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Ann Bot is a gestalt entity who works in the office for the Annals of Botany.

Limonium, bursts of CO2 release and Na+/K+ homeostasis at the whole-plant level – What’s New in Annals of Botany this week

Type specimen of Limonium maritimum Taxonomic complexity in the halophyte Limonium vulgare and related taxa (Plumbaginaceae): insights from analysis of morphological, reproductive and karyological data
Limonium is a well-known example of a group of plants that is taxonomically complex due to certain biological characteristics that hamper species’ delineation. The closely related polyploid species Limonium vulgare Mill., L. humile Mill. and L. narbonense Mill. are defined species and can be used for studying patterns of morphological and reproductive variation. The first two taxa are usually found in Atlantic Europe and the third in the Mediterranean region, but a number of intermediate morphological forms may be present alongside typical examples of these species. This study attempts to elucidate morphological, floral and karyological diversity representative of these taxa in the Iberian Peninsula.

 

Bursts of CO2 released during freezing offer a new perspective on avoidance of winter embolism in trees
Woody plants can suffer from winter embolism as gas bubbles are formed in the water-conducting conduits when freezing occurs: gases are not soluble in ice, and the bubbles may expand and fill the conduits with air during thawing. A major assumption usually made in studies of winter embolism formation is that all of the gas dissolved in the xylem sap is trapped within the conduits and forms bubbles during freezing. The current study tested whether this assumption is actually valid, or whether efflux of gases from the stem during freezing reduces the occurrence of embolism.

 

ZxNHX controls Na+ and K+ homeostasis at the whole-plant level in Zygophyllum xanthoxylum through feedback regulation of the expression of genes involved in their transport
In order to cope with arid environments, the xerohalophyte Zygophyllum xanthoxylum efficiently compartmentalizes Na+ into vacuoles, mediated by ZxNHX, and maintains stability of K+ in its leaves. However, the function of ZxNHX in controlling Na+ and K+ homeostasis at the whole-plant level remains unclear. In this study, the role of ZxNHX in regulating the expression of genes involved in Na+ and K+ transport and spatial distribution was investigated.

 

Bizarre flowers, chloride ions and auxin, and the role of pectin in stomatal development – this week in Annals of Botany

Emmotum harleyi Floral structure of Emmotum (Icacinaceae sensu stricto or Emmotaceae), a phylogenetically isolated genus of lamiids with a unique pseudotrimerous gynoecium, bitegmic ovules and monosporangiate thecae
The Icacinaceae consist of a group of early branching lineages of lamiids whose relationships are not yet resolved and whose detailed floral morphology is poorly known. The most bizarre flowers occur in Emmotum: the gynoecium has three locules on one side and none on the other. It has been interpreted as consisting of three fertile and two sterile carpels or of one fertile carpel with two longitudinal septa and two sterile carpels. This study focuses on the outer and inner morphology of the gynoecium to resolve its disputed structure.

 

Molecular cloning of two novel peroxidases and their response to salt stress and salicylic acid in the living fossil Ginkgo biloba
Peroxidase isoenzymes play diverse roles in plant physiology, such as lignification and defence against pathogens. The actions and regulation of many peroxidases are not known with much accuracy. A number of studies have reported direct involvement of peroxidase isoenzymes in the oxidation of monolignols, which constitutes the last step in the lignin biosynthesis pathway. However, most of the available data concern only peroxidases and lignins from angiosperms. This study describes the molecular cloning of two novel peroxidases from the ‘living fossil’ Ginkgo biloba and their regulation by salt stress and salicylic acid.

 

Role of chloride ions in the promotion of auxin-induced growth of maize coleoptile segments
The mechanism of auxin action on ion transport in growing cells has not been determined in detail. In particular, little is known about the role of chloride in the auxin-induced growth of coleoptile cells. Moreover, the data that do exist in the literature are controversial. This study describes experiments carried out with maize, a classical model system for studies of plant cell elongation growth. These results suggest that chloride ions play a role in the IAA-induced growth of maize coleoptile segments.

 

Developmental changes in guard cell wall structure and pectin composition in the moss Funaria: implications for function and evolution of stomata
In seed plants, the ability of guard cell walls to move is imparted by pectins. Arabinan rhamnogalacturonan I (RG1) pectins confer flexibility while unesterified homogalacturonan (HG) pectins impart rigidity. Recognized as the first extant plants with stomata, mosses are key to understanding guard cell function and evolution. Moss stomata open and close for only a short period during capsule expansion. This study examines the ultrastructure and pectin composition of guard cell walls during development in Funaria hygrometrica and relates these features to the limited movement of stomata. This is the first study to demonstrate changes in pectin composition during stomatal development in any plant.

 

Arabidopsis growth, shading and halophyte-based agriculture – new in Annals of Botany this week

Growth rate distribution in the forming lateral root of arabidopsis Growth rate distribution in the forming lateral root of arabidopsis
Microscopic observations of lateral roots (LRs) in Arabidopsis thaliana reveal that the cross-sectional shape of the organ changes from its basal to its apical region. The founder cells for LRs are elongated along the parent root axis, and thus from the site of initiation the base of LRs resemble an ellipse. The circumference of the apical part of LRs is usually a circle. The objective of this study was to analyse the characteristics of changes in the growth field of LRs possessing various shapes in their basal regions. This is the first report of a description of growth of an asymmetric plant organ using the growth tensor method. The mathematical modelling adopted in the study provides new insights into plant organ formation and shape.

 

Contribution of above- and below-ground plant traits to the structure and function of grassland soil microbial communities
Abiotic properties of soil are known to be major drivers of the microbial community within it. Our understanding of how soil microbial properties are related to the functional structure and diversity of plant communities, however, is limited and largely restricted to above-ground plant traits, with the role of below-ground traits being poorly understood. This study investigates the relative contributions of soil abiotic properties and plant traits, both above-ground and below-ground, to variations in microbial processes involved in grassland nitrogen turnover.

 

Responses to shading of naturalized and non-naturalized exotic woody species
Recent studies have suggested that responses to shading gradients may play an important role in establishment success of exotic plants, but hitherto few studies have tested this. Therefore, a common-garden experiment was conducted using multiple Asian woody plant species that were introduced to Europe >100 years ago in order to test whether naturalized and non-naturalized species differ in their responses to shading. Specifically, a test was carried out to determine whether naturalized exotic woody species maintained better growth under shaded conditions, and whether they expressed greater (morphological and physiological) adaptive plasticity in response to shading, relative to non-naturalized species.

 

The development of halophyte-based agriculture: past and present
Freshwater comprises about a mere 2·5 % of total global water, of which approximately two-thirds is locked into glaciers at the polar ice caps and on mountains. In conjunction with this, in many instances irrigation with freshwater causes an increase in soil salinity due to overirrigation of agricultural land, inefficient water use and poor drainage of unsuitable soils. The problem of salinity was recognized a long time ago and, due to the importance of irrigated agriculture, numerous efforts have been devoted towards improving crop species for better utilization of saline soils and water. Irrigating plants with saline water is a challenge for practitioners and researchers throughout the world. This review critically analyses past and present halophyte-based production systems in the context of genetics, physiology, agrotechnical issues and product value. There are still difficulties that need to be overcome, such as direct germination in saline conditions or genotype selection. However, more and more research is being directed not only towards determining salt tolerance of halophytes, but also to the improvement of agricultural traits for long-term progress.

 

Lichens and their symbionts, seed size and much more – This Week in Annals of Botany

Morphology and anatomy of Trebouxia species isolated in axenic culture Photobiont selectivity leads to ecological tolerance and evolutionary divergence in a polymorphic complex of lichenized fungi
The integrity and evolution of lichen symbioses depend on a fine-tuned combination of algal and fungal genotypes. Geographically widespread species complexes of lichenized fungi can occur in habitats with slightly varying ecological conditions, and it remains unclear how this variation correlates with symbiont selectivity patterns in lichens. In an attempt to address this question, more than 300 samples were taken of the globally distributed and ecologically variable lichen-forming species complex Tephromela atra, together with closely allied species, in order to study genetic diversity and the selectivity patterns of their photobionts.

 

The presence of a below-ground neighbour alters within-plant seed size distribution in Phaseolus vulgaris
Considerable variation in seed size commonly exists within plants, and is believed to be favoured under natural selection. This study aims to examine the extent to which seed size distribution depends on the presence of competing neighbour plants. Below-ground neighbour presence affects within-plant seed size distribution in P. vulgaris. This effect appears to be non-resource-mediated, i.e. to be independent of neighbour-induced effects on resource availability. It implies that, based on current environmental cues, plants can make an anticipatory adjustment of their investment strategy in offspring as an adaptation to the local environment in the future.

 

Extensive long-distance pollen dispersal and highly outcrossed mating in historically small and disjunct populations of Acacia woodmaniorum (Fabaceae), a rare banded iron formation endemic
Understanding patterns of pollen dispersal and variation in mating systems provides insights into the evolutionary potential of plant species and how historically rare species with small disjunct populations persist over long time frames. This study aims to quantify the role of pollen dispersal and the mating system in maintaining contemporary levels of connectivity and facilitating persistence of small populations of the historically rare Acacia woodmaniorum.

 

An angiosperm-wide analysis of the gynodioecy-dioecy pathway
About 6 % of an estimated total of 240 000 species of angiosperms are dioecious. The main precursors of this sexual system are thought to be monoecy and gynodioecy. A previous angiosperm-wide study revealed that many dioecious species have evolved through the monoecy pathway; some case studies and a large body of theoretical research also provide evidence in support of the gynodioecy pathway. If plants have evolved through the gynodioecy pathway, gynodioecious and dioecious species should co-occur in the same genera. However, to date, no large-scale analysis has been conducted to determine the prevalence of the gynodioecy pathway in angiosperms. In this study, this gap in knowledge was addressed by performing an angiosperm-wide survey in order to test for co-occurrence as evidence of the gynodioecy pathway.

 

Arrangement of mixed-linkage glucan and glucuronoarabinoxylan in the cell walls of growing maize roots
Plant cell enlargement is unambiguously coupled to changes in cell wall architecture, and as such various studies have examined the modification of the proportions and structures of glucuronoarabinoxylan and mixed-linkage glucan in the course of cell elongation in grasses. However, there is still no clear understanding of the mutual arrangement of these matrix polymers with cellulose microfibrils and of the modification of this architecture during cell growth. This study aimed to determine the correspondence between the fine structure of grass cell walls and the course of the elongation process in roots of maize.

 

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.

 

Plants and Climate Change: Complexities and Surprises

Photo: BigStockPhoto.

Photo: BigStockPhoto.

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.

Speakers

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.

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.

 

This Week in Annals of Botany

Light microscopy images of wood Automatic identification and characterization of radial files in light microscopy images of wood
Analysis of anatomical sections of wood provides important information for understanding the secondary growth and development of plants. This study reports on a new method for the automatic detection and characterization of cell files in wood images obtained by light microscopy.

 

Using virtual 3-D plant architecture to assess fungal pathogen splash dispersal in heterogeneous canopies: a case study with cultivar mixtures and a non-specialized disease causal agent
Recent developments in plant disease management have led to a growing interest in alternative strategies, such as increasing host diversity and decreasing the use of pesticides. Use of cultivar mixtures is one option, allowing the spread of plant epidemics to be slowed down. As dispersal of fungal foliar pathogens over short distances by rain-splash droplets is a major contibutor to the spread of disease, this study focused on modelling the physical mechanisms involved in dispersal of a non-specialized pathogen within heterogeneous canopies of cultivar mixtures, with the aim of optimizing host diversification at the intra-field level.

 

AGO1 controls arabidopsis inflorescence architecture possibly by regulating TFL1 expression
The TERMINAL FLOWER 1 (TFL1) gene is pivotal in the control of inflorescence architecture in arabidopsis. Thus, tfl1 mutants flower early and have a very short inflorescence phase, while TFL1-overexpressing plants have extended vegetative and inflorescence phases, producing many coflorescences. TFL1 is expressed in the shoot meristems, never in the flowers. In the inflorescence apex, TFL1 keeps the floral genes LEAFY (LFY) and APETALA1 (AP1) restricted to the flower, while LFY and AP1 restrict TFL1 to the inflorescence meristem. In spite of the central role of TFL1 in inflorescence architecture, regulation of its expression is poorly understood. This study aims to expand the understanding of inflorescence development by identifying and studying novel TFL1 regulators.

 

Explaining ontogenetic shifts in root-shoot scaling with transient dynamics
Simple models of herbaceous plant growth based on optimal partitioning theory predict, at steady state, an isometric relationship between shoot and root biomass during plant ontogeny, i.e. a constant root–shoot ratio. This prediction has received mixed empirical support, suggesting either that optimal partitioning is too coarse an assumption to model plant biomass allocation, or that additional processes need to be modelled to account for empirical findings within the optimal partitioning framework. In this study, simulations are used to compare quantitatively two potential explanations for observed non-isometric relationships, namely nutrient limitation during the experiments and initial developmental constraints.

 

Callose biosynthesis in arabidopsis with a focus on pathogen response: what we have learned within the last decade
(1,3)-β-Glucan callose is a cell wall polymer that is involved in several fundamental biological processes, ranging from plant development to the response to abiotic and biotic stresses. Despite its importance in maintaining plant integrity and plant defence, knowledge about the regulation of callose biosynthesis at its diverse sites of action within the plant is still limited. Arabidopsis (Arabidopsis thaliana) is one of the best-studied models not only for general plant defence responses but also for the regulation of pathogen-induced callose biosynthesis. This article summarizes what is known about the regulation of callose synthase activity as well as what has been discussed with regard to this topic within the last decade based on results derived from new techniques and available mutant lines, focusing on the progress that has been made in understanding the regulation of callose biosynthesis in response to pathogen attack.

 

Linking ecophysiological modelling with quantitative genetics to support marker-assisted crop design for improved yields of rice under drought stress
Genetic markers can be used in combination with ecophysiological crop models to predict the performance of genotypes. Crop models can estimate the contribution of individual markers to crop performance in given environments. This study explores the use of crop models to design markers and virtual ideotypes for improving yields of rice (Oryza sativa) under drought stress.

 

Impact of climate on plant growth and flower formation – This Week in Annals of Botany

Xylem Impact of warming and drought on carbon balance related to wood formation in black spruce
Wood formation in trees represents a carbon sink that can be modified in the case of stress. The way carbon metabolism constrains growth during stress periods (high temperature and water deficit) is now under debate. In this study, the amounts of non-structural carbohydrates for xylogenesis in black spruce saplings were assessed under high temperature and drought in order to determine the role of sugar mobilization for osmotic purposes and its consequences for secondary growth. Plant water status during wood formation can influence the materials available for growth in the cambium and xylem.

 

Relative growth rate variation of evergreen and deciduous savanna tree species is driven by different traits
Plant relative growth rate depends on biomass allocation to leaves (leaf mass fraction, efficient construction of leaf surface area (specific leaf area) and biomass growth per unit leaf area (net assimilation rate). This paper shows that trade-offs between investment in carbohydrate reserves and growth occur only among deciduous species, leading to differences in relative contribution made by the underlying components of relative growth rate between the leaf habit groups. The results suggest that differences in drivers of relative growth rate occur among savanna species because these have different selected strategies for coping with fire disturbance in savannas.

 

DEF- and GLO-like proteins may have lost most of their interaction partners during angiosperm evolution
DEFICIENS (DEF)- and GLOBOSA (GLO)-like proteins constitute two groups of floral homeotic transcription factors that were already present in the most recent common ancestor of angiosperms. Together they specify the identity of petals and stamens in flowering plants. This paper strengthens the hypothesis that a reduction in the number of interaction partners of DEF- and GLO-like proteins, with DEF–GLO heterodimers remaining the only DNA-binding dimers in core eudicots, contributing to developmental robustness, canalization of flower development and the diversification of angiosperms.