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.

Special Issue on Plant Cell Walls – Free Online

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Although plants and many algae (e.g. the Phaeophyceae, brown, and Rhodophyceae, red) are only very distantly related they are united in their possession of carbohydrate-rich cell walls, which are of integral importance being involved in many physiological processes. Furthermore, wall components have applications within food, fuel, pharmaceuticals, fibres (e.g. for textiles and paper) and building materials and have long been an active topic of research. As the major deposit of photosynthetically fixed carbon, and therefore energy investment, cell walls are of undisputed importance to the organisms that possess them, the photosynthetic eukaryotes (plants and algae). The complexities of cell wall components along with their interactions with the biotic and abiotic environment are becoming increasingly revealed.

00 image for blog 2borderThe importance of plant and algal cell walls and their individual components to the function and survival of the organism, and for a number of industrial applications, are illustrated by the breadth of topics covered in a newly published Special Issue of Annals of Botany, containing 27 papers concentrating on various plants and algae, developmental stages, organs, cell wall components, and techniques. The papers are organized into topics under the general headings of (1) cell wall biosynthesis and remodelling, (2) cell wall diversity, and (3) application of new technologies to cell walls, and the Special Issue is available as FREE ACCESS online until 14 December.

00 image for blog 3borderIn their preface the Editors of this Special Issue, Zoë Popper, Marie-Christine Ralet and David Domozych, consider future directions within plant cell wall research. Expansion of the industrial uses of cell walls and potentially novel uses of cell wall components are both avenues likely to direct future research activities. Fundamentally, it is the continued progression from characterization (structure, metabolism, properties and localization) of individual cell wall components through to defining their roles in almost every aspect of plant and algal physiology that will present many of the major challenges in future cell wall research.

Accumulation of ferruginol in heartwood-forming xylem

Accumulation of ferruginol in heartwood-forming xylem

Accumulation of ferruginol in heartwood-forming xylem

Heartwood formation is a unique phenomenon of tree species but the mechanisms by which the substances involved accumulate are unclear. Kuroda et al. use time-of-flight secondary ion mass spectrometry (TOF-SIMS) in conjunction with quantitative analyses to study the distribution of ferruginol in a 30-year tree of Cryptomeria japonica (Taxodiaceae). They find that accumulation begins in the middle of the intermediate wood, initially in the earlywood near the annual ring boundary, then throughout the entire earlywood, and finally across to the whole annual ring in the heartwood. They conclude that the heterogeneous timing of ferruginol accumulation could be related to the distribution of ray parenchyma cells and/or water in the heartwood-forming xylem.

Cambial reactivation and formation of earlywood vessels in oak

Cambial reactivation and formation of earlywood vessels in oak

Cambial reactivation and formation of earlywood vessels in oak

The continuous formation of earlywood vessels is crucial for the growth of ring-porous hardwoods. Kudo et al. study Quercus serrate seedlings and find that a combination of localized heating and disbudding of dormant stems results in earlier cambial reactivation and differentiation of first vessel elements than in non-heated seedlings. A few narrow vessel elements are formed during heating after disbudding, while many large earlywood vessel elements are formed in heated seedlings with buds. The results suggest that elevated temperature is a direct trigger for differentiation of first vessel elements, and that whilst bud growth is not essential for differentiation of first vessel elements, it might be important for the continuous formation of wide vessel elements.

Heterozygosity–fitness correlations in pedunculate oak

Heterozygosity–fitness correlations in pedunculate oak

Heterozygosity–fitness correlations in pedunculate oak

Increased homozygosity caused by population fragmentation can directly affect individual plant fitness through the expression of deleterious alleles, and drought stress induced by climate change may exacerbate these effects. Vranckx et al. investigate various transpiration and growth traits of seedlings of pedunculate oak, Quercus robur, correlate them with their multilocus heterozygosity (MLH), and then study the effects of drought stress on these relationships. They find significant heterozygosity–fitness correlations for most fitness traits, and high atmospheric stress increases the strength of these correlations for the transpiration variables. They conclude that that ongoing climate change may strengthen the negative fitness responses to low MLH, highlighting the need to maximize individual multilocus heterozygosity in forest tree breeding programs.

Lathyrus diversity and crop improvement (Invited Review)

<i>Lathyrus</i> diversity and crop improvement (Invited Review)

Lathyrus diversity and crop improvement (Invited Review)

The Lathyrus genus (Fabaceae) includes 160 species, some of which have economic importance as food, fodder and ornamental crops (mainly L. sativus, L. cicera and L. odoratus, respectively) and are cultivated in over 1.5 million ha worldwide. Vaz Patto and Rubiales review the current status and future prospects of Lathyrus diversity conservation and characterization, highlighting their use in L. sativus and L. cicera breeding. They conclude that efforts for improvement of these species should concentrate on the development of publicly available joint core collections, and on high-resolution genotyping. This should result in more efficient and faster breeding approaches, which are especially needed for these neglected, under-utilized Lathyrus species.