Intraspecific floral scent variation in the context of evolutionary ecology (Review)
Annals of Botany 120: pp. , 2017 doi: 10.1093/aob/mcx055
Floral scents attract pollinators, and a varied repertoire of floral scents has been documented among plant species. Delle-Vedove et al. survey the results of 81 studies investigating intraspecific variation of floral scents in 132 taxa. Variation was classified according to identity, proportion or absolute quantities of Volatile Organic Compounds, as well as data with the potential to explain variation, such as methodology, plant origin or pollination biology. Variation was evident in almost all investigated species, both among individuals (among and sometimes within populations) and within individuals across different temporal scales. This review article suggests that floral scent variation can be mediated by temporal shifts in pollinator identity and behaviour among populations, deceit pollination and sex-specific selection, and also by natural enemies, genetic drift, gene migration and other constraints.
Authors: Roxane Delle-Vedove, Bertrand Schatz and Mathilde Dufay
The intricate intracellular structure of a rice mesophyll cell
Annals of Botany 120: pp. , 2017 doi: 10.1093/aob/mcx036
Rice (Oryza sativa) leaf blades possess lobed mesophyll cells with intricate cell boundaries. Their sub-cellular structure has been observed with transmission electron microscopy (TEM) of thin sections, but the whole three-dimensional (3D) structure has not been reconstructed. Oi et al. examine whole rice mesophyll cells using a Focus Ion Beam Scanning Electron Microscope (FIB-SEM). The 3-D reconstructed cell models were discoid-shaped, comprising several lobes around the cell periphery, with chloroplasts spread as sheets along the cell lobes and occupying half of the cell volume. The cell shape and chloroplast distribution enhances the leaf area available for CO2 absorption.
Authors: Takao Oi, Sakiko Enomoto, Tomoyo Nakao, Shigeo Arai, Koji Yamane and Mitsutaka Taniguchi.
Stress or Strain Gradient Hypothesis?
Annals of Botany 120: pp. , 2017 doi: 10.1093/aob/mcx037
The Stress Gradient Hypothesis (SGH) proposes that competition prevails in undisturbed and productive environments, and shifts to facilitation in disturbed or stressful environments. Yet the environmental condition where facilitation or competition prevails is highly debated. Liancourt et al. investigate variation in plant interactions, by analysing how Caragana versicolor species and associated community perceive and respond to the ambient level of stress, over the species’ entire elevation range in the arid Trans-Himalayas. The authors propose a double-sided interpretation of SGH: the Stress Gradient Hypothesis that predicts where facilitation should prevail at the community level and, on the other side of the coin, the Strain Gradient Hypothesis that predicts where facilitation should prevail within the niche of a particular species.
Authors: Pierre Liancourt, Yoann Le Bagousse-Pinguet, Christian Rixen and Jiri Dolezal
Evolution of UV floral patterning in sunflowers
Annals of Botany 120: pp. , 2017 doi: 10.1093/aob/mcx038
Ultraviolet (UV) floral patterning varies both intra- and interspecifically in sunflowers and many other plant species. It impacts upon pollinator attraction and can be critical to reproductive success and crop yields. Using UV photography and genotyping-by-sequencing, Moyers et al. identify quantitative trait loci (QTL) for floral UV patterning in an intraspecific cross of the sunflower Helianthus argophyllus, a close relative of the domesticated sunflower. Proportional UV bullseye size is shown to be phenotypically correlated but genetically independent, and so should be able to respond to natural or artificial selection independently. The identified QTL facilitate predictions of proportional and absolute sizing of UV pigmentation in natural populations. In the context of crop species, the authors note that proportional UV pigmentation could be modified without affecting flowerhead size, a critical trait in domestic sunflowers.
Authors: Brook T. Moyers, Gregory L. Owens, Gregory J. Baute and Loren H. Rieseberg.
Evolving towards introgression: hybridization and hybrid swarms
Annals of Botany 120: pp. , 2017 doi: 10.1093/aob/mcx039
The extent to which hybridization leads to gene flow between plant species depends on the structure of hybrid populations. To assess possible variation in a hybrid population structure, Yan et al. evaluate magnitude and direction of natural hybridization between two diploid Chinese endemic species Rhododendron spiciferum and R. spinuliferum. Thirteen nuclear microsatellites and cpDNA trnL-F were employed to characterize the genetic structure of 566 individuals collected from 15 non-allopatric populations and nine allopatric parental populations. Gene flow between R. sjpiciferum and R. spinuliferum is found to be bidirectional and asymmetric in some hybrid swarms. Introgression, rather than hybrid speciation, is a more likely outcome of hybridization between these hybridizing taxa.
Authors: Li-Jun Yan, Kevin S. Burgess, Richard Milne, Chao-Nan Fu, De-Zhu Li and Lian-Ming Gao.
Reproductive strategy of a lichenized fungus shifts along a climatic gradient
Annals of Botany 120: pp. , 2017 doi: 10.1093/aob/mcx045
Life history theory predicts that plants in adverse environments for juvenile performance start reproduction at a smaller size and exhibit higher reproductive allocation compared to their counterparts in more favourable environments. Merinero et al. explore the reproductive strategy of an asexually reproducing lichen along a rainfall gradient. Consistent with the predictions of life-history theory, they find a decrease in the size for reproduction, and a higher reproductive allocation in drier, adverse, environments. By focusing on an asexually reproducing lichen, the study improves our understanding of life history diversity and reproductive strategies across environments.
Authors: Sonia Merinero, Marcos Méndez, Gregorio Aragón and Isabel Martínez.
Apoplastic barriers in maize lateral roots: root heterogeneity and developmental plasticity
Annals of Botany 120: pp. , 2017 doi: 10.1093/aob/mcx047
Roots rely on apoplastic barriers for nutrient absorption. However, little is known about the establishment of these barriers within the lateral roots. The branching, permeability of the outer cell layers and differentiation of the endo- and exodermis are studied in primary roots and various laterals of Zea mays under different stress factors of agronomic importance (salinity, heavy metal toxicity, hypoxia, etc.). Tylová et al. propose that fine laterals represent portions of a complex root system with a less advanced state of endodermis and exodermis differentiation, but with substantial ability to modify maturation of exodermis in response to environmental conditions. Branching and establishment of barriers in fine laterals may be at the crux of the root system - rhizosphere interaction.
Authors: Edita Tylová, Eva Pecková, Zuzana Blascheová and Aleš Soukup.
Genetics of phenotypic plasticity and biomass traits in hybrid willows
Annals of Botany 120: pp. , 2017 doi: 10.1093/aob/mcx029
Phenotypic plasticity can have a great impact on the distribution of taxa and the productivity of crops across contrasting environments. Berlin et al. study the genetic architecture of biomass traits, including phenotypic plasticity in an experimental hybrid willow (Salix) population. The population was planted over three common garden experiments, comprising one climatic contrast between Sweden and Italy and one water availability contrast in Italy. Compared to phenological traits, the genetic regulation of biomass traits was highly sensitive to the climate. These important findings demonstrate that breeding systems should be adapted according to climate in order to maximise biomass production in willows.
Authors: S. Berlin, H.R. Hallingbäck, F. Beyer, N-E. Nordh, M. Weih and A. C. Rönnberg-Wästljung.
Ethylene perception determines tomato plant growth induction by soil bacteria
Annals of Botany 120: pp. , 2017 doi: 10.1093/aob/mcx052
Plant-growth-promoting bacteria (PGPB) are soil microorganisms able to interact with plants and stimulate their growth, positively affecting plant physiology and development. Ethylene is involved in plant development and abiotic response. Ibort et al. investigate whether ethylene perception is critical for plant-bacteria interaction and growth induction by assessing Inoculation effects of two PGPB strains (unable to produce and degrade ethylene) regarding ethylene sensitivity in tomato (Solanum lycopersicum) plants at juvenile and mature stages. Ethylene sensitivity is shown to be a determinant for Bacillus megaterium, but not involved in Enterobacter C7 promotion activity. The insights gained into PGPB effects on plant growth and physiology could have applications for agriculture, reducing use of chemicals and improving resource use and crop production.
Authors: P. Ibort, S. Molina, R. Núñez, A. M. Zamarreño, J. M. García-Mina, J. M. Ruiz-Lozano, M. C. Orozco-Mosqueda, B. R. Glick and R. Aroca
Climate affects hydraulic and stomatal traits
Annals of Botany 120: pp. , 2017 doi: 10.1093/aob/mcx020
Hydraulic traits influence the ability of plant species to grow and survive in water-limited environments. Bourne et al. compare hydraulic, anatomical, stomatal and leaf tissue water relations traits in six Eucalyptus species trees grown in a common garden plot; by focusing the study on a single genus, much of the variation that could be attributed to different climatic or environmental characteristics is eliminated. The nature of xylem traits in Eucalyptus trees was found to be genetically constrained with important implications for the limits of species‘ responses to changing environmental conditions and thus for species survival and distribution into the future.
Authors: Aimee E. Bourne, Danielle Creek, Jennifer M. R. Peters, David S. Ellsworth and Brendan Choat.
Reciprocal sowing experiment shows local adaptation and phenotypic plasticity
Annals of Botany 120: pp. , 2017 doi: 10.1093/aob/mcx046
Reciprocal sowing experiments along environmental gradients allow evaluating local adaptation and phenotypic plasticity as in situ mechanisms to cope with climate change. Sánchezet al. used this approach to infer the adaptive potential of five gypsum specialist shrubs to increasing aridity in central Spain. As no evidence of local adaptation was detected, the stress-tolerant and plastic response exhibited by seed and seedlings may be the only features that will allow gypsophytes to cope with climate change in their island-like habitats.
Authors: A. M. Sánchez, P. Alonso-Valiente, M. J. Albert and A. Escudero.
Shade tolerance, fruiting phenology and Janzen-Connell effects in Amazonian palms
Annals of Botany 120: pp. , 2017 doi: 10.1093/aob/mcx051
The Janzen-Connell (JC) hypothesis proposes that individual plants of the same tropical rainforest tree species are more likely to attract specialist natural enemies when they grow close together, thereby resulting in community-level diversity. Choo et al. study two Neotropical palm species (Astrocaryum murmuru and Attalea phalerata) using seed predation experiments and spatial analyses. They show that variation in the strength of JC effects across life-stages is consistent with differences in shade-tolerance and fruiting phenology across species. The authors infer that differences in these life history traits may also help explain variation in the strength of JC effects across whole communities.
Authors: Juanita Choo, Cecilia Carasco, Patricia Alvarez-Loayza, B. Beryl Simpson and Evan P. Economo.
Responses of lichen communities to 18 years of natural and experimental warming
Annals of Botany 120: pp. , 2017 doi: 10.1093/aob/mcx053
Climate change and warming is expected to have major impacts on alpine and arctic ecosystems. Alatalo et al. describe the effects of 18 years of ambient and experimental warming, with total mean annual temperature increase of 2 °C, on lichens in two alpine plant communities. Lichen cover increased in heath under ambient conditions, but remained stable under experimental warming. Species richness and effective number of species decreased under experimental warming in meadow environments. Lichen community parameters were all negatively correlated with plant canopy cover. These long-term data show that both biotic and abiotic factors modify the impacts of climate change on lichens.
Authors: Juha M. Alatalo, Annika K. Jägerbrand, Shengbin Chen and Ulf Molau
Potential benefits of flood-induced adventitious roots depend on duration of submergence
Annals of Botany 120: pp. , 2017 doi: 10.1093/aob/mcx049
The formation of aquatic adventitious roots (ARs) is considered an important adaptation to the adverse conditions of flooding. These roots replace the original root system, the growth of which is inhibited by oxygen deficiency in the flooded soil. New ARs are supposed to increase fitness during flooding by improving nutrient uptake. However, they may also incur costs to the plant’s energy and carbohydrate budget. Zhang et al. show that the balance between the potential benefits and costs depends on the duration of partial flooding in Solanum dulcamara (Bittersweet). Net benefits were found in long-term but not in short-term flooding, indicating an adaptive role of ARs only during long-term flooding.
Authors: Qian Zhang, Heidrun Huber, Simone J. M. Beljaars, Diana Birnbaum, Sander de Best, Hans de Kroon and Eric J. W. Visser
