Heterodichogamy and thrips-pollination in Platycarya strobilacea

Heterodichogamy and thrips-pollination in Platycarya strobilacea

Heterodichogamy and thrips-pollination in Platycarya strobilacea

Heterodichogamy, a dimorphism in which two morphs coexist in a population and undergo synchronous reciprocal sex changes, is an extremely rare and poorly understood sexual system. Fukuhara and Tokumaru study Platycarya strobilacea (Juglandaceae) and demonstrate that it is heterodichogamous based on observations of inflorescence architecture, sexual expression and pollination biology. Pollination by thrips is suggested by their frequent presence with attached pollen grains, the scarcity of other insect visitors, the synchronicity of thrips number in male spikes with the maturation of female flowers, and the morphological characters shared with previously reported thrips-pollinated plants.

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Summer* Reading

*Or winter reading for our followers in the better hemisphere.

In the northern hemisphere, the summer break is upon us. If you’re looking for some light reading to take with you on holiday, what would you recommend? Kirkus Reviews has a short article on recent ecological science fiction, Seeders by A.J. Colucci looks like it could be interesting, combining plant neurobiology with horror. io9 has their own list from 2011, which includes a few I haven’t read as does SF Signal from 2012. Alan Cann has read The Windup Girl by Paolo Bacigalupi, which I realise is another book I haven’t read.

Is there a science fiction book you’d recommend that tackles plants in a credible way?

If you prefer your SF to feel like work, then you’re not limited just to moving from science to fiction. Recently a few have tried going the other way in the Science of Tatooine Blog Carnival. Matt Shipman explains Why a Bunch of Science Writers Are Writing About a Fictional Planet, including Malcolm Campbell’s speculative Tatooine’s tangled bank – plants evolve in a galaxy far, far away

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So what ARE the 7 most important plants?

A while back Annals Editor Pat Heslop-Harrison was asking what ten plants should botanists know about. I’ve taken it a bit further with a Buzzfeed post on the 7 Plants That Changed Your Life.

I’ve tried to pick seven plants with global consequences, but I’m not entirely happy with the list. The seven plant limit means I’ve missed out a lot of important plants. For example, there are no marine plants on the list. Nothing that really address important evolutionary steps that plants made, so no mosses or ferns,

So what plants would you add to the list and why? I’d be interested to see if our readers could compile another list of another seven plants that would be equally good, or better.

Leave your suggestions below, or at Buzzfeed or on our Facebook page.

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Clonal growth in the absence of a mating morph

Nymphoides montana

Nymphoides montana. Photo: Ian Sutton/Flickr.

Many aquatic species with stylar polymorphisms have the capacity for clonal and sexual reproduction. Haddadchi et al. study differences between a monomorphic population of Nymphoides montana and polymorphic populations. They find that very few seeds are produced in the monomorphic population due to dysfunctional pollen and ovules, and that stigma–anther separation is minimal. ISSR results show that the monomorphic population is one large, single-ramet genotype, unlike the multi-genotypic fertile polymorphic populations. Evolutionary loss of sex in a clonal population in which a mating morph is absent is evident, and under these conditions clonal growth may assure reproduction and expand the population via spreading stolons.

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An explosive mix: C4, C3, C2 and CCM

Image: Ninghui Shi/Wikimedia Commons.

Image: Ninghui Shi/Wikimedia Commons.

As if the task of explaining the details of the ‘normal’ C3 Calvin Cycle of photosynthesis (P/S) to our students isn’t hard enough, we also need to appraise them of C4 P/S  – with its spatial separation of initial CO2 fixation into organic acids in mesophyll cells and its subsequent release and re-fixation via the enzyme Rubisco (ribulose-1,5-bisphosphate carboxylase/oxygenase)  into the photosynthetic Calvin Cycle proper within bundle sheath cells*. As testing and trying as that is, nature always has to go one ‘better’, and ‘spoil’ things. So, the fin-de-millennial recognition of a variant of this C4 P/S in which initial CO2 fixation into 4-carbon acids and its subsequent release and re-fixation into the Calvin Cycle of C3 P/S takes place within a single cell is kind of unwelcome (no matter how fascinating it is!). Well, anyway, it exists – in such higher plants as Suaeda (Borszczowia) aralocaspica, Bienertia cycloptera, B. sinuspersici and B. kavirense, all in the Chenopodiaceae (now within the Amaranthaceae) – so we need to get over it, and try and understand it. And that’s what Samantha Stutz et al. have been doing. Although these plants perform spatial separation of the two CO2 fixation events within a single mesophyll cell, they do so using two distinct – dimorphic – chloroplasts. Already known is that light is necessary for development of the dimorphic chloroplasts in cotyledons in B. aralocaspica. In the dark they only have a single structural plastid type (which expresses Rubisco): light induces formation of dimorphic chloroplasts from the single plastid pool, and structural polarization leads to the single-cell C4 syndrome. The aim of Stutz et al.’s study was to determine how growth under limited light affects leaf structure, biochemistry and efficiency of the single-cell CO2-concentrating mechanism. Overall, the team found that the fully developed single-cell C4 system in B. sinuspersici is robust when grown under ‘moderate light’. Where might this sort of work be going? Well, whilst it is interesting for its own sake – the pure pursuit of knowledge – it has a more applied dimension too. Central to all of this single-cell photosynthetic biology and biochemistry is the concept of CCM, carbon-concentrating mechanisms, whereby levels of CO2 are increased in the vicinity of Rubisco so that it favours photosynthesis – CO2-fixation – over photorespiration (so-called C2 photosynthesis) which uses O2 as substrate and consequently reduces photosynthetic efficiency. Well, in bids to replicate some of the greater photosynthetic efficiency of C4 plants (largely by virtue of their diverse CCMs…), an attractive notion is to engineer various forms of CCM into C3 crop plants. This approach is exemplified in the work of Mitsue Miyao et al., where they attempted to exploit enzymes of the facultative C4 aquatic plant Hydrilla verticillata (which engages in single-cell C4 P/S) to convert rice from its typical C3 P/S into a single-cell C4 photosynthesiser. Although they didn’t achieve their goal (and it’s good to know that ‘negative’ results can still be published!), their article is an interesting and soul-bearing account of the lessons learned in this work. As we continue our quest for that elusive boost in photosynthetic yield, we’ll no doubt continue to exploit any biochemical variant on the photosynthetic theme that nature displays. Which begs the question: how many more variants exist amongst the 325,000 species of flowering plants (let alone all the algae and other members of the plant kingdom)? Seems like we need more plant anatomists, plant biochemists, plant physiologists – as well as plant taxonomists (see my last post on this blog) – after all!

 

* That’s C4 P/S as opposed to CAM (Crassulacean acid metabolism), which is also a version of C4 P/S but which involves temporal separation of the same two carbon-fixation events in plants such as pineapple, cacti and agave. However, CAM is hardly ever referred to as C4 P/S because the all-powerful Zea Supremacy lobby has commandeered the term for that spatially separated C4 version found in plants such as maize… but don’t get me started on that!

 

[Intriguingly, and in addition to its dimorphic chloroplasts, Suaeda aralocaspica has dimorphic seeds, which exhibit distinct differences in dormancy and germination characteristics. Now, they say that things come in threes, so what’s the third dimorphy about this iconic species…? – Ed.]

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Limited plasticity in functional root traits of maple and oak

Limited plasticity in functional root traits of maple and oak

Limited plasticity in functional root traits of maple and oak

Traits affecting the form and function of fine roots in woody plants show complex phenotypic variation. Lee et al. manipulate root segments of 2-year-old Acer rubrum and Quercus rubra seedlings in order to compare functional traits and trait plasticities in fine root tissues with natural and reduced levels of colonization by microbial symbionts. They find negligible plasticity for root diameter, branching intensity and nitrogen concentration across both species between levels of colonization. Roots with reduced colonization have decreased tissue density and increased specific root length, but species differences are significant and greater than treatment effects in traits other than tissue density. If common, such a result would greatly simplify and strengthen ecosystem- and community-level investigations that require information about the costs and benefits of constructing and maintaining fine root tissues.

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Understanding and forecasting the response of plants to climate change

Climate change effects on range and diversity of a fern

Climate change effects on range and diversity of a fern

Understanding and forecasting the response of plant species to climatic fluctuation is one of the top priorities for current biodiversity research because of the critical need to conserve and manage natural resources and biodiversity. Climate fluctuations are not a new phenomenon. Plants have responded to global, regional and local climate change via migration and/or adaptation since their origin. In turn, slow and/or little response to climate change (e.g. slow migration rate) increases the probability of local or global extinction. By constructing the spatio-temporal dynamics of plant response to climate change from the past, it may be possible to improve our ability to predict future changes in the range and distribution of species and their genetic diversity. Low diversity coincides with high climate change velocity.

Recently researchers have tried to untangle the response of plants to changing climates at the microevolutionary scale, by integrating species distribution models and statistical phylogeography. Combining these two techniques will not only overcome their individual limitations, but will also improve our understanding of the spatio-temporal population dynamics involved.

A recent paper in Annals of Botany uses species distribution modelling and population genetic analysis to assess how Asplenium fontanum, a fern species with high migration capacity, has responded to environmental change since the last ice-age and to predict possible future implications under global warming. The results show the importance of climatically stable areas for maintenance of populations and accumulation of genetic diversity, and indicate that such areas are vulnerable to extinction under future scenarios of climate change, resulting in possible permanent loss of historic genetic variation.

 

Bystriakova, N., Ansell, S.W., Russell, S.J., Grundmann, M., Vogel, J.C., & Schneider, H. Present, past and future of the European rock fern Asplenium fontanum: combining distribution modelling and population genetics to study the effect of climate change on geographic range and genetic diversity. (2014) Annals of Botany, 113(3), 453-465.
Climate change is expected to alter the geographic range of many plant species dramatically. Predicting this response will be critical to managing the conservation of plant resources and the effects of invasive species. The aim of this study was to predict the response of temperate homosporous ferns to climate change. Genetic diversity and changes in distribution range were inferred for the diploid rock fern Asplenium fontanum along a South–North transect, extending from its putative last glacial maximum (LGM) refugia in southern France towards southern Germany and eastern-central France. This study reconciles observations from distribution models and phylogeographic analyses derived from plastid and nuclear diversity. Genetic diversity distribution and niche modelling propose that genetic diversity accumulates in the LGM climate refugium in southern France with the formation of a diversity gradient reflecting a slow, post-LGM range expansion towards the current distribution range. Evidence supports the fern’s preference for outcrossing, contradicting the expectation that homosporous ferns would populate new sites by single-spore colonization. Prediction of climate and distribution range change suggests that a dramatic loss of range and genetic diversity in this fern is possible. The observed migration is best described by the phalanx expansion model. The results suggest that homosporous ferns reproducing preferentially by outcrossing accumulate genetic diversity primarily in LGM climate refugia and may be threatened if these areas disappear due to global climate change.

 

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Different responses of ephemerals and annuals to nitrogen

Different responses of ephemerals and annuals to nitrogen

Different responses of ephemerals and annuals to nitrogen

Biomass allocation patterns are important to ecosystem carbon cycles, and differ among species and in response to nutrient availability. Zhou et al. examine responses of ephemeral and annual plant species to different levels of nitrogen application in a desert environment, and find that compared to annuals, ephemerals grow more rapidly, increase shoot and root biomass with increasing nitrogen application rates and significantly decrease root/shoot quotients. However, an isometric log shoot vs. log root scaling relationship is maintained across all species. The results contribute to understanding how native species respond to N pollution and highlight that different life history strategies respond differently to nitrogen application.

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Seed dormancy and parasitic plants – this week in Annals of Botany

Acacia saligna Humidity-regulated dormancy onset in the Fabaceae: a conceptual model and its ecological implications for the Australian wattle Acacia saligna
Seed dormancy enhances fitness by preventing seeds from germinating when the probability of seedling survival and recruitment is low. The onset of physical dormancy is sensitive to humidity during ripening; however, the implications of this mechanism for seed bank dynamics have not been quantified. This study proposes a model that describes how humidity-regulated dormancy onset may control the accumulation of a dormant seed bank, and seed experiments are conducted to calibrate the model for an Australian Fabaceae, Acacia saligna. The model is used to investigate the impact of climate on seed dormancy and to forecast the ecological implications of human-induced climate change.

 

Arabinogalactan protein-rich cell walls, paramural deposits and ergastic globules define the hyaline bodies of rhinanthoid Orobanchaceae haustoria
Parasitic plants obtain nutrients from their hosts through organs called haustoria. The hyaline body is a specialized parenchymatous tissue occupying the central parts of haustoria in many Orobanchaceae species. The structure and functions of hyaline bodies are poorly understood despite their apparent necessity for the proper functioning of haustoria. This paper reports a cell wall-focused immunohistochemical study of the hyaline bodies of three species from the ecologically important clade of rhinanthoid Orobanchaceae.

 

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