Epiphytic Orchid Research Articles

Orchid diversity in antropogenic-induced degraded tropical rainforest, an extrapolation towards conservation

The uncontrolled logging in Peninsular Malaysia and the resulting mudslides in the lowland areas have been perilous, not to just humans, but also to another biodiversity, including the wild orchids. Their survival in these highly depleted areas is being overlooked due to the inaccessible and harsh environment. This paper reports on the rescue of orchids at risk from the disturbed forests for ex-situ conservation, the identification of the diversity of orchids and the evaluation of the influence of micro-climatic changes induced by clear-cut logging towards the resilience of orchids in the flood-disturbed secondary forests and logged forests in Terengganu and Kelantan, located at the central region of Peninsular Malaysia, where the forest destruction by logging activities has been extensive. 109 orchid species belonging to 40 genera were collected from the disturbed areas. The diversity and data analyses show that the disturbed secondary forests had a higher orchid density (0.0133 plants/m2) than the logged sites (0.0040 plants/m2) as the habitat conditions were more dependable. Nevertheless, the logged forests harboured a higher diversity of orchids (H=4.50 and D=0.99) of which 97.9% were epiphytes. Eleven rare species were found along with six species endemic to Peninsular Malaysia, with two species new to science. The results highlighted the factors that allow the orchids to flourish or suffer in the disturbed forests. The logged forests had a higher ambient temperature and lower moisture level than the mud flood-disturbed and canopy-covered secondary forests. Apart from the extensive ground vegetation due to logs dragging extraction, low soil moisture and absence of leaf litter were believed to be the major attributes causing the low abundance of terrestrial orchids. The high abundance and diversity of epiphytic orchids and the large difference of their densities between the logged sites were influenced by the densities of fallen trees hosting orchid(s), disturbance-induced dryness stresses, durations of exposure to the anthropogenic-induced disturbance, and less favourable soil conditions for the terrestrial orchids.
 
 Key words: conservation, diversity, dryness stress, ecology, epiphyte, logged forest, mudslides, Orchidaceae

Chemical composition of cell walls in velamentous roots of epiphytic Orchidaceae.

The chemical composition of the cell walls strongly affects water permeability and storage in root tissues. Since epiphytic orchids live in a habitat with a highly fluctuating water supply, the root cell walls are functionally important. In the present study, we used histochemistry and immunocytochemistry techniques in order to determine the composition of the cell walls of root tissues of 18 epiphytic species belonging to seven subtribes across the Orchidaceae. The impregnation of lignin in the velamen cells reinforces its function as mechanical support and can facilitate apoplastic flow. Pectins, as well cellulose and lignins, are also essential for the stability and mechanical support of velamen cells. The exodermis and endodermis possess a suberinized lamella and often lignified walls that function as selective barriers to apoplastic flow. Various cortical parenchyma secondary wall thickenings, including phi, reticulated, and uniform, prevent the cortex from collapsing during periods of desiccation. The presence of highly methyl-esterified pectins in the cortical parenchyma facilitates the formation of gels, causing wall loosening and increased porosity, which contributes to water storage and solute transport between cells. Finally, cells with lipid or lignin impregnation in the cortical parenchyma could increase the water flow towards the stele.

Characteristics of Wild Orchids in Mallawa Resort at Bantimurung Bulusaraung National Park, South Sulawesi, Indonesia

This study aims to determine the characteristics of wild orchids in the area of Resort Mallawa, Bantimurung Bulusaraung National Park. This type of research is descriptive with the exploration method, which is tracking the study area which is known to have a fairly high distribution of wild orchids. Exploration of wild orchids is carried out at 85 distribution points, with an altitude of 432 meters above sea level to 849 m above sea level. The results showed that there were 40 types of orchids, 33 species identified, and 7 species not identified. Based on the growth properties of wild orchids found were dominated by 35 species of epiphytic orchids, while for the type of growth was dominated by 24 species of sympodial orchids. The most found locations of wild orchids are in Mallenreng Hamlet I. The most common species is Trichoglottis geminata. Based on the height of the place, the species that grows at the highest position is Coelogyne sp., while in the lowest position is Dendrobium sp. 1. Based on the visual intensity of light, orchids were found in the shade as many as 5 species, half sheltered as many as 21 species, while in the open as many as 4 species. There are 5 orchid species that can grow in the shade and half shade, 3 species that grow in half shade and open places, and 2 species that can grow in three places. By knowing the presence and diversity of wild orchids in the study area shows that the ecosystem in the area is still quite good, considering that wild orchids are plants that are quite susceptible to interference.

The complete chloroplast genome of Dendrobium longicornu (Orchidaceae)

Dendrobium longicornu Lindl is an epiphytic orchid with significant ornamental values. Here, we report the first complete chloroplast genome of D. longicornu. The complete chloroplast (cp) genome sequence of D. longicornu is 160,024 bp in length and consisted of two inverted repeats (IRs, 25,403 bp), which were separated by a large single copy region (LSC, 88,075 bp) and a small single copy region (SSC, 21,143 bp). The cp genome encoded 142 genes, of which 110 were unique genes (80 protein-coding genes, 26 tRNAs and 4 rRNAs). Phylogenetic analysis showed that D. longicornu clustered together with D. ellipsophy.

Next-generation sequencing yields the complete chloroplast genome of Pleione chunii, a vulnerable orchid in China

Pleione chunii is a vulnerable epiphytic orchid with significant ornamental value. Here, we report the first complete chloroplast genome of P. chunii. The circular genome was 158,880 bp in length and consisted of a pair of inverted repeats (IR 26,465 bp), which were separated by a large single copy region (LSC 87,259 bp) and a small single copy region (SSC 18,691 bp). It contained 115 unique genes, including 87 protein-coding genes, 38 tRNAs, and eight rRNAs. The maximum-likelihood phylogenetic analysis indicated that P. chunii was sister to P. bulbocodioides and P. formosana.

The complete chloroplast genome of Eria corneri (Orchidaceae)

Eria corneri is a perennial epiphytic orchid distributed in southeastern China with high value of ornamental and medicinal. In this study, the complete chloroplast genome sequence of E. corneri was determined from Illumina pair-end sequencing data. The complete chloroplast genome sequence of E. corneri is 150,538 base pairs (bp) in length, including one large single-copy region (LSC, 85,941 bp), one small single-copy region (SSC, 13,099 bp), and a pair of inverted repeat regions (IRs) of 25,749 bp. Besides, the complete chloroplast genome contains 132 genes, including 77 protein-coding genes, 38 tRNA genes, and 8 rRNA genes. Phylogenetic analysis showed that E. corneri was most closely related to Calanthe triplicata and Calanthe davidii. Our study provides a foundation for the identification and genotyping of Eria species.

The complete chloroplast genome of Cymbidium floribundum var. pumilum (Orchidaceae)

Cymbidium floribundum var. pumilum is an epiphytic orchid distributed in the southern China. It has a high ornamental value and always be used as a hybrid parent. In this study, we obtained a complete chloroplast genome of C. floribundum var. pumilum from BGISEQ-500 sequencing data. The total chloroplast genome was 155,291 bp in length, consisting of a large single copy region (LSC 84,415 bp), a small single copy region (SSC 17,484 bp), and two inverted repeat regions (IRA and IRB 26,696 bp). The complete chloroplast genome contains 139 genes, including 80 protein-coding genes, 38 transfer RNA (tRNA) genes, and 8 ribosomal RNA (rRNA) genes. In addition, the phylogenetic analysis indicates that C. floribundum var. pumilum was sister to section Geocymbidium, section Pachyrhizanthe and section Jensoa. The chloroplast genome will contribute to establish an effective conservation strategy for C. floribundum var. pumilum.

Antioxidant and α-glucosidase inhibitor activities of Grammatophyllum speciosum Blume

Grammatophyllum speciosum Blume is the largest epiphytic orchid. In Thailand, it is used to prepare a herbal elixir against inflammation. This study determined antioxidant activity and α-glucosidase inhibitor activity in ethanol extracts prepared from leaf, rhizome+root and pseudobulbs of 3 different age plants: 6-year-old plants, 1-year-old plants and in vitro plantlets. For 1-year-old plants and in vitro plantlets, only 2 parts, leaf and rhizome+root, were used. The experimental design was a completely randomized design. The experiments were done in duplicate and measurements were applied in triplicate (n=3). After extraction of fresh and dried samples, antioxidant activity and α-glucosidase inhibitor activity were determined. Extractions from fresh samples of 6-year-old leaf and rhizome+root parts yielded the highest DPPH free radical scavenging activity (77.68 and 76.95%, respectively), but were not different from Trolox, 100 μg mL(‑1), the positive control (83.85%). The IC50 value of the DPPH extract from 6-year-old leaves and rhizomes+roots and Trolox were 32.07, 17.87 and 7.43 µg mL(‑1), respectively. For α-glucosidase inhibitor activity, extractions from 6-year-old rhizome+root (both fresh and dry samples) showed strong activity (84.88 and 85.47%, respectively) and were significantly lower than acarbose, 1 mg mL(‑1), (positive control, 94.50%). The other plant samples had weak activity (8-13%). The IC(50) value of α-glucosidase inhibitor activity in extracts from 6-year-old rhizome+root (fresh sample) and acarbose were 443.52 and 390.42 µg mL(‑1), respectively. Results suggested that 6-year-old rhizome+root of G. speciosum could be a potential source of natural antidiabetic medicine. The 6-year-old leaf and 6-year-old rhizome+root could be sources of antioxidant.

In vitro Seed Germination, Protocorm Formation and Plantlet Regeneration in Aerides ringens Fisher

An attempt was made to in vitro seed germination and plantlet regeneration in Aerides ringens, a threatened, endemic and epiphytic orchid. Five basal media Knudson C (KC), Vacin and Went (VW), Burgeff’s (N3f), half strength MS, MS were examined for their effectiveness. Germination occurred in all the media. However, KC medium proved to be the best for seed germination (70.8%) and half strength MS was superior for the differentiation of protocorm like bodies (PLBs) into seedlings. The seeds were also cultured on various plant growth regulators (PGRs) to evaluate their effectiveness on seed germination and further differentiation. Among the PGRs tested, 0.57 μM IAA (IAA 89.3%), 4.64 μM Kn (88.6%) and 2.21 μM BAP (90.7%) and 0.57 μM IAA + 0.55 μM BAP (96.5%) were stimulated the germination and further differentiation of PLBs into seedlings. The concentrations of 2.21 μM BAP and combination of 0.57 μM IAA + 0.55 μM BAP stimulated the formation of MPLBs, which later differentiated into shoots and roots. Four potting substrates were evaluated for Ex vitro seedling survivability of which brick: charcoal: decaying litter: coconut husk (1 : 1 : 1 : 1) gave maximum survival rate (89.0%).
 Plant Tissue Cult. & Biotech. 29(1): 49-62, 2019 (June)

In vitro Mass Propagation of Cymbidium aloifolium (L.) Sw.

Cymbidium aloifolium (L.) Sw. is an epiphytic orchid distributed locally in Bangladesh. Natural populations of this orchid are under threat due to its high commercial value in the floriculture industry by over exploitation. Mass propagation provides an alternative means of satisfying the demand. In this study, half strength of MS supplemented with BAP or different combinations with NAA was evaluated for seed germination and early protocorm development of C. aloifolium (L.) Sw. The maximum percentage of seed germination (98) was obtained on modified MS (half strength of micro and macro nutrients and full strength of vitamin) supplemented with 0.5 mg/l BAP and 0.5 mg/l NAA after three weeks of culture. Maximum number of shoots (9.6 shoots per single shoot) were developed from shoot tip explants on half strength of MS supplemented with 1.0 mg/l BAP and 0.5 mg/l NAA. The most effective auxin source promoting root production (3.2 roots per shoot) was 1.0 mg/l IBA in combination with 0.5 mg/l BAP. The seedlings were successfully acclimatized (survival percentage 99) in a nethouse using a rooting medium of crushed sterile brick, cocopit and charcoal (1 : 1 : 1 v/v).
 Plant Tissue Cult. & Biotech. 29(1): 73-79, 2019 (June)

Inventory and exploration of orchid in Polewali Mandar, West Sulawesi, Indonesia

Sulawesi is the fourth largest island in Indonesia. Sulawesi is also a very unique island, possessing a very high biodiversity due to the location on the Wallacea area, and constituting mixing plants from Asia and Australia. An inventory and exploration of orchid in Polewali Mandar Regency was conducted from 25 May to 13 June 2014 to determine and assess the orchid diversity in the area. Orchid specimens were recorded and collected using a purposive random sampling method. A total of 60 accession numbers were collected in the study area. These collections represent 22 genera and 51 species, consists of 41 epiphyte orchids species and 10 terrestrial orchids species. Some species are wide distribute in Indonesia, few of them are only found in eastern part of Indonesia such as Wallacea region, and are even endemic to Sulawesi. Luisia celebica Schltr. and Micropera sterrophylla (Schltr.) Garay are noted as endemic orchid to Sulawesi. While Dendrobium bicaudatum Reinw. ex Lindl., Habenaria beccarii Schltr., Malaxis trigonopetala (J.J.Sm.) S.Thomas, Schuit. & de Vogel and Pinalia quinquangularis (J.J.Sm.) Ormerod are endemic to the Wallacea region mainly in Sulawesi and Moluccas. Among those orchids found in the study, Dendrobium clavator Ridl., Pinalia quinquangularis (J.J.Sm.) Ormerod, and Pinalia xanthocheila (Ridl.) W.Suarez & Cootes are noted as new records in Sulawesi. Many new records of orchids are still to be expected from Sulawesi.

CAM plasticity in epiphytic tropical orchid species responding to environmental stress

BackgroundTo counteract its dramatic species endangerment caused by extensive loss of habitat, Singapore is currently re-introducing into nature some of the native orchids to conserve and improve their germplasm. A main challenge of re-introduction is growing and establishing these plants under natural conditions, which are semi-arid with periodic drought. In this study, six native species were examined, of which three, Bulbophyllum vaginatum, Dendrobium leonis and Phalaenopsis cornu-cervi, are viewed as CAM species while the other three, Coelogyne rochussenii, Coelogyne mayeriana, and Bulbophyllum membranaceum are usually characterized as C3 species. We aimed to compare their physiological responses to drought under two different light conditions: (1) moderate light (photosynthetic photon flux density, PPFD of 900 μmol m−2 s−1) and (2) low light (PPFD < 100 μmol m−2 s−1).ResultsAfter 7 weeks of drought under moderate light (DRML), photosynthetic light utilization was reduced in all six species, and relative water content (RWC) in leaves decreased to < 50% in CAM orchids, compared to > 50% in C3 species, while RWC in pseudobulbs (produced by 4 of the species) fell to < 50%. Both effects were reversed after 14 weeks of re-watering. Proline concentration in leaves increased in the CAM orchids and B. membranaceum (60–130 µmol g−1 FW), and CAM acidity increased (0.2 to 0.8 mmol H+/g fresh weight) in leaves and pseudobulbs of most species including C3 orchids after 7 weeks of DRML, but to lesser extent in B. membranaceum.ConclusionIn the six native orchid species tested, osmoregulation by proline and CAM expression were adaptive responses to maintain photosynthesis under drought stress. Expression of CAM is a significant adaptive mechanism to drought in both C3 and CAM orchids. For C3B. membranaceum, this CAM activity is best described as ‘CAM-idling’. We propose that any future work in understanding adaptive responses in Singapore’s native epiphytic orchids to periodic water deficit should also analyse the significance of CAM plasticity on water conservation within the plant and the regulation of CAM by prevailing water status and light intensity.

The Existence of Genetic Diversity in Maintaining Epiphytic Orchids Germplasm In Pronojiwo Conservation Area, Bromo Tengger Semeru National Park, East Java, Indonesia

Orchids are often found naturally in tropical rainforests. Tropical rainforest destruction could decrease orchid germplasms in the natural habitat. To save their existence, it is necessary to keep them from the threat of extinction. Some efforts that could be done is by conducted periodically exploration and inventory activities. The objective of this research was to revisit the genetic diversity of epiphytic orchid germplasms in Resort Ranu Darungan Pronojiwo Conservation area Bromo Tengger Semeru National Park, East Java compared to the finding in 2002. Exploration of Epiphytic Orchid Diversity at Pronojiwo Conservation Area, Bromo Tengger Semeru National Park, East Java was conducted in January to February 2018. The research method was descriptive-exploration with random sampling method. Exploration results in 2018 found 1.013 orchids population, consisted of 22 genera and 53 species. While in 2002 found 2.053 orchids population, consisted of 18 genera and 39 species. The host trees found in this research was 21, while in 2002 was found 30 host trees. The value of diversity index by Shannon – Wiener in this research was 3.03 (high) and in 2002 was 3.50 (high). Species with the highest population in 2018 was Eria monostachya with the IVI of 32,94%., while in 2002 was Bulbophyllum biflorum with the IVI of 10.84%. From this research, it is concluded that the genetic diversity of epiphytic orchids germplasm in Resort Ranu Darungan is high. Besides time lapse of 16 years, the existence of epiphyte orchids biodiversity is well maintained.

Phylogeography of the Neotropical epiphytic orchid, Brassavola nodosa: evidence for a secondary contact zone in northwestern Costa Rica.

Spatial patterns of genetic variation can reveal otherwise cryptic evolutionary and landscape processes. In northwestern Costa Rica, an approximately concordant genetic discontinuity occurs among populations of several plant species. We conducted phylogeographic analyses of an epiphytic orchid, Brassavola nodosa, to test for genetic discontinuity and to explore its underlying causes. We genotyped 18 populations with 19 nuclear loci and two non-coding chloroplast sequence regions. We estimated genetic diversity and structure, relative importance of pollen and seed dispersal, and divergence time to understand how genetic diversity was spatially partitioned. Nuclear genetic diversity was high with little differentiation among populations (GSTn = 0.065). In contrast, chloroplast haplotypes were highly structured (GSTc = 0.570) and reveal a discontinuity between northwestern and southeastern populations within Costa Rica. Haplotype differences suggest two formerly isolated lineages that diverged ~10,000-100,000 YBP. Haplotype mixing and greater genetic diversity occur in an intermediate transition zone. Patterns of nuclear and chloroplast data were consistent. Different levels of genetic differentiation for the two genomes reflect the relative effectiveness of biotic versus abiotic dispersers of pollen and seeds, respectively. Isolation of the two lineages likely resulted from the complex environmental and geophysical history of the region. Our results suggest a recent cryptic seed dispersal barrier and/or zone of secondary contact. We hypothesize that powerful northeasterly trade winds hinder movement of wind-borne seeds between the two regions, while the multi-directional dispersal of pollen by strong-flying sphinx moths resulted in lower differentiation of nuclear loci.

Germination niches and seed persistence of tropical epiphytic orchids in an urban landscape.

Urbanisation has contributed to significant biodiversity loss, yet, urban areas can facilitate biodiversity conservation. For instance, there is evidence of urban trees supporting natural establishments of orchids, the most species-rich plant family on Earth. However, the germination niches-which include both suitable biophysical conditions and orchid mycorrhizal fungus/fungi (OMF)-are not sufficiently known for most species, especially tropical epiphytic orchids. The fate of their dispersed seeds is poorly understood as well. We conducted fungal baiting and seed sowing experiments, next-generation sequencing, generalised linear models, and seed viability tests to detect and identify potential OMF, investigate biophysical factors that influenced OMF availability and orchid germination, and assess seed longevity. Ceratobasidiaceae- and Serendipitaceae-associated OMF were successfully detected in three of four orchid species. In general, orchid species and humus presence had significant effects on OMF availability. Orchid species and temperature were predictive of germination. Post-experiment viability tests revealed that one orchid species, Grammatophyllum speciosum Blume, may produce long-lived seeds. The results suggest that urban trees can support OMF and orchid germination, but both processes are limited by biophysical factors. This study also indicates the possibility of seed persistence among epiphytic species. As orchid germination niches are complex and tend to be unique to individual species, we do not encourage generalisations. In contrast, species-specific information can help formulate useful recommendations towards conservation.

Aspects of the Pollination Biology of Encyclia tampensis, the Commercially Exploited Butterfly Orchid, and Prosthechea cochleata, the Endangered Clamshell Orchid, in South Florida

Encyclia tampensis (Lindl.) Small (Orchidaceae), the butterfly orchid, is a commercially exploited, epiphytic orchid native to Florida. Similarly, Prosthechea cochleata (L.) W.E. Higgins (Orchidaceae), the clamshell orchid, is an endangered orchid that is epiphytic and native to Florida. We conducted this study in southern Florida at the Florida Panther National Wildlife Refuge to gain more information about the pollination biology of E. tampensis and P. cochleata (var. triandra). Experiments using pollinator exclusion bags revealed that E. tampensis is not capable of spontaneous self-pollination, and requires a pollen vector for seed capsule development; however, P. cochleata appears to be readily self-pollinating. Using active and passive sampling, we determined that E. tampensis potentially can be pollinated by a variety of flower-visiting insects, including Hymenoptera, Diptera, and Coleoptera. Insects from all 3 orders were observed on and collected from the E. tampensis flowers. However, only insects from 1 order (Hymenoptera) were actively collected from P. cochleata. Our data are useful for conservation efforts for E. tampensis and P. cochleata, because knowledge about potential pollinators and self-pollination capability can lead to future studies and information about optimal habitats for outplanting and reintroduction. The orchids face decline due to habitat loss, pests, and poaching, so conservation is an important key to re-establishment of these species.

The impact of life form on the architecture of orchid mycorrhizal networks in tropical forest

Understanding the processes that determine the architecture of interaction networks represents a major challenge in ecology and evolutionary biology. One of the most important interactions involving plants is the interaction between plants and mycorrhizal fungi. While there is a mounting body of research that has studied the architecture of plant–fungus interaction networks, less is known about the potential factors that drive network architecture. In this study, we described the architecture of the network of interactions between mycorrhizal fungi and 44 orchid species that represented different life forms and co‐occurred in tropical forest and assessed the relative importance of ecological, evolutionary and co‐evolutionary mechanisms determining network architecture. We found 87 different fungal operational taxonomic units (OTUs), most of which were members of the Tulasnellaceae. Most orchid species associated with multiple fungi simultaneously, indicating that extreme host selectivity was rare. However, an increasing specificity towards Tulasnellaceae fungal associates from terrestrial to epiphytic and lithophytic orchids was observed. The network of interactions showed an association pattern that was significantly modular (M = 0.7389, Mrandom = 0.6998) and nested (NODF = 5.53, p &lt; 0.05). Terrestrial orchids had almost no links to modules containing epiphytic or lithophytic orchids, while modules containing epiphytic orchids also contained lithophytic orchids. Within each life form several modules were observed, suggesting that the processes that organize orchid–fungus interactions are independent of life form. The overall phylogenetic signal for both partners in the interaction network was very weak. Overall, these results indicate that tropical orchids associate with a wide number of mycorrhizal fungi and that ecological rather than phylogenetic constraints determine network architecture.

Orchids Diversity in the Sicikeh-Cikeh Forest, North Sumatra, Indonesia

Abstract. Hartini S. 2019. Orchids Diversity in the Sicikeh-Cikeh Forest, North Sumatra, Indonesia. Biodiversitas 20: 1087-1096. Sicikeh-cikeh forest includes three forest areas, namely Adian Tinjoan Customary Forest, Adian Tinjoan Protection Forest, and Taman Wisata Alam Sicikeh-cikeh. Typical vegetation of this area is mountain forest with large diversity of plant species. Among the species, orchid is one of the potential plants found diversely in this location and has not yet been recorded. The exploration activities were conducted at Sicikeh-cikeh forest. Orchid exploration was conducted to collect living plants for ex situ conservation purpose. Orchid inventory, to record orchid diversity in this area, was based on plant collection by purposive random sampling. The results of the study recorded approximately 102 different species from 30 genera of orchids in this area. Typical epiphytic and terrestrial highland orchids were found and very common in Sumatra. Among the species found are endemic Sumatra, such as Coelogyne brachygyne, Coelogyne salmonicolor, Dendrobium kruiense, Epigeneium pulchellum, Thrixspermum gombakense, Corybas stenotribonos and Paphiopedilum tonsum. Interesting terrestrial orchids include Kuhlhasseltia javanica, Neuwiedia zollingeri var. javanica, Paphiopedilum tonsum, Phaius callosus, Corybas stenotribonos, Calanthe aurantiaca, Calanthe chrysoglossoides, and Calanthe pulchra. While interesting epiphytic orchids include Bulbophyllum absconditum, Bulbophyllum coloriferum, Coelogyne brachygyne, Epigenium pulchellum, Eria bractescens, Eria pachystachya, Pholidota gibbosa, and Thrixspermum amplexicaule.

Morphological and Molecular Characterization of Orchid Fruit Development.

Efficient seed dispersal in flowering plants is enabled by the development of fruits, which can be either dehiscent or indehiscent. Dehiscent fruits open at maturity to shatter the seeds, while indehiscent fruits do not open and the seeds are dispersed in various ways. The diversity in fruit morphology and seed shattering mechanisms is enormous within the flowering plants. How these different fruit types develop and which molecular networks are driving fruit diversification is still largely unknown, despite progress in eudicot model species. The orchid family, known for its astonishing floral diversity, displays a huge variation in fruit dehiscence types, which have been poorly investigated. We undertook a combined approach to understand fruit morphology and dehiscence in different orchid species to get more insight into the molecular network that underlies orchid fruit development. We describe fruit development in detail for the epiphytic orchid species Erycina pusilla and compare it to two terrestrial orchid species: Cynorkis fastigiata and Epipactis helleborine. Our anatomical analysis provides further evidence for the split carpel model, which explains the presence of three fertile and three sterile valves in most orchid species. Interesting differences were observed in the lignification patterns of the dehiscence zones. While C. fastigiata and E. helleborine develop a lignified layer at the valve boundaries, E. pusilla fruits did not lignify at these boundaries, but formed a cuticle-like layer instead. We characterized orthologs of fruit-associated MADS-domain transcription factors and of the Arabidopsis dehiscence-related genes INDEHISCENT (IND)/HECATE 3 (HEC3), REPLUMLESS (RPL) and SPATULA (SPT)/ALCATRAZ (ALC) in E. pusilla, and found that the key players of the eudicot fruit regulatory network appear well-conserved in monocots. Protein-protein interaction studies revealed that MADS-domain complexes comprised of FRUITFULL (FUL), SEPALLATA (SEP) and AGAMOUS (AG) /SHATTERPROOF (SHP) orthologs can also be formed in E. pusilla, and that the expression of HEC3, RPL, and SPT can be associated with dehiscence zone development similar to Arabidopsis. Our expression analysis also indicates differences, however, which may underlie fruit divergence.

Light quality affects light harvesting and carbon sequestration during the diel cycle of crassulacean acid metabolism in Phalaenopsis.

Crassulacean acid metabolism (CAM) is a specialized photosynthetic pathway present in a variety of genera including many epiphytic orchids. CAM is under circadian control and can be subdivided into four discrete phases during a diel cycle. Inherent to this specific mode of metabolism, carbohydrate availability is a limiting factor for nocturnal CO2 uptake and biomass production. To evaluate the effects of light quality on the photosynthetic performance and diel changes in carbohydrates during the CAM cycle. Phalaenopsis plants were grown under four different light qualities (red, blue, red + blue and full spectrum white light) at a fluence of 100µmol m-2 s-1 and a photoperiod of 12h for 8 weeks. In contrast to monochromatic blue light, plants grown under monochromatic red light showed already a significant decline of the quantum efficiency (ΦPSII) after 5 days and of the maximum quantum yield (Fv/Fm) after 10 days under this treatment. This was also reflected in a compromised chlorophyll and carotenoid content and total diel CO2 uptake under red light in comparison with monochromatic blue and full spectrum white light. In particular, CO2 uptake during nocturnal phase I was affected under red illumination resulting in a reduced amount of vacuolar malate. In addition, red light caused the rate of decarboxylation of malate during the day to be consistently lower and malic acid breakdown persisted until 4h after dusk. Because the intrinsic activity of PEPC was not affected, the restricted availability of storage carbohydrates such as starch was likely to cause these adverse effects under red light. Addition of blue to the red light spectrum restored the diel fluxes of carbohydrates and malate and resulted in a significant enhancement of the daily CO2 uptake, pigment concentration and biomass formation.