Belowground legacies of Pinus contorta invasion and removal result in multiple mechanisms of invasional meltdown

14095R1 Ian Dickie thumbnailInvasive plants alter plant communities and transform landscapes aboveground, but also have strong belowground effects that are potentially even more important to ecosystem outcomes. In a new study published in AoB PLANTS using management treatments of the widespread invasive tree, Lodgepole Pine, Dickie et al. found that pines and pine removal transform belowground ecosystems, increasing ectomycorrhizal inoculum and driving a change from slow-cycling fungal-dominated soils to fast-cycling bacterial-dominated soils with increased nutrient availability. This results in increased growth of graminoids, particularly exotic grasses, and facilitation of Douglas-fir establishment, hindering ecosystem restoration. The results highlight the importance of considering multiple species interactions in invasion, particularly in terms of belowground legacies.

 

Molecular analysis and evolution of forisomes

Molecular analysis and evolution of forisomes

Molecular analysis and evolution of forisomes

Forisomes are specialized structural phloem proteins that mediate sieve element occlusion after wounding exclusively in papilionoid legumes, but most studies of their structure and function have focused on the Old World clade rather than the early lineages. Müller et al. combine sequence analysis and bioinformatics with structural and functional analysis of native forisomes and artificial forisome-like protein bodies, the latter produced by expressing forisome genes from different legumes in a heterologous background. They conclude that forisome structure and function have been strongly conserved during evolution and that species-dependent subsets of SEO-F proteins may have evolved to fine-tune the structure of native forisomes.

Sponsor a genome…?

Image: Kurt Stüber/Wikimedia Commons.

Image: Kurt Stüber/Wikimedia Commons.

Crowdsourcing – ‘the practice of obtaining needed services, ideas, or content by soliciting contributions from a large group of people, and especially from an online community, rather than from traditional employees or suppliers’ –was the name of the game a few years ago. And in a biological context it was famously exploited to investigate protein folding using the program/‘game’ FoldIt. And so skillful have participants in this exercise become that their combined talents are now being exploited to design completely new proteins, such as new catalysts for photosynthesis.

Helping plant science we also now have crowdfunding, ‘the collection of finance from backers — the “crowd” — to fund an initiative and which usually occurs on Internet platforms’. And an intriguing example of this phenomenon is the call for funds to help sequence the genome of Azolla filiculoides by a team based at Professor Kathleen Pryer’s Seed-Free Vascular Plants laboratory at Duke University (Durham, North Carolina, USA), in collaboration with Professor Paul Wolf at Utah State University (USA). The funding opportunity is hosted by the appropriately named ‘Experiment’, a ‘platform for enabling new scientific discoveries’. Although you might expect universities to be funding the research, that has become increasingly difficult to secure and might not always be forthcoming, especially in cases of ‘risky’ projects. That’s where organisations such as Experiment, which exists to help secure funding that will allow new ideas to get off the ground, especially ‘the innovative and high-risk ideas with the biggest impact’, come into their own. Acting primarily as a shop window, Experiment advertise projects to would-be sponsors – who in true egalitarian style can be anybody, true citizen science in action – and only charge a fee for their services when the project becomes fully funded. And at 8% of the funding total secured that fee is much lower than normal university overhead charges, which take large shares of research funding provided by more traditional sources such as government-funded research organisations!

Anyway, back to the Azolla project. The modest sum of US$15 000 is sought to generate a draft sequence of the genomes of Azolla and its symbiotic N-fixing bacteria, with a view to understanding the two-way, inter-kingdom language that codes for the molecular machinery underlying this symbiotic partnership, and possibly tailor it to suit our needs. Why? Azolla is a ‘superorganism’, consisting of not just the fern but also a diverse array of symbiotic bacteria. It is this unique microbiota that converts nitrogen into organic forms and makes Azolla a perfect bio-fertilizer. In a world where we are ever more concerned about pollution by increasing use of synthetic fertilisers to increase crop yields to meet an increasing demand for food by a growing human population, you might think that this is the sort of project that should be funded by tax dollars extracted from the populace by governments, rather than expecting their already-taxed citizenry to dig into their own pockets effectively twice over. But it always pays to look at the fine print: ‘Genomic sequencing of this unique Azolla–Nostoc system would cost well under $1 million’. Whilst $15k is well under $1 million, I suspect the final figure required will be much closer to $1 million than $15k, which I guess is what’s hinted at behind the text ‘as a start, the funding of $15 000 will get us reasonably good quality genomes [P. Cuttings’ emphasis] for the Azolla superorganism that can jumpstart various exciting research programs’ in the project’s ‘budget overview’. Maybe more traditional sources of funding will pick up the remaining US$985 000 if the project’s potential is demonstrated on the shoestring budget? If only because, although approximately US$1 million is considerably more than the $15 000 sought, that’s ‘far less than the $8 billion each year that US farmers pay for nitrogen fertilizer’ – much of which finds its way into rivers and streams, damaging delicate water systems. This small step toward potentially helping crops to use less synthetic nitrogen could benefit farmers’ bottom lines, the environment and the prices we pay for food’. Hear, hear! And as I write this on 9th June 2014 there are 32 days left to pledge and add to the then-current total of US$1625. Good luck securing the rest of the funding!

 

[What we haven’t got space to go into here – but which also emphasises another unique characteristic of Azolla – is the role it played in global cooling in the Arctic Azolla Event of 50 million years ago. A famously fascinating fern, indeed! – Ed.]

Hydrometeorology and ecophysiology of cloud forests

Hydrometeorology and ecophysiology of cloud forests

Hydrometeorology and ecophysiology of cloud forests

Tropical montane cloud forests (TMCFs) are characterized by a unique set of biological and hydroclimatic features, including frequent and/or persistent fog, cool temperatures, and high biodiversity and endemism. These forests are one of the most vulnerable ecosystems to climate change given their small geographic range, high endemism and dependence on a rare microclimatic envelope. The frequency of atmospheric water deficits for some cloud forests is likely to increase in the future, but the consequences for the integrity and distribution of these ecosystems are uncertain. In order to investigate plant and ecosystem responses to climate change, we need to know how cloud forest species function in response to current climate, which factors shape function and ecology most and how these will change into the future.

A recent review in Annals of Botany focuses on recent ecophysiological research of cloud forest plants to establish a link between hydrometeorological conditions and vegetation distribution, functioning and survival. The hydraulic characteristics of cloud forest trees are discussed, together with the prevalence and ecological consequences of foliar uptake of fog water, a key process that allows efficient acquisition of water during cloud immersion periods, minimizing water deficits and favouring survival of species prone to drought-induced hydraulic failure.

Fog occurrence is the single most important microclimatic feature affecting the distribution and function of cloud forest plants. Plants in cloud forests are very vulnerable to drought (possessing a small hydraulic safety margin), and the presence of fog and water uptake minimizes the occurrence of tree water deficits and thus favours the survival of cloud forest trees where such deficits may occur. Characterizing the interplay between microclimatic dynamics and plant water relations is key to foster more realistic projections about climate change effects on cloud forest function and distribution.

Oliveira, R.S., Eller, C. B., Bittencourt, P.R., and Mulligan, M. (2014). The hydroclimatic and ecophysiological basis of cloud forest distributions under current and projected climates. Annals of Botany, 113(6): 909-920. doi: 10.1093/aob/mcu060

Variation of flowering and pseudovivipary in Poa

Variation of flowering and pseudovivipary in <i>Poa</i>

Variation of flowering and pseudovivipary in Poa

Pseudovivipary is an intriguing asexual reproduction trait in which plantlets and bulbils develop instead of normal florets. Ofir and Kigel study inter-annual and intra-clonal stability of flowering and pseudovivipary across a rainfall gradient in clones of the summer-dormant grass Poa bulbosa and find large variability in reproductive behaviour, without a distinct time sequence of flowering and pseudovivipary across years. Pseudivivipary is enhanced by photoperiods less inductive of flowering, and inter-annual variation in flowering and psudovivipary is attributed to differences in the onset of the rainy season that result in different day-length and temperature conditions during the early stages of growth, which is when induction of flowering and dormancy occurs.

Pollinator discrimination, acorn antiques and fossil climates – new this week in Annals of Botany

Geranium maculatum Frequency-dependent pollinator discrimination acts against female plants in the gynodioecious Geranium maculatum
Gynodioecy, the co-occurrence of female and hermaphroditic individuals, is thought to be an intermediate step between hermaphroditism and separate sexes, a major transition in flowering plants. This paper suggests that suggest that pollinator discrimination negatively affects females’ relative fitness when they are rare. Thus the initial spread of females in a population, the first step in the evolution of gynodioecy, may be made more difficult due to pollinator discrimination.

Factors affecting stress tolerance in recalcitrant embryonic axes from seeds of four Quercus (Fagaceae) species native to the USA or China
Oaks (Quercus species) are often considered ‘foundation’ components of temperate and/or subtropical forest ecosystems. However, the populations of some species are declining and there is considerable urgency to develop ex situ conservation strategies. In this study, the storage physiology of seeds within Quercus was explored in order to determine factors that affect survival during cryopreservation and to provide a quantitative assessment of seed recalcitrance to support future studies of this complex trait.

Multiple origins of circumboreal taxa in Pyrola (Ericaceae), a group with a Tertiary relict distribution
Two major categories of Northern Hemisphere intercontinental disjunctions are Tertiary relict disjunctions and circumboreal distributions. Tertiary relict disjunctions tend to be older and involve groups from warm temperate to sub-tropical regions, reflecting the warm climates of the Tertiary epoch. Conversely, circumboreal distributions typically involve cold temperate to Arctic-Alpine species, and tend to be younger, reflecting the recent development of these biomes due to global cooling over the past 5 million years. This paper reconstructs the biogeographic history of Pyrola based on a clear phylogenetic analysis and to explore how the genus attained its circumboreal distribution.

Strigolactones, brassinosteroids and autoregulation of nodulation

Strigolactones, brassinosteroids and autoregulation of nodulation

Strigolactones, brassinosteroids and autoregulation of nodulation

The symbiosis between legumes and N-fixing rhizobia bacteria is energy intensive, and as a result plants regulate nodulation via hormones and mechanisms such as the autoregulation of nodulation (AON) system. Foo et al. investigate interactions between the AON system and two hormones recently shown to promote nodulation, strigolactones and brassinosteroids. They find that double-mutant plants of pea (Pisum sativum) that are disrupted in elements of the AON pathway and that are also strigolactone- or brassinosteroid-deficient display supernodulating AON mutant phenotypes. Strigolactone production is not consistently affected in the AON mutants, and the results indicate that strigolactones and brassinosteroids do not act downstream of the AON genes examined. They argue that it is likely that these hormones act independently of the AON system to promote nodule formation.

Ureide accumulation and drought inhibition of N2fixation

Ureide accumulation and drought inhibition of N<sub>2</sub>fixation

Ureide accumulation and drought inhibition of N2fixation

Legume nitrogen fixation is inhibited by soil water deficit and under drought conditions ureidic legumes, such as common bean and soybean, accumulate ureides, which are the main products of N2 fixation in these plants. Coleto et al. study genotypes of common bean, Phaseolus vulgaris, with variable degrees of N2-fixation tolerance to water stress, and find variable accumulation of ureides in their leaves. There is no accumulation of ureides in the nodules of any of the genotypes and the rise in leaves occurs even after complete inhibition of N2-fixation, probably as the result of remobilization of nitrogen from stressed tissues. They therefore conclude that shoot ureide accumulation after prolonged exposure to drought is not a cause of feedback inhibition of nitrogen fixation.

Clear way ahead for leaf research

Image: Benjamin Blonder/Cleared Leaf Image Database.

Image: Benjamin Blonder/Cleared Leaf Image Database.

Databases (collections of information that are organised ‘so that it can easily be accessed, managed, and updated’) are everywhere these days and, as repositories of data that can be explored by interested parties – and maybe new connections made and insights revealed – they are an extremely useful resource for science. Indeed, access to large data sets is so important to modern-day scientific endeavour that a new journal has recently been established to publish the outcome of such studies. Scientific Data is an open-access, online-only publication for descriptions of scientifically valuable datasets that exists to help you publish, discover and reuse research data and will ‘complement and promote public data repositories’. And in the tradition of science belonging to us all, the journal’s primary article type, the ‘Data Descriptor’, is designed to make your data more discoverable, interpretable and reusable. However, for such journals to achieve their noble and philanthropic aims, the necessary databases of ‘stuff’ need to exist – or be created. One such facility whose birth caught my eye(!) recently was the ClearedLeavesDB, an online database of cleared plant leaf images – its existence and purpose has been highlighted by Abhiram Das et al., who developed it. Leaf vein networks (LVNs) are important to both the structure and function of leaves and there is a growing body of work linking LVN structure to the physiologyecology and evolution of land plants. Recognising the importance of LVNs, the team developed this digital archive that enables online viewing, sharing and disseminating of collections of images of cleared leaves (which usually have the LVNs enhanced) held by both institutions and individual researchers. We applaud this initiative and trust that its objectives – to facilitate research advances in the study of leaf structure and function, to preserve and archive cleared leaf data in an electronic, accessible format, and to promote the exchange of new data and ideas for the plant biology community – are met.