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The induction and regeneration of protocorm-like bodies (PLBs) is a morphogenetic pathway widely used for orchid micropropagation. As endopolyploidy, i.e., the coexistence of cells with different ploidy levels, is a common feature in orchid tissues, a natural question arises when using somatic tissues as explants for orchid micropropagation: does endopolyploidy in explants affect the cytogenetic stability of regenerated plantlets? To answer this question, Epidendrum fulgens was used as a model plant, and flow cytometry was used to analyze endopolyploidy in pollinia, petals, labella, leaf bases, leaf tips, root tips, and protocorm bases and apices, which were subsequently used as explants for PLB induction and plant regeneration. Ploidy screenings showed contrasting ploidy patterns in samples, endopolyploidy being detected in all tissues, with C-values ranging from 1 to 16C. Protocorm bases and root tips presented the highest proportion of endopolyploidy, while petals and protocorm apices showed the lowest proportion. Flower parts exhibited high oxidation for PLB induction and pollinia failed to produce PLB or callus. The highest induction rate occurred at 10 µM TDZ, with 92%, 22%, and 0.92% for protocorm bases, leaves, and root tips, respectively. Plantlets were more easily regenerated from PLBs induced from protocorm bases than from leaves and roots. Doubled ploidy levels were registered in a proportion of 11% and 33% for PLB-regenerated plantlets obtained from protocorm bases and leaf bases, respectively, which was not directly associated with the proportion of endopolyploid cells or cycle value of explants.Key messageExplants have different endopolyploid patterns and cycle values. Polyploid regenerants were obtained from leaves and protocorms, although in rates not associated with the proportion of endopolyploid cells in the explants.

Corunastylis species produce some of the smallest, fly-pollinated flowers of Australian orchids to offer liquid rewards. We observed and collected pollinarium vectors of four Corunastylis species ( C. filiformis, C. fimbriata, C. rufa and C. ruppii ) with overlapping flowering periods during the summer–autumn months at five sites in New South Wales (NSW), Australia. The most common pollinarium vectors of all species were females of a single morphotype in the genus Conioscinella (Diptera: Chloropidae). This morphotype was less than 3 mm in length and carried dorsal depositions of pollinaria on its thorax. A chloropid could carry as many as two pollinaria and 25–50% of attached pollinia showed erosion, suggesting previous contact with receptive stigmas. Bagging experiments on three species showed low rates of mechanical self-pollination and no fruit set in C. filiformis , C. fimbriata and C. ruppii . The conversion rate of insect-pollinated flowers into fruit varied from 35 to 91% among these three species in NSW versus C. ciliata in Victoria. Seed development also varied with > 42–70% of seeds in the three species in NSW containing fully developed embryos. High levels of reproductive success in these three species in NSW and C. ciliata in Victoria were the same as for fruit sets in other orchid species in other genera with nectar-secreting flowers. As flowering periods, distributions and primary pollinators of four Corunastylis species in NSW overlapped so broadly there appears to be a lack of pre-zygotic interspecific isolation mechanisms. This study provided important pollination and reproductive information towards future conservation management of these orchid species.

Based on evidence found in a specimen collected by J. A. Steyermark in the vicinity of Mount Roraima in 1944, such as the described colors of the flowers and shape of the labellum, and the shape and size of the antennae, the pollinarium, and the pollinia, a new natural hybrid between Catasetum discolor and C. planiceps is described and illustrated as C. ×steyermarkii. Both putative parents have been collected in the same area. An annotated list of all the species of Catasetum hitherto reported in the vicinity of Mount Roraima is presented in Appendix I, and new nothospecies (pro sp.) and a nomenclatural notes in Appendix II.

We studied the variation in the pollinarium and pistil of Epidendroideae and reconstructed the ancestral states of the characters (pollinia number, pollinium orientation, pollinium with suture, and pollinium texture). The pollinarium is complete (formed by pollinium, caudicle, stipe, and viscidium) in Vandeae, Epidendreae, and Cymbidieae, but the caudicle is absent in some Aeridinae and the viscidium in Laeliinae and Pleurothallidinae. Neottieae, Arethuseae, Sobralieae, Epidendreae, and Xerorchideae included some genera having sessile pollinia. The more frequent state in the family is to have two pollinia, followed by four, eight, and six pollinia. The pistil is unilocular, although it seems to have experienced reversals several times within Epidendroideae because intermediate states were observed (e.g. Vanda and Angraecum). In these cases, a prolongation of the placental tissue is developed that in Huntleya and Peristeria make contact but do not fuse. Most members of the subfamily have pistil composed of three carpels divided into six emerging valves, but only three are fertile. In Cattleya and Sophronitis the sterile valves are much reduced and the pistil seems to have only three valves. We have generated useful and valuable information to understand the evolution of the reproductive organs in Epidendroideae. Probably, these transformations in the pollinarium and pistil have co-evolved in tandem with pollinators to make the pollination more efficient. Our results suggest that the common ancestor of Epidendroideae had a complete pollinarium, formed probably of four juxtaposed granular pollinia without suture, bearing caudicle, tegular stipe and viscidium, but several early transformations occurred during the Epidendroideae diversification.

Summary The Orchidaceae is a diverse and ecologically important plant family. Approximately 69% of all orchid species are epiphytes, which provide diverse microhabitats for many small animals and fungi in the canopy of tropical rainforests. Moreover, many orchids are of economic importance as food flavourings or ornamental plants. Phalaenopsis aphrodite, an epiphytic orchid, is a major breeding parent of many commercial orchid hybrids. We provide a high‐quality chromosome‐scale assembly of the P. aphrodite genome. The total length of all scaffolds is 1025.1 Mb, with N50 scaffold size of 19.7 Mb. A total of 28 902 protein‐coding genes were identified. We constructed an orchid genetic linkage map, and then anchored and ordered the genomic scaffolds along the linkage groups. We also established a high‐resolution pachytene karyotype of P. aphrodite and completed the assignment of linkage groups to the 19 chromosomes using fluorescence in situ hybridization. We identified an expansion in the epiphytic orchid lineage of FRS5‐like subclade associated with adaptations to the life in the canopy. Phylogenetic analysis further provides new insights into the orchid lineage‐specific duplications of MADS‐box genes, which might have contributed to the variation in labellum and pollinium morphology and its accessory structure. To our knowledge, this is the first orchid genome to be integrated with a SNP‐based genetic linkage map and validated by physical mapping. The genome and genetic map not only offer unprecedented resources for increasing breeding efficiency in horticultural orchids but also provide an important foundation for future studies in adaptation genomics of epiphytes.

Despite the wide inflorescence diversity among angiosperms, the effects of inflorescence architecture (three-dimensional flower arrangement) on pollinator behaviour and mating success have not been sufficiently studied in natural plant populations. Here, we investigated how inflorescence architecture affected inter- and intra-plant pollinator movements and consequent mating success in a field population of Spiranthes sinensis var. amoena (S. sinensis). In this species, the flowers are helically arranged around the stem, and the degree of twisting varies greatly among individuals. The large variation in inflorescence architecture in S. sinensis results from variation in a single structural parameter, the helical angle (the angular distance between neighbour-flower directions). The numbers of visits per inflorescence and successive probes per visit by leaf-cutting bees decreased with helical angle, indicating that individual flowers of tightly twisted inflorescences received less visitations. As expected from pollinator behaviour, pollinia removal and fruit set of individual flowers decreased with helical angle. Meanwhile, geitonogamy decreased in tightly twisted inflorescences. Our novel findings demonstrate that natural variation in inflorescence architecture significantly affects pollinator behaviour and reproductive success, suggesting that inflorescence architecture can evolve under pollinator-mediated natural selection in plant populations. We also discuss how diverse inflorescence architectures may have been maintained in S. sinensis populations.

The Orchidaceae is a large family of perennial herbs especially noted for the exceptional diversity of specialized flowers. Elucidating the genetic regulation of flowering and seed development of orchids is an important research goal with potential utility in orchid breeding programs. Auxin Response Factor (ARF) genes encode auxin-responsive transcription factors, which are involved in the regulation of diverse morphogenetic processes, including flowering and seed development. However, limited information on the ARF gene family in the Orchidaceae is available. In this study, 112 ARF genes were identified in the genomes of 5 orchid species (Apostasia shenzhenica, Dendrobium catenatum, Phalaenopsis aphrodite, Phalaenopsis equestris and Vanilla planifolia,). These genes were grouped into 7 subfamilies based on their phylogenetic relationships. Compared with the ARF family in model plants, such as Arabidopsis thaliana and Oryza sativa, one group of ARF genes involved in pollen wall synthesis has been lost during evolution of the Orchidaceae. This loss corresponds with absence of the exine in the pollinia. Through mining of the published genomic and transcriptomic data for the 5 orchid species: the ARF genes of subfamily 4 may play an important role in flower formation and plant growth, whereas those of subfamily 3 are potentially involved in pollen wall development. the study results provide novel insights into the genetic regulation of unique morphogenetic phenomena of orchids, which lay a foundation for further analysis of the regulatory mechanisms and functions of sexual reproduction-related genes in orchids.Key messageGenome wide analysis and expression pattern analysis of ARF genes in five 20 Orchidaceae species highlight their Evolutionary characteristics and roles in IAA response.

Among the factors thought to have favoured the evolution of deception (rewardlessness) in orchids is the reduction of pollinator-mediated selfing when unrewarded pollinators visit fewer flowers per inflorescence. We obtained data on natural levels of geitonogamy in the deceptive orchids Dactylorhiza sambucina and Himantoglossum hircinum by monitoring the dispersal and receipt of colour-coded pollinia. As donors, we marked 185 flowers of D. sambucina and 956 flowers of H. hircinum. In D. sambucina, 30% of the pollinator-visited flowers and 62% of the marked inflorescences experienced geitonogamous pollination events. In H. hircinum, the respective percentages were 36 and 71%. The furthest pollen transport distance in the Andrena-pollinated H. hircinum was 6.9 m (median 1.27 m), while the furthest transport in the bumblebee-pollinated D. sambucina was 176 m (median 1.23 m), a record in Orchidaceae. An analysis of pollen-tracking studies in orchids revealed geitonogamy levels of around 40% (based on individuals; 19-37% based on flowers) in both rewardless species and rewarding ones. This is similar to geitonogamy levels in other animal-pollinated angiosperms, although the data basis for comparison may still be too small. So far, however, it is not evident that rewardless orchids experience particularly low levels of geitonogamy.

The orchid Dactylorhiza sambucina shows a stable and dramatic flower-color polymorphism, with both yellow- and purple-flowered individuals present in natural populations throughout the range of the species in Europe. The evolutionary significance of flower-color polymorphisms found in many rewardless orchid species has been discussed at length, but the mechanisms responsible for their maintenance remain unclear. Laboratory experiments have suggested that behavioral responses by pollinators to lack of reward availability might result in a reproductive advantage for rare-color morphs. Consequently, we performed an experiment varying the relative frequency of the two color morphs of D. sambucina to test whether rare morph advantage acted in the natural habitat of the species. We show here clear evidence from this manipulative experiment that rare-color morphs have reproductive advantage through male and female components. This is the first demonstration, to our knowledge, that negative frequency-dependent selection through pollinator preference for rare morphs can cause the maintenance of a flower-color polymorphism.

This study aimed to examine the pollen and pollinia morpho-structure of 18 horticultural Apocynaceous species. Advanced light and scanning electron microscopy (LM and SEM) were used to elaborate on and examine the systematic importance of pollen and pollinia micromorphology. Pollen grains were first acetolysed, which was followed by visualisation of their sculpturing features. The quantified data were subjected to statistical tools to elucidate dendrogram clustering and principal component analysis to reveal pollen/pollinia morphotypes. The size of pollen is variable, ranging from 113.45 μm in to 23.4 μm in The study revealed tetrad, tetraporate, and tricolporate grains. Sculpturing (exine ornamentation) varies from reticulate perforate to reticulate. Pollinum shape was observed to be narrow oblong, obovate, orbicular, and reniform. Reticulate-psilate sculptural features were prominent among pollinia surfaces. Based on examination, it was ascertained that the minimum exine thickness in was 4.9 μm, whereas the corresponding number in was 1.35 μm. Taxonomic identification keys were constructed separately based on pollen/pollinia characters to identify the Apocynaceous taxa. In the presented study, seven pollen shapes were observed: from oblate to per prolate. The findings confirm that morphopollinic traits differ amongst genera of Apocynaceous species. However, these features can be used to distinguish the Apocynaceous taxa. The results show that structural characteristics of pollen and pollinia can help accurately identify Apocynaceous species.