Aluminium accumulation and XET action in bean root tips
Two genes PvXTH9 and PvXTHb have been suggested to regulate the polyethylene glycol-reduced cell-wall Al accumulation in root tips. Through the spatial and temporal analysis of Al-inhibited root elongation, Al accumulation, XTH genes expression and XET enzyme action in root tips, Zhang et al. (pp. 1–9) further demonstrated the regulatory role of XTH genes and XET enzyme in cell-wall Al accumulation. The results provide novel insights into the physiological and molecular mechanisms of cell-wall structure modification as a response of plant roots to osmotic stress that will assist mitigation of Al and drought stresses severely limiting crop yields on acid soils.
Arbuscular mycorrhizal growth responses and phosphorous efficiency in soybean genotypes
Arbuscular mycorrhizal (AM) fungi play a key role in phosphate (P) uptake of many crop species, but the mechanisms by which P uptake in the AM symbiosis is controlled are only poorly understood. Wang et al. (pp. 11–21) examined the effects of the phosphate acquisition efficiency (PAE) of soybean plants on P uptake and transport via the plant and mycorrhizal uptake pathway and demonstrate here that also soybeans with a higher PAE can highly benefit from an AM symbiosis, and that mycorrhizal P uptake benefits are much more determined by the AM fungal species than by the PAE of the host.
Plant design is affected by neighbourhood structure and light availability
Although neighbourhood structure and light availability are recognized as factors that limit survival and species coexistence, its relative importance on plant design is not well understood. Guzmán and Cordero (pp. 23–34) investigate the effect of these factors on biomechanics, allometry, branching and slenderness as properties of the plant design. They found that interference and size of the neighbourhood increase the density-specific stiffness and decrease the developmental stability, while the light availability decreases the branching and increases the slenderness. Because of this, the design must be considered as a key factor that contributes to the adaptation and coexistence in forest communities.
Phylogeny of chili peppers and wild relatives
Sweet and hot chili peppers and their wild relatives (Capsicum spp., Solanaceae) are native to the tropical and temperate Americas. Despite their worldwide importance, Capsicum taxonomy and phylogeny have been only partially analysed to date. Carrizo García et al.. (pp. 35–51) explore the phylogenetic relationships between nearly all Capsicum species and analyse the evolution of key characters and the geographic diversification of the genus. The most comprehensive scheme of Capsicum interspecific relationships is presented, giving new insights about species affinities and the geographic origin of the genus.
History of the zucchini squash
Summer squash, the young fruits of Cucurbita pepo, are a common, high-value fruit vegetable. Of the summer squash cultivar-groups, the zucchini is today the most cosmopolitan but it is also the newest, having been traced to Milan, 1901. Lust and Paris (pp. 53–69) collected and searched books on agriculture and cookery dating from the sixteenth to nineteenth centuries to follow the horticultural development and culinary use of young Cucurbita fruits in Italy. By 1600, round and elongate young fruits of C. pepo were addressed as separate cookery items in Italian kitchens. These elongate squash probably refer to the cocozelles of southern and central Italy. The agricultural books by Cantoni (1855) and Tamaro (1892) suggest that the other elongate Italian squash, the zucchini, originated in northern Italy during the mid-nineteenth century.
A genetic linkage map of perennial ryegrass (Lolium perenne) based on GBS
Genetic linkage maps remain very important tools for gene discovery in many plant species. Whilst several genetic maps exist for perennial ryegrass, it has been difficult to integrate data across studies because of a lack of a reference genome sequence and common genetic markers. Velmurugan et al. (pp. 71–87) have developed a dense SNP-based genetic map of a reference mapping population of ryegrass using genotyping-by-sequencing. All markers on the genetic map are anchored to a draft genome sequence of one of the grandparents of the F2 population; thus future genetics studies using the population will be comparable.
Orchid conservation: further links
Fay (pp. 89–91) introduces the often complex interactions of orchids with mycorrhizal fungi, pollinators and host trees, considering also threats from human utilization and changing land use. The Orchidaceae present particular challenges for conservation. Furthermore, orchids, as one of the largest families of angiosperms ( >26 000 species, species complexes and frequent hybrid formation) are complex to catalogue. Orchids are a fascinating subject for fundamental research with rapid species evolution, specific organ structure and development, but they also suffer from high levels of threat. Effective orchid conservation must take account of the beneficial interactions with fungi and pollinators and the potentially detrimental effects of over-collection and changes in land use.
Commonness, reproductive patterns and inbreeding depression of two Jumellea species
Population size reduction can threaten long-term persistence of plant populations through loss of genetic diversity and inbreeding depression. Blambert et al. (pp. 93–103) evaluate the consequences of population size reduction by comparing mating patterns, levels of genetic diversity and inbreeding depression of the rare and fragmented Jumellea fragrans and the widespread J. rossii. Population size reduction had a negative impact on genetic diversity of J. fragrans, but factors such as mating system or population history can limit the effects.
Mycorrhizal associations in recently diverged Epipactis species
In orchid species that have populations occurring in strongly contrasting habitats, mycorrhizal divergence and other habitat-specific adaptations may lead to the formation of reproductively isolated taxa and ultimately to species formation. In this study, Jacquemyn et al. (pp. 105–114) used 454 amplicon pyrosequencing to investigate mycorrhizal communities associating with Epipactis helleborine in its typical forest habitat and with its presumed sister species E. neerlandica that almost exclusively occurs in coastal dune habitats. E. helleborine and E. neerlandica associated with strongly divergent mycorrhizal communities, so detailed experiments on habitat-specific adaptations in general and mycorrhizal divergence to the process of speciation in orchids are required.
Temporal dynamics of Corsican orchid communities
Orchids are particularly sensitive to environmental changes due to their narrow ranges in secondary-successional habitats, and partially cryptic which impede the observation during monitoring. Here Vogt-Schilb et al. (pp. 115–123) investigated how habitat change can impact orchid spatio-temporal distributions in Corsica, while taking into account imperfect detection. Two field surveys conducted 27 years apart (1982–1984 vs. 2009–2011) at the same 45 sites in Corsica show contrasting patterns in orchid dynamics at different spatial scales; while marked turnover of species composition was revealed locally, the regional species pool was maintained despite an overall increase in woody plant cover. The existing landscape mosaics of different ecologies maintain diversity at larger spatial scales. Furthermore, the study revealed great variation in detectabilities among orchid species and thus confirmed the relevancy of site-occupancy models accounting for imperfect detection.
Strengthening the taxonomic backbone of Thai orchid conservation
Pedersen et al. (pp. 125–133) present analyses of morphometric and AFLP data from populations of Geodorum (Orchidaceae) – a study conducted in preparation of the Flora of Thailand account. Patterns of phenetic variation and inferred hierarchical genetic differentiation suggest that G. pulchellum sensu Seidenf./G. siamense should be treated as one variable species (meaning that the allegedly rare G. pulchellum sensu Seidenf. should not be given independent conservation priority). Well-supported classifications are crucial for conservation planning, and this study demonstrates that flora accounts can benefit from prior analytical approaches to intricate species complexes.
Floral scent chemistry in the orchid genus Gongora
Floral scent is a key component of pollinator attraction and its chemistry modulates pollinator behavior and the formation of plant-pollinator networks. Neotropical Gongora orchids exhibit specialized pollinator associations with male euglossine bees, in which male bees visit orchid flowers to collect volatile chemicals that they store in hind-leg pouches to subsequently use during courtship display. Hence, Gongora floral scent compounds simultaneously serve as signaling molecules and pollinator rewards. Hetherington-Rauth & Ramírez (pp. 135–148) conducted a comparative analysis of floral scent across the genus showing that scent molecules are largely species specific and qualitatively and quantitatively divergent among closely related taxa.
Relationship between soil nutrients and orchid mycorrhizal associations
Mycorrhizal associations are known to be influenced by soil nutrient availability but have been poorly studied in orchids. Mujica et al. (pp. 149–158) studied two terrestrial orchids of the genus Bipinnula from central Chile across a soil nutrient gradient. They found a significant relationship between soil nutrients and composition, taxonomic richness and phylogenetic diversity of mycorrhizal fungi, which supports the hypothesis that specialization is favored under high soil nutrient availability. Their findings help understand factors that promote the evolution of ecological specialization, a major question for evolutionary biologists since Charles Darwin.
Sexual and asexual reproduction in a mycoheterotrophic orchid
Sexual reproduction is common within Orchidaceae, though apomixis does occur in some genera allowing them to produce seeds that are clones of the mother. The reproductive embryology of mycoheterotrophic plants remains under-studied. Krawczyk et al. (pp. 159–172) provide evidence for the co-occurrence of sexual and apomictic reproduction in a population of mycoheterotrophic plants: Epipogium aphyllum. The authors investigated reproduction capability via open pollination, induced autogamy, autogamy sensu stricto, and autonomous apomixis. They report that although sexual reproduction dominates, incidental parthenogenesis is much more likely than natural self-fertilization, which is rare or unlikely. These findings suggest that E. aphyllum has the potential to produce seeds via both sexual and asexual means.