Molecular mediation of photoperiodic control in activity-dormancy tree growth cycles (Invited Review)
Annals of Botany 120: 351–360, 2017 doi: 10.1093/aob/mcx061
Plants residing in temperate and boreal regions undergo annual activity-dormancy cycles in order to cope with the extreme variations in climate that accompany changes in seasons. Photoperiod and temperature signals act as the key environmental cues controlling growth cessation and dormancy. Maurya and Bhalerao highlight data indicating that symplastic communication may mediate certain aspects of seasonal growth; the results point to a high level of conservation in the signalling pathways that mediate photoperiodic control of seasonal growth in trees and flowering in annual plants such as Arabidopsis. This review article suggests that the future challenge is extending these insights into the control of phenology in model plants such as poplar and spruce by applying a similar framework to other, non-model trees.
Authors: Jay P. Maurya and Rishikesh P. Bhalerao
Mixotrophy in boreal pyroloids does not vary with tissue age or light level
Annals of Botany 120: 361–371, 2017 doi: 10.1093/aob/mcx054
Mixotrophic species obtain their carbon by mixing autotrophy and heterotrophy. Some forest mixotrophs gain their energy and carbon from both photosynthesis and mycorrhizal fungi colonizing their roots; the plasticity of orchids increasing their use of fungal carbon in young shoots (before leaf expansion) and in shaded conditions has been well studied. Lallemand et al. investigate developmental and environmental plasticity of mixotrophy in pyroloids (Pyroleae, Ericaceae) by measuring leaf isotopic abundance and nitrogen content in temperate Boreal forests. The absence of noticeable responses to age or light availability in pyroloids, in contrast to co-occurring orchids, suggests unexpected diversity of mixotrophic nutrition strategies.
Authors: Félix Lallemand, Ülle Puttsepp, Mait Lang, Aarne Luud, Pierre-Emmanuel Courty, Cécile Palancade, and Marc-André Selosse
Does the seed bank contribute to the build-up of a genetic extinction debt for grassland populations of Campanula rotundifolia?
Annals of Botany 120: 373–385, 2017 doi: 10.1093/aob/mcx057
Many plant species manage to postpone eventual local extinction, through longevity-conserving strategies such as building a soil seed bank. Plue et al. test whether seed banks can achieve temporal delays in the loss of genetic diversity that is referred to as a species extinction debt. In fragmented grassland populations of Campanula rotundifolia, genetic diversity today is still at surprisingly high levels despite substantial habitat loss. For populations exhibiting a genetic extinction debt the limited; unique genetic diversity of the seed bank alone seems unable to significantly mitigate or counter the detrimental effects of habitat fragmentation on C. rotundifolia′s population genetic structure.
Authors: Jan Plue, Katrien Vandepitte, Olivier Honnay and Sara A. O. Cousin
Genetic diversity of paper mulberry herbaria samples from the Pacific
Annals of Botany 120: 387–404, 2017 doi: 10.1093/aob/mcx062
Paper mulberry (Broussonetia papyrifera, Moraceae) is a dioecious species native to continental Southeast Asia and East Asia, including Taiwan, that was introduced by humans across the Pacific islands. Payacan et al. analyse the genetic diversity of herbaria specimens of paper mulberry from the Pacific revealing its dispersal history in Oceania, using molecular markers (microsatellites, chloroplast, ribosomal and sex markers). Herbaria provide an overview of the historical geographical range of species before later introductions and local extinctions. 15 genotypes were detected in near and remote Oceanian samples, in spite of the vegetative propagation of B. papyrifera in the Pacific. The pattern linking the genotypes within remote Oceania reflects the importance of central Polynesia as a dispersal hub.
Authors: Claudia Payacan, Ximena Moncada, Gloria Rojas, Andrew Clarke, Kuo-Fang Chung, Robin Allaby, Daniela Seelenfreund, and Andrea Seelenfreund
Effects of changes in leaf properties mediated by methyl jasmonate (MeJA) on foliar absorption of Zn, Mn, and Fe
Annals of Botany 120: 405–415, 2017 doi: 10.1093/aob/mcx063
The mechanisms for the foliar absorption of nutrients are poorly understood, and it has been suggested that leaf properties could potentially have impact upon the foliar absorption of nutrients. Using methyl jasmonate (MeJA) to alter leaf properties, Cui et al. utilize traditional analytical approaches in addition to synchrotron-based X-ray fluorescence microscopy to investigate the absorption of foliar-applied Zn, Mn, and Fe in sunflower (Helianthus annuus), tomato (Solanum lycopersicum), and soybean (Glycine max). They find that the combined thickness of cuticle and epidermal cell wall plays an important role in influencing the absorption of foliar-applied nutrients.
Authors: Cui Li, Peng Wang, Neal W. Menzies, Enzo Lombi, and Peter M. Kopittke
Exploring fungus-plant N transfer in a tripartite ant–plant–fungi mutualism
Annals of Botany 120: 417–426, 2017 doi: 10.1093/aob/mcx064
The ant-plant Hirtella physophora (Chrysobalanaceae), the ant Allomerus decemarticulatus (Myrmicinae) and an Ascomycete fungus, Trimmatostroma sp., form a tripartite association. The fungus improves nutrient uptake by the host plant, but hitherto it has been unclear whether it has an indirect or a direct role in transferring nutrients to the plant. Identification of hyphae inside stem tissue and a stable nitrogen isotope tracer experiment combined with NanoSIMS imaging reveals that 15N-enriched cells are not diffuse. Leroy et al. show that in this ant-plant system a fungus actively transfers nitrogen from a 15N-labelling solution to the plant’s stem tissues, suggesting that the fungus may play a role in transporting nutrient-derived ant waste. The complex trophic structure of ant-plant interactions is shown to rely upon the presence of the fungus. The study provides insight into the potentially important nutritional aspects and tradeoffs involved in myrmecophyte–ant mutualisms.
Authors: Céline Leroy, Alain Jauneau, Yves Martinez, Armelle Cabin-Flaman, David Gibouin, Jérôme Orivel, and Nathalie Séjalon-Delmas
Fusarium wilt of cucumber plants is not caused by water shortage
Annals of Botany 120: 427–436, 2017 doi: 10.1093/aob/mcx065
Fusarium wilted cucumber (Cucumis sativus) plants are associated with water imbalance and leaf wilting. In order to investigate whether Fusarium wilt arises from water shortage, Sun et al. tested physiological responses to water stress and Fusarium infection. Responses of cucumber leaves varied according to the leaf regions affected. Under water stress, the leaf edge was significantly impaired while central sections were less adversely affected. In contrast, FOC infection caused serious membrane damage and higher leaf temperature in the centre. The leaf region responses and different osmotic alteration illustrates the non-causal relationship between Fusarium wilt and water transport blockage.
Authors: Yuming Sun, Min Wang, Yingrui Li, Zechen Gu, Ning Ling, Qirong Shen, and Shiwei Guo
Early Arabidopsis root hair growth stimulation by pathogenic strains of Pseudomonas syringae
Annals of Botany 120: 437–446, 2017 doi: 10.1093/aob/mcx073
The root architecture of Arabidopsis seedlings alters after inoculation with beneficial rhizobacteria in an auxin-dependent manner, resulting in longer root hairs. Surprisingly, Pečenková et al. find that pathogenic Pseudomonas syringae bacteria provoke a similar level of root hair growth stimulation starting several hours after the inoculation. Analyses of root hair lengths of several mutant lines indicate the roles of ethylene signalling and secretory machinery in eliciting root hair growth response. Neither of the known elicitor molecules was able to induce this reaction; however, the range of root hair response could be moderated by pre-treatment with the Flg22 peptide, butsalicylic and jasmonic acid pathways are not involved.
Authors: Tamara Pečenková, Martin Janda, Jitka Ortmannová, Vladimíra Hajná, Zuzanna Stehlíková, and Vicktor Žárský
Unfavourable pollination environments promote evolution of a stable mixed reproductive system in angiosperms
Annals of Botany 120: 447–456, 2017 doi: 10.1093/aob/mcx059
Recent theoretical studies have shown that mixed reproductive systems in angiosperms can be stable, but empirical data to confirm this hypothesis are still scarce. Arista et al. study four populations of Hypochaeris salzmanniana (Asteraceae) during two consecutive years and find that self-compatibility increases when the pollination environment is uncertain, conferring reproductive assurance when pollinator attendance is low. The mixed reproductive system of H. salzmanniana appears to be an evolutionarily stable strategy, with year-to-year changes in self-incompatibility expression deriving directly from the balance between reproductive assurance and inbreeding depression.
Authors: Montserrat Arista, Regina Berjano, Juan Viruel, María Á. Ortiz, María Talavera, and Pedro L. Ortiz
Deep rooting in a wheat doubled haploid population with wild emmer introgression
Annals of Botany 120: 457–470, 2017 doi: 10.1093/aob/mcx068
The genetic basis of increased rooting below the plough layer, post-anthesis in the field, of an elite wheat line (Triticum aestivum cv. Shamrock) with recent introgression from wild emmer (T. dicoccoides), is here investigated. Drought post-anthesis severely affects bread wheat yields as grain set and grain filling are compromised; increasing the proportion of root systems reaching deeper soil layers improves the crop’s access to subsoil water at later growth stages and directly impacts yield. A linkage map was produced using single nucleotide polymorphism markers to identify quantitative trait loci (QTL) for rooting traits. Clarke et al. find significant genetic diversity in a doubled haploid wheat population for field root length density at anthesis. Wild emmer introgressions were found to influence rooting ability both in the field and in controlled environment conditions. Identifying genetic controls for rooting at depth in the field environment is important for wheat breeders aiming for more efficient root distribution in the soil profile.
Authors: Christina K. Clarke, Peter J. Gregory, Martin Lukac, Amanda J. Burridge, Alexandra M. Allen, Keith J. Edwards, and Mike J. Gooding
Floral scent variation in woodland stars
Annals of Botany 120: 471–478, 2017 doi: 10.1093/aob/mcx069
The evolution of floral scent has recently emerged as a major topic in plant research with several studies focused upon the implications of floral chemistry for fitness and diversification. Friberg et al. disentangle the genetic and environmental components underlying floral scent variation in the woodland star, Lithophragma bolanderi (Saxifragaceae), testing if the release of floral volatiles depends on nutrient availability. Great similarity in floral scent resulted from growing genetically identical clones in two different nutrient treatments, but very different scent distinguished clonal pairs, implying a strong genetic component to floral scent variation.
Authors: Magne Friberg, Mia T. Waters, and John N. Thompson
Temporal sensitivity of wheat seed quality to extreme temperature
Annals of Botany 120: 479–493, 2017 doi: 10.1093/aob/mcx074
Brief periods of extreme temperature are associated with climate change and can damage plants at sensitive developmental stages. Nasehzadeh and Ellis analyse the effects of extreme temperature during wheat seed development and maturation to identify temporal variation in sensitivity of diverse traits: earlier in development for seed weight and certain aspects of bread quality, such as protein content and later in maturation for traits such as Hagberg falling number, a measure of protein quality, or for seed longevity. Longevity was affected positively by high temperature late in maturation, but negatively early in seed development. These subtle, diverse climate change impacts indicate that short periods of extreme temperature may affect wild species’ adaptation and competitiveness, affecting a crop’s value for sowing, human nutrition, and food processing purposes.
Authors: M. Nasehzadeh and R.H. Ellis