The link between selfing and greater dispersibility in a heterocarpic Asteraceae

PREMISE OF THE STUDY

Although an evolutionary link between breeding system and dispersibility has been proposed, to date empirical data and theoretical models of plants show contrasting trends.

METHODS

We tested two competing hypotheses for the association between breeding systems and dispersibility in the heterocarpic Hypochaeris salzmanniana (Asteraceae) by using both an experimental approach and surveys over 2 years of five natural populations along an environmental cline with a gradient of pollinator availability.

KEY RESULTS

Hypochaeris salzmanniana produced two types of fruits, beaked (BF) and nonbeaked (NBF), which differ in their dispersal ability. The BF were lighter and had a lower dropping velocity and higher dispersal distance than the NBF. Potential for long-distance dispersal, measured as BF ratio per head, had high narrow-sense heritability. Greater dispersibility and selfing ability were linked at all the scales studied. Both selfed BF and NBF fruits had longer plumes and lower plume loading than outcrossed fruits, characteristics that promote farther dispersal. Natural populations with a higher percentage of self-compatible plants showed a higher BF ratio. Moreover, selfing led to a higher BF ratio than outcrossing.

CONCLUSIONS

The avoidance of inbreeding depression seems to be the most plausible selective pressure for the greater dispersibility traits of selfed seeds. Furthermore, the ability to modulate the BF ratio and thus the potential for long-distance dispersal of offspring based on its selfed or outcrossed origin could be advantageous, and therefore selected, under unpredictable pollination environments that favor higher dispersive selfers, which overcome both pollen limitation and inbreeding avoidance.

Supplemental LED inter-lighting compensates for a shortage of light for plant growth and yield under the lack of sunshine

Supplemental lighting can enhance yield when sunlight is limited, as in winter. As the effect of frequent cloudy or rainy days in other seasons on plant growth and yield remains unclear, we investigated the effect on tomato (Solanum lycopersicum) and compensation by supplemental LED inter-lighting. Plants were grown under 30% shade cloth on 0%, 40%, or 60% of days. Lower leaves were illuminated with red and blue LED inter-lighting modules from right after first anthesis, or not illuminated. Shading during 40% and 60% of days diminished daily light integral (DLI) by 26% and 40%, respectively, and reduced shoot dry weight by 22.0% and 23.3%, yield by 18.5% and 23.3%, and fruit soluble solids content by 12.3% and 9.3%. In contrast, supplemental inter-lighting improved the light distribution within plants and compensated DLI, and maintained similar yield and soluble solids content in both shade treatments as in the control. These results clearly show that supplemental LED inter-lighting could efficiently compensate for a shortage of light for plant growth, photosynthesis and thus yield under the lack of sunshine.

Anatomical structure of Camellia oleifera shell

The main product of Camellia oleifera is edible oil made from the seeds, but huge quantities of agro-waste are produced in the form of shells. The primary components of C. oleifera fruit shell are cellulose, hemicellulose, and lignin, which probably make it a good eco-friendly non-wood material. Understanding the structure of the shell is however a prerequisite to making full use of it. The anatomical structure of C. oleifera fruit shells was investigated from macroscopic to ultrastructural scale by stereoscopic, optical, and scanning electron microscopy. The main cell morphology in the different parts of the shell was observed and measured using the tissue segregation method. The density of the cross section of the shell was also obtained using an X-ray CT scanner to check the change in texture. The C. oleifera fruit pericarp was made up of exocarp, mesocarp, and endocarp. The main types of exocarp cells were stone cells, spiral vessels, and parenchyma cells. The mesocarp accounted for most of the shell and consisted of parenchyma, tracheids, and some stone cells. The endocarp was basically made up of cells with a thickened cell wall that were modified tracheid or parenchyma cells with secondary wall thickening. The most important ultrastructure in these cells was the pits in the cell wall of stone and vessel cells that give the shell a conducting, mechanical, and protective role. The density of the shell gradually decreased from exocarp to endocarp. Tracheid cells are one of the main cell types in the shell, but their low slenderness (length to width) ratio makes them unsuitable for the manufacture of paper. Further research should be conducted on composite shell-plastic panels (or other reinforced materials) to make better use of this agro-waste.

Can you make morphometrics work when you know the right answer? Pick and mix approaches for apple identification

Morphological classification of living things has challenged science for several centuries and has led to a wide range of objective morphometric approaches in data gathering and analysis. In this paper we explore those methods using apple cultivars, a model biological system in which discrete groups are pre-defined but in which there is a high level of overall morphological similarity. The effectiveness of morphometric techniques in discovering the groups is evaluated using statistical learning tools. No one technique proved optimal in classification on every occasion, linear morphometric techniques slightly out-performing geometric (72.6% accuracy on test set versus 66.7%). The combined use of these techniques with post-hoc knowledge of their individual successes with particular cultivars achieves a notably higher classification accuracy (77.8%). From this we conclude that even with pre-determined discrete categories, a range of approaches is needed where those categories are intrinsically similar to each other, and we raise the question of whether in studies where potentially continuous natural variation is being categorised the level of match between categories is routinely set too high.

Localization of phenolic compounds in the fruits of Silybum marianum characterized by different silymarin chemotype and altered colour

Silybum marianum (L.) Gaertn (Asteraceae) is a valuable medicinal plant utilized for silymarin production. However, only fragmentary and contradictory information about silymarin localization within S. marianum fruit are available. In this work, a twofold research approach was adopted in order to investigate the distribution and quantification of silymarin and of other phenolic compounds within the different fruit regions (pericarp, seed integument, cotyledon). Two S. marianum wild accessions with contrasting silymarin chemotype (A and B) and a mutant line (C) with an altered fruit colour were analysed. Fruits of Cynara cardunculus were studied as a reference. Firstly, the fruit morpho-anatomy was reviewed by means of light microscopy digital imaging and, secondly, a comprehensive histolocalization of the different classes of polyphenols within the fruit was carried out. The experimental evidences confirmed that silymarin, and its precursor taxifolin, are only accumulated in the seed integuments. The dark colour of fully-ripened fruits is due to the accumulation of condensed tannins in the pericarp subepidermal cell layer. On the contrary, the studied mutant line shows reduced condensed tannin content that probably result from impairment at the level of flavonoid biosynthetic pathway. Condensed tannins content is comparatively low in S. marianum fruits and very low in the identified mutant line. This could represent an advantage for the possible employment of S. marianum fruits and of silymarin extraction by-products in the feed and food sector.

Influence of natural variation in berry size on the volatile profiles of Vitis vinifera L. cv. Merlot and Cabernet Gernischt grapes

This study was conducted during the 2014 and 2015 vintages on Vitis vinifera L. cv. Merlot and Cabernet Gernischt to investigate whether natural variation in berry size could affect grape aromatic compounds. Grape berries were separated into three size categories based on their diameter: small, middle and large. The results showed that berry size exerted a significant influence on the volatile profiles of both winegrape varieties. Hierarchical clustering analysis demonstrated that the volatile profiles of middle berries were different from those of large and small berries. Middle berries had the greatest abundance of aroma compounds, followed by small and large berries. Especially, C6/C9 compounds, norisoprenoids, terpenoids showed markedly different concentrations among differently sized Merlot berries and C6/C9 compounds, terpenoids among differently sized Cabernet Gernischt berries. Middle berries of both grape varieties may possess the greatest intensity of fresh-green, fruity and floral aromas due to the high odour activity values (OAVs) of decanal, hexanal, (E)-2-hexenal, (E)-β-damascenone and β-ionone in middle sizes of Merlot berries and the high OAVs of (E)-2-hexenal and (E)-β-damascenone in middle sizes of Cabernet Gernischt berries. This knowledge could be important for winemakers to conduct targeted berry sorting, thereby improving the aromatic quality of grapes.

The critical role of fossils in inferring deep-node phylogenetic relationships and macroevolutionary patterns in Cornales

PREMISE OF THE STUDY

The basal asterid order, Cornales, experienced a rapid radiation during the Cretaceous, which has made it difficult to elucidate the early evolution of the order using extant taxa only. Recent paleobotanical studies, however, have begun to shed light on the early diversification of Cornales. Herein, fossils are directly incorporated in phylogenetic and quantitative morphological analyses to reconstruct early cornalean evolution.

METHODS

A morphological matrix of 77 fruit characters and 58 taxa (24 extinct) was assembled. Parsimony analyses including and excluding fossils were conducted. A fossil inclusive tree was time-scaled to visualize the timing of the initial cornalean radiation. Disparity analyses were utilized to infer the morphological evolution of cornaleans with drupaceous fruits.

KEY RESULTS

Fossil inclusive and exclusive parsimony analyses resulted in well-resolved deep-node relationships within Cornales. Resolution in the fossil inclusive analysis is substantially higher, revealing a basal grade including Loasaceae, Hydrangeaceae, Hydrostachyaceae, Grubbiaceae, a Hironoia+Amersinia clade, and Curtisiaceae, respectively, that leads to a "core" group containing a clade comprising a Cretaceous grade leading to clade of Nyssaceae, Mastixiaceae, and Davidiaceae that is sister to a Cornaceae+Alangiaceae clade. The time-scaled tree indicates that the initial cornalean diversification occurred before 89.8 Ma. Disparity analyses suggest the morphological diversity of Cornales peaked during the Paleogene.

CONCLUSIONS

Phylogenetic analyses clearly demonstrate that novel character mosaics of Cretaceous cornaleans play a critical role in resolving deep-node relationships within Cornales. The post-Cretaceous increase of cornalean disparity is associated with a shift in morphospace occupation, which can be explained from ecological and developmental perspectives.

A multi-level test of the seed number/size trade-off in two Scandinavian communities

Seed size is a fundamental life-history trait for plants. A seed number/size trade-off is assumed because the resources invested in reproduction are limited; however, such a trade-off is not always observed. This could be a consequence of the method used for testing it, where the null hypothesis is dictated by common statistical practice, rather than being based on any underlying theory. Alternatively, there might be some population- and species-dependent variables that affect resource availability and, in turn, influence the presence and intensity of this trade-off. Using data on 42 herbs from two communities (lowland and alpine) from Southern Norway, we tested the validity of the classical linear model vs. two previously proposed models, based on resource competition, when assessing the existence of this trade-off at different levels. We also evaluated whether some species- (fruit aggregation, ovules/flower) and population-dependent (pollen limitation) variables could affect this trade-off. Classical linear modelling outperformed the other proposed functional models. Significant seed number/size relationships were negative in single-fruited species, whereas they were positive in species with infructescences of one-seeded fruits. Concordantly, fruit organization was the most influencing variable for the intra-specific trade-off in the lowland community. In the alpine community, species suffering higher pollen limitation showed more strongly negative slopes between seed size and seed number at the fruit/infructescence level. Across species, seed size and number were negatively related, although the relationship was significant in only one of the communities. No evidence of trade-off was found at the plant level. Linear models provide a flexible framework that allows coping with the variability in the seed number/size relationship. The emergence of the intra-specific relationship between seed number and size depends on species- and population-dependent variables, related to resource allocation and the pollination environment.

The pomegranate (Punica granatum L.) genome provides insights into fruit quality and ovule developmental biology

Pomegranate (Punica granatum L.) has an ancient cultivation history and has become an emerging profitable fruit crop due to its attractive features such as the bright red appearance and the high abundance of medicinally valuable ellagitannin-based compounds in its peel and aril. However, the limited genomic resources have restricted further elucidation of genetics and evolution of these interesting traits. Here, we report a 274-Mb high-quality draft pomegranate genome sequence, which covers approximately 81.5% of the estimated 336-Mb genome, consists of 2177 scaffolds with an N50 size of 1.7 Mb and contains 30 903 genes. Phylogenomic analysis supported that pomegranate belongs to the Lythraceae family rather than the monogeneric Punicaceae family, and comparative analyses showed that pomegranate and Eucalyptus grandis share the paleotetraploidy event. Integrated genomic and transcriptomic analyses provided insights into the molecular mechanisms underlying the biosynthesis of ellagitannin-based compounds, the colour formation in both peels and arils during pomegranate fruit development, and the unique ovule development processes that are characteristic of pomegranate. This genome sequence provides an important resource to expand our understanding of some unique biological processes and to facilitate both comparative biology studies and crop breeding.

Associated morphometric and geospatial differentiation among 98 species of stone oaks (Lithocarpus)

Two fruit types can be distinguished among stone oaks (Lithocarpus) species: the ‘acorn’ (AC) and the ‘enclosed receptacle’ (ER) types. Our morphometric analysis of 595 nuts from 98 species (one third of all Lithocarpus spp.) found substantial transition in mechanical protection of the seed between two woody fruit tissues (exocarp and receptacle) of two fruit types. AC fruits were smaller in seed and fruit size and the thin brittle exocarp largely enclosed the seed, whereas ER fruits were larger and the seed was mostly enclosed by thick woody receptacle tissue. The differences in these two tissues were considerably greater between compared to within fruit type and species. Geospatial distribution showed that seed size of all examined species increased with elevation and decreased with latitude, the physical defense increased with both elevation and latitude, and ER-fruit species were more common at higher elevation. The two fruit types represent distinct suites of associated traits that respond differently to the various biotic and abiotic factors associated with geographic variation, profoundly impacting the evolution of the two fruit types. The co-occurrence of two fruit types in the same forest could be a consequence of distinct fruit and animal interactions.

Silencing GRAS2 reduces fruit weight in tomato

GRAS family transcription factors are involved in multiple biological processes in plants. Here, we report that GRAS2 plays a vital role in regulating fruit weight in tomato (Solanum lycopersicum). We establish that the expression of GRAS2 was elevated in ovaries and maintained at a constant level in fertilized ovules. Reduction of GRAS2 expression in transgenic plants reduced fruit weight through modulating ovary growth and cell size. At the metabolic level, downregulation of GRAS2 decreased activities of the gibberellic acid biosynthesis and signal transduction pathways, leading to insufficient levels of active gibberellic acid during the initial ovary development of tomato. Moreover, genotypic diversity of GRAS2 was consistent with the molecular basis of fruit weight evolution, suggesting that GRAS2 contributes to the molecular basis of the evolution of fruit weight in tomato. Collectively, these findings enhance our understanding of GRAS2 functions, in fruit development of tomato, and demonstrate a strong association between the GRAS gene family and fruit development.

Integrative genomics approaches validate PpYUC11-like as candidate gene for the stony hard trait in peach (P. persica L. Batsch)

BACKGROUND

Texture is one of the most important fruit quality attributes. In peach, stony hard (SH) is a recessive monogenic trait (hd/hd) that confers exceptionally prolonged firm flesh to fully ripe fruit. Previous studies have shown that the SH mutation affects the fruit ability to synthesize appropriate amounts of indol-3-acetic acid (IAA), which orchestrates the ripening processes through the activation of system 2 ethylene pathway. Allelic variation in a TC microsatellite located within the first intron of PpYUC11-like (a YUCCA-like auxin-biosynthesis gene) has been recently proposed as the causal mutation of the SH phenotype.

RESULTS

The simple genetic determinism of the SH trait has been clarified through genome-wide association and LD analyses in a diverse set of accessions, restricting the hd locus to an interval of about 1.8 Mbp in chromosome 6. The comparison of fruit transcriptome data from non-SH (melting flesh) and SH accessions provided an expression patterns overview of the annotated transcripts within the hd locus, confirming the absence of PpYUC11-like expression in SH fruits. To explore further possible associations between genomic variants at the hd locus and the SH phenotype, re-sequencing data of the SH accession 'D41-62' were compared with several SH and non-SH accessions with different genetic backgrounds. A further step of validation was provided through the evaluation of variant-trait association in two bi-parental F₂ populations issued from the SH accession 'D41-62' and a panel of advanced breeding selections, showing perfect co-segregation of the PpYUC11-like intron TC₂₀ allele and the SH phenotype.

CONCLUSIONS

In this study, we provide a multi-level validation of the genetic control of the SH trait through the integration of genome-wide association mapping, transcriptome analysis and whole-genome resequencing data for SH and non-SH accessions, and marker-trait association in a panel of advanced breeding selections and segregating progenies. Collectively, our data confirm with high confidence the role of allelic variation at PpYUC11-like locus as the genetic determinant of the SH trait, opening interesting perspectives at both biological and applied research level.

Gonçalves LS. Genetic variability in Brazilian Capsicum baccatum germplasm collection assessed by morphological fruit traits and AFLP markers

Capsicum baccatum is one of the main pepper species grown and consumed in South America. In Brazil, it is commonly cultivated by family farmers, using mostly the genotypes bishop's hat genotypes (locally cambuci) and red chili pepper (dedo-de-moça). This study had the objective of characterizing 116 C. baccatum accessions from different regions of Brazil, based on morphological fruit descriptors and AFLP (Amplified Fragment Length Polymorphisms) markers. Broad phenotypic variability among the C. baccatum accessions was detected when using morphological fruit descriptors. The Ward modified location model (Ward-MLM) discriminated five groups, based mainly on fruit shape. Six combinations of AFLP primers detected polymorphism in 97.93% of the 2466 identified bands, indicating the high genetic variability in the accessions. The UPGMA coincided with the Bayesian clustering analysis and three large groups were formed, separating the wild variety C. baccatum var. praetermissum from the other accessions. There was no relation between genetic distance and geographical origin of the accessions, probably due to the intense exchange of fruits and seeds between farmers. Morphological descriptors used together with AFLP markers proved efficient in detecting the levels of genetic variability among the accessions maintained in the germplasm collections. These results can be used as an additional source of helpful information to be exploited in C. baccatum breeding programs.

Understanding biological and ecological factors affecting seed germination of the multipurpose tree Anogeissus leiocarpa

Anogeissus leiocarpa (DC.) Guill. & Perr. (Combretaceae) has important economic and cultural value in West Africa as source of wood, dye and medicine. Although this tree is in high demand by local communities, its planting remains limited due to its very low propagation via seed. In this study, X-rays were used to select filled fruits in order to characterise their morphology and seed germination responses to treatment with sulphuric acid and different incubation temperatures. Morphological observations highlighted a straight orthotropous seed structure. The increase in mass detected for both intact and scarified fruits through imbibition tests, as well as morphological observations of fruits soaked in methylene blue solution, confirmed that they are water-permeable, although acid-scarified fruits reached significantly higher mass increment values than intact ones. Acid scarification (10 min soaking in 98% H₂ SO₄ ) positively affected seed germination rate but not final germination proportions. When intact fruits where incubated at a range of temperatures, no seeds germinated at 10 °C, while maximum seed germination (ca. 80%) was reached at 20 °C. T₅₀ values ranged from a minimum of ca. 12 days at 25 °C to a maximum of ca. 34 days at 15 and 35 °C. A theoretical base temperature for germination (T_b ) of ca. 10 °C and a thermal requirement for 50% germination (S) of ca. 195 °Cd were also identified for intact fruits. The results of this study revealed the seed germination characteristics driven by fruit and seed morphology of this species, which will help in its wider propagation in plantations.

Fossil moonseeds from the Paleogene of West Gondwana (Patagonia, Argentina)

PREMISE OF THE STUDY

The fossil record is critical for testing biogeographic hypotheses. Menispermaceae (moonseeds) are a widespread family with a rich fossil record and alternative hypotheses related to their origin and diversification. The family is well-represented in Cenozoic deposits of the northern hemisphere, but the record in the southern hemisphere is sparse. Filling in the southern record of moonseeds will improve our ability to evaluate alternative biogeographic hypotheses.

METHODS

Fossils were collected from the Salamanca (early Paleocene, Danian) and the Huitrera (early Eocene, Ypresian) formations in Chubut Province, Argentina. We photographed them using light microscopy, epifluorescence, and scanning electron microscopy and compared the fossils with similar extant and fossil Menispermaceae using herbarium specimens and published literature.

KEY RESULTS

We describe fossil leaves and endocarps attributed to Menispermaceae from Argentinean Patagonia. The leaves are identified to the family, and the endocarps are further identified to the tribe Cissampelideae. The Salamancan endocarp is assigned to the extant genus Stephania. These fossils significantly expand the known range of Menispermaceae in South America, and they include the oldest (ca. 64 Ma) unequivocal evidence of the family worldwide.

CONCLUSIONS

Our findings highlight the importance of West Gondwana in the evolution of Menispermaceae during the Paleogene. Currently, the fossil record does not discern between a Laurasian or Gondwanan origin; however, it does demonstrate that Menispermaceae grew well outside the tropics by the early Paleocene. The endocarps' affinity with Cissampelideae suggests that diversification of the family was well underway by the earliest Paleocene.

Coupling individual kernel-filling processes with source-sink interactions into GREENLAB-Maize

BACKGROUND AND AIMS

Failure to account for the variation of kernel growth in a cereal crop simulation model may cause serious deviations in the estimates of crop yield. The goal of this research was to revise the GREENLAB-Maize model to incorporate source- and sink-limited allocation approaches to simulate the dry matter accumulation of individual kernels of an ear (GREENLAB-Maize-Kernel).

METHODS

The model used potential individual kernel growth rates to characterize the individual potential sink demand. The remobilization of non-structural carbohydrates from reserve organs to kernels was also incorporated. Two years of field experiments were conducted to determine the model parameter values and to evaluate the model using two maize hybrids with different plant densities and pollination treatments. Detailed observations were made on the dimensions and dry weights of individual kernels and other above-ground plant organs throughout the seasons.

KEY RESULTS

Three basic traits characterizing an individual kernel were compared on simulated and measured individual kernels: (1) final kernel size; (2) kernel growth rate; and (3) duration of kernel filling. Simulations of individual kernel growth closely corresponded to experimental data. The model was able to reproduce the observed dry weight of plant organs well. Then, the source-sink dynamics and the remobilization of carbohydrates for kernel growth were quantified to show that remobilization processes accompanied source-sink dynamics during the kernel-filling process.

CONCLUSIONS

We conclude that the model may be used to explore options for optimizing plant kernel yield by matching maize management to the environment, taking into account responses at the level of individual kernels.

Image-based dynamic quantification and high-accuracy 3D evaluation of canopy structure of plant populations

BACKGROUND AND AIMS

Global agriculture is facing the challenge of a phenotyping bottleneck due to large-scale screening/breeding experiments with improved breeds. Phenotypic analysis with high-throughput, high-accuracy and low-cost technologies has therefore become urgent. Recent advances in image-based 3D reconstruction offer the opportunity of high-throughput phenotyping. The main aim of this study was to quantify and evaluate the canopy structure of plant populations in two and three dimensions based on the multi-view stereo (MVS) approach, and to monitor plant growth and development from seedling stage to fruiting stage.

METHODS

Multi-view images of flat-leaf cucumber, small-leaf pepper and curly-leaf eggplant were obtained by moving a camera around the plant canopy. Three-dimensional point clouds were reconstructed from images based on the MVS approach and were then converted into surfaces with triangular facets. Phenotypic parameters, including leaf length, leaf width, leaf area, plant height and maximum canopy width, were calculated from reconstructed surfaces. Accurate evaluation in 2D and 3D for individual leaves was performed by comparing reconstructed phenotypic parameters with referenced values and by calculating the Hausdorff distance, i.e. the mean distance between two surfaces.

KEY RESULTS

Our analysis demonstrates that there were good agreements in leaf parameters between referenced and estimated values. A high level of overlap was also found between surfaces of image-based reconstructions and laser scanning. Accuracy of 3D reconstruction of curly-leaf plants was relatively lower than that of flat-leaf plants. Plant height of three plants and maximum canopy width of cucumber and pepper showed an increasing trend during the 70 d after transplanting. Maximum canopy width of eggplants reached its peak at the 40th day after transplanting. The larger leaf phenotypic parameters of cucumber were mostly found at the middle-upper leaf position.

CONCLUSIONS

High-accuracy 3D evaluation of reconstruction quality indicated that dynamic capture of the 3D canopy based on the MVS approach can be potentially used in 3D phenotyping for applications in breeding and field management.

Quantifying within-plant spatial heterogeneity in carbohydrate availability in cotton using a local-pool model

Background and Aims

Within-plant spatial heterogeneity in the production of and demand for assimilates may have major implications for the formation of fruits. Spatial heterogeneity is related to organ age, but also to position on the plant. This study quantifies the variation in local carbohydrate availability for the phytomers in the same cohort using a cotton growth model that captures carbohydrate production in phytomers and carbohydrate movement between phytomers.

Methods

Based on field observations, we developed a functional-structural plant model of cotton that simulates production and storage of carbohydrates in individual phytomers and transport of surplus to other phytomers. Simulated total leaf area, total above-ground dry mass, dry mass distribution along the stem, and dry mass allocation fractions to each organ at the plant level were compared with field observations for plants grown at different densities. The distribution of local carbohydrate availability throughout the plant was characterized and a sensitivity analysis was conducted regarding the value of the carbohydrate transport coefficient.

Key Results

The model reproduced cotton leaf expansion and dry mass allocation across plant densities adequately. Individual leaf area was underestimated at very high plant densities. Best correspondence with measured plant traits was obtained for a value of the transport coefficient of 0.1 d-1. The simulated translocation of carbohydrates agreed well with results from C-labelling studies. Moreover, simulation results revealed the heterogeneous pattern of local carbohydrate availability over the plant as an emergent model property.

Conclusions

This modelling study shows how heterogeneity in local carbohydrate production within the plant structure in combination with limitations in transport result in heterogeneous satisfaction of demand over the plant. This model provides a tool to explore phenomena in cotton that are thought to be determined by local carbohydrate availability, such as branching pattern and fruit abortion in relation to climate and crop management.

When the BRANCHED network bears fruit: how carpic dominance causes fruit dimorphism in Aethionema

Life in unpredictably changing habitats is a great challenge, especially for sessile organisms like plants. Fruit and seed heteromorphism is one way to cope with such variable environmental conditions. It denotes the production of distinct types of fruits and seeds that often mediate distinct life-history strategies in terms of dispersal, germination and seedling establishment. But although the phenomenon can be found in numerous species and apparently evolved several times independently, its developmental time course or molecular regulation remains largely unknown. Here, we studied fruit development in Aethionema arabicum, a dimorphic member of the Brassicaceae family. We characterized fruit morph differentiation by comparatively analyzing discriminating characters like fruit growth, seed abortion and dehiscence zone development. Our data demonstrate that fruit morph determination is a 'last-minute' decision happening in flowers after anthesis directly before the first morphotypical differences start to occur. Several growth experiments in combination with hormone and gene expression analyses further indicate that an accumulation balance of the plant hormones auxin and cytokinin in open flowers together with the transcript abundance of the Ae. arabicum ortholog of BRANCHED1, encoding a transcription factor known for its conserved function as a branching repressor, may guide fruit morph determination. Thus, we hypothesize that the plasticity of the fruit morph ratio in Ae. arabicum may have evolved through the modification of a preexisting network known to govern correlative dominance between shoot organs.

Physiological characterization of leaf and internode after bud break in Japanese indigenous Koshu grape by comparative RNA sequencing analysis

Koshu is indigenous to Japan and considered the most important wine grape in Japan. Koshu grape berry possesses characteristics that make it unique from European V. vinifera as wine grape. However, the physiological characteristics of Koshu leaf and internode remain unknown. An understanding of those characteristics would contribute to improvements in Koshu cultivation, thereby enhancing grape berry and wine quality. To identify the genes responsible for the physiological characteristics of Koshu, we comprehensively analyzed leaf and internode differences at the transcriptome level between Koshu and Pinot Noir by RNA sequencing. A total of 248 and 131 differentially expressed genes (DEGs) were detected in leaves and internodes, respectively. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses of these DEGs revealed that "flavonoid biosynthesis" and "glutathione metabolism" pathways were significantly enriched in Koshu leaves. On the other hand, when internodes were compared, "flavonoid"-related GO terms were specifically detected in Koshu. KEGG pathway enrichment analysis suggested that the expression of such genes as leucoanthocyanidin reductase and flavonol synthase in the flavonoid biosynthesis pathway was higher in Koshu than Pinot Noir. Measurement of the relative expression levels of these genes by RT-qPCR validated the results obtained by RNA sequencing. The characteristics of Koshu leaf and internode, which are expected to produce flavonoids with antibacterial activity and UV protection function, would suit Japanese climate as a survival strategy.

A role for fruit structure in seed survival and germination of Swartzia langsdorffii Raddi beyond dispersal

Diaspore structure has been hypothesised to play a role in seed viability and/or germination of recalcitrant seeds, especially for Swartzia langsdorffii. Thus, this work aims to (i) investigate the in situ contribution of pericarp and aril on seed viability and germination, and (ii) identify morphoanatomical traits of S. langsdorffii diaspores that allow its desiccation-sensitive seeds to remain viable. The role of the pericarp and aril in seed survival and germination was investigated by placing the whole fruit, whole seeds (arillate seed) and bare seeds (without aril) in soil in the forest understorey, assessing germination, emergence, dead, firm and predated seeds, and water content of pericarps, arils and seeds. Correlation analysis was performed between environmental variables and physiological parameters. Histochemical features of diaspores were also investigated. Pericarp water content fell after several months, while the aril maintained its water content. Seeds did not lose water even without the presence of the pericarp and aril. However, presence of the pericarp promoted seed water content, viability and germination long after dispersal. The embryo had a thickened outer periclinal cell wall. Pericarp and aril are not essential to prevent water loss in seeds, but do help to retain seed moisture, favouring viability maintenance and promoting germination during the rainy season. Morphoanatomical features of seeds are suggested as main factors that reduce water loss. Survival of these desiccation-sensitive seeds upon dispersal during the dry season appears to be facilitated by multiple diaspore features that prevent viability loss.

Reproductive biology of Aechmea bracteata (Sw.) Griseb. (Bromelioideae: Bromeliaceae)

Individuals of Aechmea bracteata show inflorescences with red scape bracts and odourless, yellow, tubular diurnal flowers, with closely arranged sexual organs, producing a large amount of fruits. In order to investigate the reproductive system of this species, a suite of characters was assessed: phenology, floral morphology and biology, nectar production dynamics, and fruit and seed production and germination, as a result of controlled pollination crosses. The study was conducted during two flowering seasons in wild populations in Yucatán, Mexico. Results suggest an annual flowering pattern with one flowering peak; flowers were diurnal, showing partial dichogamy (protandry)-herkogamy, anthers and stigma become mature before floral aperture, which could lead to self-pollination, nectar is produced during anthesis, varying in volume and total sugar concentration during the day; fruits and seeds were produced in all experimental crosses (cross-pollination, obligated cross-pollination, assisted and unassisted selfing, geitonogamy and apomixis), as well as high percentage seed germination. Several species of Aechmea are reportedly self-compatible and autogamous, as suggested by results of selfing and non-assisted selfing crosses, but these results are negated by the presence of apomixis, indicating that the species is apomictic. This is the first report of this breeding system for subgenus Aechmea and the sixth for Bromeliaceae. Polyembryony is here suggested for the first time in this genus and family based on the fact that more seeds were recorded that expected based on ovule numbers. Finally, when performing experimental crosses, estimating reproductive success based on number of seeds is a better approach than number of fruits, due to the effect of pseudogamy.

Independent recruitment of a novel seed dispersal system by camel crickets in achlorophyllous plants

The seeds of most heterotrophic plants, commonly referred to as dust seeds, are typically dispersed in the air like dust particles. Therefore, little attention has been paid to how seeds of heterotrophic plants are dispersed, owing to the notion that wind dispersal is the dominant strategy. However, inconspicuous but fleshy, indehiscent fruit can be observed in distantly related plants that have independently evolved full heterotrophy. Here I investigated the seed dispersal system in three unrelated fully heterotrophic plants with fleshy, indehiscent fruits (Yoania amagiensis, Monotropastrum humile and Phacellanthus tubiflorus) by direct observation, a differential exclusion experiment of fruit feeders and investigation on seed viability through the digestive tract. The present study revealed that camel crickets are the major seed disperser in three achlorophyllous plants in the study population. This represents the first evidence of seed dispersal by camel crickets in any angiosperm species. These heterotrophic plants grow in the understorey of densely vegetated forests where wind is probably an ineffective seed dispersal agent. Life-history traits of the achlorophyllous plants associated with heterotrophic lifestyles, such as colonization of dark understorey habitats and dust seeds, could facilitate independent recruitment of the novel endozoochorous seed dispersal system by camel crickets.

Changes in Membrane Lipid Composition and Function Accompanying Chilling Injury in Bell Peppers

Bell peppers are vulnerable to low temperature (<7°C) and subject to chilling injury (CI). To elucidate the relationship between cell membrane lipid composition and CI, a membrane lipidomic approach was taken. In addition, we performed microstructural analysis and low-field nuclear magnetic resonance to better understand CI. We also monitored primary physiological metabolism parameters to explain lipidomics. Our study indicated that cellular structure damage was more serious at 4°C, mostly represented by damage to the plasmalemma and plastid degradation. Membrane lipidomic data analysis reveals monogalactosyldiacylglycerol, phosphatidylcholine, phosphatidylethanolamine and phosphatidic acid as crucial biomarkers during CI. Furthermore, the significant increase in proline, electrolyte leakage and phospholipase D in chilled fruits also proved that membrane lipid metabolism is involved in the response to low temperature stress. To our knowledge, this study is the first attempt to describe the CI mechanisms in bell peppers based on membrane lipidomics.

Inferring long-distance dispersal modes in American amphitropically disjunct species through adaptive dispersal structures

PREMISE OF THE STUDY

A repeated pattern of American amphitropical disjunct species or sister species distributed on either side of the equator has long-fascinated botanists, but the modes of these disjunctions remain untested. We evaluated diaspore morphology to generate hypotheses on probable dispersal mechanisms.

METHODS

The sizes and structures of diaspores, habit, habitat, distribution, and dispersal units were collected for 108 species from literature searches and herbarium specimens. Variation was evaluated with summary statistics, χ² tests with Monte Carlo simulations, ANOVAs, and the nonparametric Mann-Whitney test.

KEY RESULTS

Seeds were the dispersing diaspore in 38.0% of the species, 45.4 were dispersed as fruits, and the remaining were dispersed as infructescences or spores. Diaspores were epizoochorous (52.8%), anemochorous (20.4%), achorous (15.7%), endozoochorous (8.3%), and hydrochorous (2.8%). Epizoochory was significantly greater than expected. Zoochory occurred more frequently than expected when considering achorous diaspores as animal-dispersed. Most species were associated with wetland, woodland, and grassland habitats. An ANOVA revealed that diaspores associated with hydrochory were larger and anemochory was smaller; all other syndromes were not significantly different.

CONCLUSIONS

Botanists have long-held the assumption that bird migrations are responsible for amphitropical disjunctions. Our results support this hypothesis, with the majority of these events occurring by external attachment of small fruits. However, our results also indicate that anemochory might play a greater role in producing amphitropical distributions than previously thought and at a greater rate than endozoochory or hydrochory.