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.
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.]
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.
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.
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.
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.
Four decades of intensive research into anthropogenically induced shifts in CO2, precipitation, and temperature evidence important biological impacts on many plant species. As ecologists develop more sophisticated experiments however, many unexpected responses become apparent, suggesting that response to climate change in real world vegetation is more complex than the experiments and models of past decades could be expected to anticipate. Nonetheless, these complexities must be understood if we are to have any hope of predicting the effects of anthropogenic climate change on biological systems.
In this Symposium session at ESA 2014, we focus on surprises in plant responses, highlighting mismatches between theory, modelling, experimental and observational studies. We bring together expertise from multiple levels of study (from individual to ecosystems), using manifold approaches (from experimental to modelling to observational), and from ecological, evolutionary and paleo perspectives. Speakers span a range of career stages, from well-established to just finishing their PhDs and include perspectives from four continents (North America, Africa, Asia and Australia).
By bringing together this diversity of topics, approaches and perspectives, we aim to gain new insights and promote future interdisciplinary research on plant/climate interactions.
We hope you’ll be able to join us in Sacramento.
Camille Parmesan, Marine Institute, University of Plymouth, UK. and
Mick Hanley, School of Biological Sciences, University of Plymouth, UK.
13:30 – Richard Primack (University of Boston, USA) Autumn leaf phenology: A search for patterns using 1000 species at four botanical gardens
14:00 – Susan P. Harrison (University of California – Davis, USA) Ecological contingency in the effects of climate change on plant communities: reconciling experimental, historical, interannual, and geographic evidence
14:30 – Kumar P. Mainali (University of Texas at Austin, USA) Complex drivers of population dynamics across treeline: expected and unexpected responses in Himalayan systems
15:10 – Osvaldo Sala (Arizona State University, USA) Lags in the response of ecosystems to directional changes in water availability
15:40 – Tianhua He (Curtin University, Perth, Australia) In situ evolutionary adaptation of Australian plants to climate change
16:10 – Guy Midgley (Stellenbosch University, South Africa) Individualistic species vs. ecosystem responses in under changing climate and CO2 conditions
16:40 Panel Discussion
Annals of Botany Special Issue
The Annals of Botany journal expects to publish work presented at Sacramento as part of a special issue on Plants and Climate Change in the early part of 2015.
The journal welcomes submission of relevant papers from any plant biologist or ecologist for publication in this special issue. Please contact Mick Hanley (mehanley(at)plymouth.ac.uk) for more details.
In some species, epicotyl dormancy break in seeds that have deep simple epicotyl morphophysiological dormancy requires a certain root length to be attained, but the mechanisms associated with this are unclear. Hao et al.study seeds of Tibetan peony (Paeonia ludlowii) and find that a root length of ≥6 cm is necessary before dormancy can be released by cold stratification. They determine that root length increases the ratio of GA3/ABA of the epicotyl in the seeds, with ABA accumulation decreasing with increasing root length. They conclude that the epicotyl becomes sensitive to cold stratification once a certain ratio is reached.
For many species of conservation significance, multiple factors limit reproduction. In a new study published in AoB PLANTS, Walsh et al. examined the contribution of plant height, number of flowers, number of stems, as well as the joint impacts of mutualists and antagonists on the pollination biology and seed production of the imperiled, deceptive orchid, Cypripedium candidum. They found flowering stem height to be the only morphological feature significant in reproduction, with taller flowering stems simultaneously receiving increased pollination and decreased seed predation. Furthermore they found decreased seed mass in individuals subjected to hand-self pollination treatments. Their results may help explain the factors limiting seed production in other Cypripedium and further emphasize the importance of management in orchid conservation.
As an ‘old-fashioned’ botanist my heart was gladdened to see that Number 1 in the ‘Top 10 most viewed Plant Science research articles in 2013’ from Frontiers in Plant Science was one that dealt with fundamental botany of the taxonomic kind. The paper in question was entitled ‘Angiosperm-like pollen and Afropollis from the Middle Triassic (Anisian) of the Germanic Basin (Northern Switzerland)’ and was written by Peter Hochuli and Susanne Feist-Burkhardt. Whilst that recognition may engender a feel-good view that plant taxonomy is doing rather well, Quentin Wheeler’s timely New Phytologist Commentary, ‘Are reports of the death of taxonomy an exaggeration?’, offers a more cautious interpretation. Commenting upon an article by Daniel Bebber et al., he concludes that plant taxonomy (though one suspects taxonomy of all biota fares as badly) is still in desperate need of greater attention – in terms of people to undertake the work and appropriate funding – as befits its importance to a true appreciation of the planet’s biodiversity and the inter-relationships between living things. Sadly, this state of affairs is unlikely to be helped by news that the Royal Botanic Gardens at Kew (London, UK) – one of the world’s premier centres of plant taxonomic endeavour – is in the midst of a funding crisis. Indeed, the situation is apparently so bad that ‘about 125 jobs could be cut as… Kew… faces a £5m shortfall in revenue in the coming financial year’. This must be particularly concerning since it comes shortly after news that visitor numbers to Kew increased by 29% last year compared to 2012. And this bad news on the plant taxonomy front is echoed in the USA where ‘too few scientists are being trained in agriculture areas of science’. So, there’s an insufficiency of people to grow the new crops that aren’t being identified because of the dearth of plant taxonomists. Where will it all end..?
[If you’re not put off by the precarious state of life as a taxonomist and want a little bit more of a career insight, then you could do much worse that read Elisabeth Pain’s ‘Science Careers’ article. And for a welcome boost to publicising the plight of the endangered species known as Taxonomus non-vulgaris var. biologicus, see Tim Entwisle’s news article in The Guardian – Ed.]