Effects of pollination limitation and seed predation on female reproductive success of a deceptive orchid

13101S1R1For 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.

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Cause for optimism (maybe not…)

Image: Wikimedia Commons.

Image: Wikimedia Commons.

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.]

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Negative effects of global change on seed viability of juniper

Negative effects of global change on seed viability of juniper

Negative effects of global change on seed viability of juniper

Knowledge about the interacting effects of various global-change drivers on sexual reproduction of plants, one of their key mechanisms to cope with change, is limited. Gruwez et al. study common juniper (Juniperus communis), a poorly regenerating and hence threatened species, to determine the impact of various factors associated with global change on key stages in reproduction. They find that negative effects of increasing temperature and atmospheric depositions on seeds mostly became visible after embryo development, when seeds are ripe and ready for dispersal. However, damaging influences begin during the development of the gamethophytes and around the fertilization period. They suggest that the failure of natural regeneration in many European juniper populations may be attributable to climate warming as well as high atmospheric deposition of nitrogen and sulphur.

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Continuous, high-resolution biospeckle imaging of roots

Continuous, high-resolution biospeckle imaging of roots

Continuous, high-resolution biospeckle imaging of roots

Shining a laser onto biological material produces light speckles, and patterns of such biospeckle activity reflect changes in cell biochemistry, developmental processes and responses to the environment. Ribeiro et al. use a portable laser and a digital microscope to observe in situ biospeckle activity in roots of Zea mays, Jatropha curcas and Citrus limonia, and find that when a root encounters an obstacle the intensity of biospeckle activity decreases abruptly throughout the root system. The response becomes attenuated with repeated thigmostimuli. The data suggest that at least one component of root biospeckle activity results from a biological process, which is located in the zone of cell division and responds to thigmostimuli. The methodology presented is relatively inexpensive and portable, the analysis can be automated and the technique provides a rapid and sensitive functional assay.

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Developmental changes in root hydraulics (Research in Context)

Developmental changes in root hydraulics (Research in Context)

Developmental changes in root hydraulics (Research in Context)

Annual plants must increase root water uptake during development to match an increasing transpirational water loss by the shoot. Suku et al. study barley (Hordeum vulgare) plants during the early stages of vegetative development (9–28 d old) to determine by what means root water uptake is increased. They analyse individual roots, entire root systems and intact plants using a range of experimental approaches and find that although root hydraulic conductivity (representing root water uptake properties and including aquaporin function) increases in younger plants, the main means by which water uptake is increased during development is via an increase in root surface area.

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Orchid pollen, clover and salinity and Arabidopsis REM – This Week in Annals of Botany

Dactylorhiza maculata Desiccation tolerance, longevity and seed-siring ability of entomophilous pollen from UK native orchid species
Pollinator-limited seed-set in some terrestrial orchids is compensated for by the presence of long-lived flowers. This study tests the hypothesis that pollen from these insect-pollinated orchids should be desiccation tolerant and relatively long lived using four closely related UK terrestrial species; Anacamptis morio, Dactylorhiza fuchsii, D. maculata and Orchis mascula.

 

Heritability and quantitative genetic divergence of serotiny, a fire-persistence plant trait
Although it is well known that fire acts as a selective pressure shaping plant phenotypes, there are no quantitative estimates of the heritability of any trait related to plant persistence under recurrent fires, such as serotiny. In this study, the heritability of serotiny in Pinus halepensis is calculated, and an evaluation is made as to whether fire has left a selection signature on the level of serotiny among populations by comparing the genetic divergence of serotiny with the expected divergence of neutral molecular markers.

 

Leaf hydraulic vulnerability to drought is linked to site water availability across a broad range of species and climates
Vulnerability of the leaf hydraulic pathway to water-stress-induced dysfunction is a key component of drought tolerance in plants and may be important in defining species’ climatic range. However, the generality of the association between leaf hydraulic vulnerability and climate across species and sites remains to be tested.

 

Salinity-mediated cyanogenesis in white clover (Trifolium repens) affects trophic interactions
Increasing soil salinity poses a major plant stress in agro-ecosystems worldwide. Surprisingly little is known about the quantitative effect of elevated salinity on secondary metabolism in many agricultural crops. Such salt-mediated changes in defence-associated compounds may significantly alter the quality of food and forage plants as well as their resistance against pests. In this study, the effects of soil salinity on cyanogenesis in white clover (Trifolium repens), a forage crop of international importance, are analysed.

 

Analysis of the arabidopsis REM gene family predicts functions during flower development
The REM (Reproductive Meristem) gene family of Arabidopsis thaliana is part of the B3 DNA-binding domain superfamily. Despite the fact that several groups have worked on the REM genes for many years, little is known about the function of this transcription factor family. This study aims to identify a set of REM genes involved in flower development and to characterize their function.

 

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Prosopis: A global assessment of the biogeography, benefits, impacts and management of one of the world’s worst woody invasive plant taxa

14023S1R1Invasive species cause ecological, economic and social impacts and are key drivers of global change. This is the case for the genus Prosopis (mesquite; Fabaceae) where several taxa are among the world’s most damaging invasive species. Prosopis taxa are currently naturalised or invasive in 103 countries and are bioclimatically suitable for many more. There are numerous management practices available to control Prosopis invasions, each with their benefits and costs, however, in most areas management has had only limited success. In a new article published in AoB PLANTS, Shackleton et al. present a global review of Prosopis, focusing on its distribution, impacts, benefits and approaches to management. Key gaps in knowledge and promising options for management are highlighted.

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Variation of genes responsible for maturity loci in soybean

Variation of genes responsible for maturity loci in soybean

Variation of genes responsible for maturity loci in soybean

Soybean (Glycine max) is a typical short-day plant and several loci controlling flowering have been characterized. Whilst genes have been identified for loci E1 to E4, their degree of natural variation is unknown. Tsubokura et al. determine the sequences of these genes and their flanking regions for 39 accessions by primer walking, and perform systematic discrimination among alleles using DNA markers. Allelic combinations at the E1 to E4 loci are found to be associated with ecological types and about 62–66 % of variation of flowering time can be attributed to the loci. The results therefore suggest the existence of unidentified genes for flowering in soybean.

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One of a kind…

Image: Scott Zona/Wikimedia Commons.

Image: Scott Zona/Wikimedia Commons.

These articles have been going long enough(!) to be able now to report a successful outcome to a research project whose initiation was announced in a former news item entitled ‘Old meets new’. The project is the elucidation of the genome of Amborella trichopoda. “Amborella is a monotypic genus of rare understory [sic! What ever happened to understorEy??? - Ed.] shrubs or small trees endemic to… New Caledonia”.

Not only is this plant rare and monotypic – truly ‘one of a kind’! – but it is also probably the living – extant – flowering plant [angiosperm] that is closest evolutionarily to the earliest true first member of the angiosperm plant group, and may therefore be “the last survivor of a lineage that branched off during the dynasty’s earliest days, before the rest of the 350,000 or so angiosperm species diversified”. Given Amborella’s exalted status (which “represents the equivalent of the duck-billed platypus in mammals”), it is hoped that understanding its genetics will shed light on the evolution of the angiosperms as a whole. Indeed, the University of Bonn’s Dietmar Quandt is reported as describing Amborella as a more worthy model organism than Arabidopsis(!!!).

Since the angiosperms are probably the most ‘successful’ of all the groups in the Plant Kingdom (‘the land plants’, the Plantae), hopes are understandably high that unravelling the genome of Amborella – reported by the aptly named Amborella Genome Project – will lead to the identification of “the molecular basis of biological innovations that contributed to their geologically near-instantaneous rise to ecological dominance”. And accompanying the main nuclear genome article, Danny Rice et al. report on Amborella’s mitochondrial genome (mitochondria have some of their own DNA additional to that located in the nucleus) and find that numerous genes were acquired by horizontal gene transfer from other plants, including almost four entire mitochondrial genomes from mosses and algae. So, as ancient as it is, Amborella was still prepared to ‘learn’ from the experiences of even older land plants – mosses – and plant-like algae (which are in a different kingdom entirely to the land plants, the Protista). Adopt and adapt: a life lesson for all living things, I suggest.

[For more on this fascinating story, visit the home of the Amborella genome database. And if you still need some ‘proper’ botany (after all this genomery), you need look no further than Paula Rudall and Emma Knowles’ paper examining ultrastructure of stomatal development in early-divergent angiosperms (including Amborella…).  Notwithstanding all of this understandable present-day excitement, I can’t help but think that the importance of Amborella was foretold many decades ago, as "popular-in-the-mid-1970s" British-based pop band Fox seemingly declared: "things can get much better, under your Amborella…". Indeed! So, arabidopsis had better watch out! – Ed.]

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Reproduction and invasiveness in St. John’s wort

Reproduction and invasiveness in St. John’s wort

Reproduction and invasiveness in St. John’s wort

The relative ability of different plant taxa to invade new biogeographic regions successfully is dependent upon a number of biological and physical factors, one of which is the reproductive system, which directly influences population structure, gene flow and evolutionary potential. Considering seed formation, plants can reproduce through sex (selfing and outcrossing) or apomixis (asexual reproduction through seed.

St. John’s wort (Hypericum perforatum) is such an invasive species which is indigenous to central and eastern Europe; it is self-compatible and can reproduce through sex or apomixis. H. perforatum has successfully invaded North America since the first record of introduction in Lancaster, Pennsylvania in 1793. Its high genotypic plasticity in conjunction with variable levels of facultative apomixis are hypothesized to have contributed to its rapid spread throughout the continent. For example, in an analysis of multiple phenotypic traits, Maron et al. (2004) demonstrated that the introduction of H. perforatum into North America was accompanied by rapid climatic adaptation.

Using an analysis of a collection of European native and North American invasive accessions, a recent paper in Molins Annals of Botany examines biogeographic differentiation in both natural and introduced populations, and test whether variation in apomixis traits is correlated with the propensity for H. perforatum to invade novel environments.

 

Molins, M.P., Corral, J.M., Aliyu, O.M., Koch, M.A., Betzin, A., Maron, J.L., & Sharbel, T.F. (2014) Biogeographic variation in genetic variability, apomixis expression and ploidy of St. John’s wort (Hypericum perforatum) across its native and introduced range. Annals of Botany, 113 (3): 417-427 doi: 10.1093/aob/mct268.
St. John’s wort (Hypericum perforatum) is becoming an important model plant system for investigations into ecology, reproductive biology and pharmacology. This study investigates biogeographic variation for population genetic structure and reproduction in its ancestral (European) and introduced (North America) ranges. Over 2000 individuals from 43 localities were analysed for ploidy, microsatellite variation (19 loci) and reproduction (flow cytometric seed screen). Most individuals were tetraploid (93 %), while lower frequencies of hexaploid (6 %), diploid (<1 %) and triploid (<1 %) individuals were also identified. The presence of pure and mixed populations representing all three genetic clusters in North America demonstrates that H. perforatum was introduced multiple times onto the continent, followed by gene flow between the different gene pools. Taken together, the data presented here suggest that plasticity in reproduction has no influence on the invasive potential of H. perforatum.

 

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