plant communities most at risk from predicted increases in temperature due to global warming.

AoB PLANTS is proud to have received endorsements from three distinguished scientists. Here’s what they had to say:

“PLOS is delighted that AoB PLANTS is bringing together leaders in the field to articulate an open access vision that is aligned with the future of scholarly communication.”
Cameron Neylon, PLOS Advocacy Director

“At this time of uncertainty in the future of scientific publications, AoB PLANTS is showing the path forward by combining open access with the long-term experience and reputation of Oxford University Press.”
Osvaldo E. Sala, Wrigley Chair & Foundation Professor, Arizona State University

“With broad coverage of the plant sciences and an intensifying focus on environmental biology, AoB PLANTS publishes articles of great interest and employs an open-access policy that ensures they are widely read.”
Daniel Simberloff, Nancy Gore Hunger Professor of Environmental Science, University of Tennessee

Robin Ince turned up at Ludlow on Friday as part of his tour The Importance of Being Interested. Ludlow, by and large, did not. It was Ludlow’s loss because they missed an entertaining evening.

If you’re not sure who he is, Robin Ince is the sane voice on the Infinite Monkey Cage, the BBC’s science/comedy show. When Brian Cox goes off on one of his surreal rants about Physics being the best science* it’s Robin Ince who pulls him back to reality. A person looking at things sensibly doesn’t sound like the basis for good comedy but, a bit like Douglas Adams, Robin Ince is a normal person in a bizarre world.
Read more on “Robin Ince – The Importance of Being Interested (at Ludlow)” »

Understanding the production of L-ascorbic acid (L-AsA), its cellular roles and its accumulation in fruit has advanced considerably over the last decade. The importance of irradiance on fruit relative to leaves, in tomato, suggests that there is little linkage between leaves and fruits in the supply of L-AsA. While manipulation of kiwi vine temperature supports fruit-based production, others have observed variability in long-distance phloem L-AsA transport from leaves to developing fruit. In apple, fruit L-AsA concentration is dependent on production which declines with maturation, despite L-AsA accumulating with increasing fruit weight. Tomatoes show pectin polymer degradation as a source of precursors for L-AsA synthesis and accumulation via L-galactonic acid. What is clear are species differences in the mechanism by which total fruit L-AsA production is modulated during development; in some fruits, e.g. strawberry, melon and tomato, it remains constant while in others, e.g. apple and orange, it declines). An explanation of how total fruit L-AsA is modulated during fruit development may differ with species. L-AsA is detected in leaf phloem, but what remains unclear is what contribution long-distance transport from potential sources, such as leaves, makes to the pattern and amount of AsA that accumulates in fruit tissues at maturity.

A new paper in Annals of Botany aims to determine the role of green leafy tissues in the development and growth of fruits and how these processes influence L-AsA production and accumulation in fruit. It uses black currants (Ribes nigrum) as a model plant because its fruit have high L-AsA concentrations and there is some knowledge of the pattern of biosynthesis and accumulation of L-AsA over time. What remains unclear is the location of fruit L-AsA synthesis and under what circumstances, if any, does fruit growth compete with L-AsA production.

Linking ascorbic acid production in Ribes nigrum with fruit development and changes in sources and sinks. (2013) Ann Bot 111 (4): 703-712. doi: 10.1093/aob/mct026
Understanding the synthesis of ascorbic acid (L-AsA) in green tissues in model species has advanced considerably; here we focus on its production and accumulation in fruit. In particular, our aim is to understand the links between organs which may be sources of L-AsA (leaves) and those which accumulate it (fruits). The work presented here tests the idea that changes in leaf and fruit number influence the accumulation of L-AsA. The aim was to understand the importance of leaf tissue in the production of L-AsA and to determine how this might provide routes for the manipulation of fruit tissue L-AsA.
The experiments used Ribes nigrum (blackcurrant), predominantly in field experiments, where the source–sink relationship was manipulated to alter potential leaf L-AsA production and fruit growth and accumulation of L-AsA. These manipulations included reductions in reproductive capacity, by raceme removal, and the availability of assimilates by leaf removal and branch phloem girdling. Natural variation in fruit growth and fruit abscission is also described as this influences subsequent experimental design and the interpretation of L-AsA data.
Results show that fruit L-AsA concentration is conserved but total yield of L-AsA per plant is dependent on a number of innate factors many of which relate to raceme attributes. Leaf removal and phloem girdling reduced fruit weight, and a combination of both reduced fruit yields further. It appears that around 50% of assimilates utilized for fruit growth came from apical leaves, while between 20 and 30% came from raceme leaves, with the remainder from ‘storage’.
Despite being able to manipulate leaf area and therefore assimilate availability and stored carbohydrates, along with fruit yields, rarely were effects on fruit L-AsA concentration seen, indicating fruit L-AsA production in Ribes was not directly coupled to assimilate supply. There was no supporting evidence that L-AsA production occurred predominantly in green leaf tissue followed by its transfer to developing fruits. It is concluded that L-AsA production occurs predominantly in the fruit of Ribes nigrum.

LANDSAT and the power of Google allow us to see the planet age before our eyes. See the desert bloom and the forest decay. This post is in French with an English version below it.

Le programme LANDSAT a été créé par la NASA au milieu des années 60 à des fins civiles d’observation de notre planète. Sept satellites ont été lancés entre 1972 et 1999 et un huitième doit l’être en 2013. Des millions d’images ont pu être capturées par ses instruments, pour des visées scientifiques ou économiques d’observations de l’agriculture ou encore du changement climatique.^[1] Ces satellites photographient tous les 16 jours l’intégralité de la planète depuis 41 ans et ont été les témoins privilégiés de bien des changements à la surface de notre bonne vieille planète.

Le projet TIMELAPSE, créé par Google, a permis d’agréger les photos prises depuis 30 ans en différents points de la planète pour présenter des cartes interactives, saisissantes par les transformations qu’elles présentent. Celles-ci sont co-publiées sur le site du géant de l’internet et par le prestigieux magazine TIME.^[2]&[3]

En plus de leur beauté, ces cartes nous amènent à réfléchir sur l’impact de l’Homme sur sa planète et son milieu de vie, sans cesse en accélération. On peut par exemple y voir verdir le désert Saoudien devant nos yeux ébahis, ou constater notre impuissance face à la déforestation galopante en Amazonie.^[2]&[4]

Read more on “La Terre, elle aussi, vieillit ! / The Earth is growing old too!” »