Epiphytic Orchid Species Research Articles

Short Communication: Habitat preferences of epiphytic orchids and potential pollinators in Sumber Pawon Forest, Kediri District, East Java, Indonesia

Abstract. Putra SRT, Trisnawati I. 2024. Short Communication: Habitat preferences of epiphytic orchids and potential pollinators in Sumber Pawon Forest, Kediri District, East Java, Indonesia. Biodiversitas 25: 2780-2787. Sumber Pawon Forest, a unique and biodiverse ecosystem in Kediri, Indonesia, is home to approximately 30,000 orchids (family Orchidaceae), which can grow terrestrial or as epiphytes. A diversity of different taxa has been recorded as orchid pollinators. The distribution of epiphytic orchids in this forest is determined by habitat preferences including vertical distribution zone and host tree's characteristics. This research, conducted in the captivating Sumber Pawon Forest, aims to determine habitat preferences influencing the abundance of epiphytic orchids and provide a review of potential epiphytic orchid pollinators. The data were collected by systematic sampling method. Analysis of epiphytic orchids' habitat preferences was done using the ordination method. The study found 3 epiphytic orchids and 5 species of host trees, revealing new insights into their distribution. Epiphytic orchids include Cymbidium sp., Dendrobium crumenatum, and Rhynchostylis retusa. The host trees include Alstonia scholaris, Artocarpus elasticus, Bischofia javanica, Ficus elastica, and Samanea saman. Epiphytic orchids were mainly found in zone 4 rather than in zone 5. The characteristics of host trees, which are preferentially selected by epiphytic orchids, include tree height (ranging from 28.65 to 33.65 m), large DBH (ranging from 165.61 to 175.80 m), and closed canopy cover (ranging from 51 to 75%). One of the pollinator taxa (named Hymenoptera) was found to pollinate epiphytic orchid species, adding to our understanding of their ecological interactions.

Exploration and Characterization of Host Trees and Orchid Epiphyte Zones in Lore Lindu National Park, Central Sulawesi

Host trees are vital for the survival of epiphytic orchids, providing necessary light and air circulation for optimal growth. Large trees with tall canopies contribute to the broader distribution of epiphytic orchids in forest areas. This research aimed to identify the characteristics of orchid host tree species in Lore Lindu National Park, considering both elevation zones and orchid growth zones. The research was conducted at various locations within the park, employing the field exploration survey method (cruise method). This method involved comprehensive exploration at each research site and establishing observation paths along pioneer lines, mainly where orchid host trees were found. The findings indicate the presence of 20 types of orchid host trees and 35 species of epiphytic orchids. The basal branching zone (Zone 3) was the most populated by epiphytic orchids on host trees, and the lowland forest was the elevation zone where most orchid host trees were found in Lore Lindu National Park, Central Sulawesi. Keywords: host trees, Lore Lindu National Park, orchids, zone distribution

Associations between Epiphytic Orchids and Their Hosts and Future Perspectives of These in the Context of Global Warming

Epiphytic species are ecologically important and a significant component of biodiversity. To ensure their efficient conservation, we need to understand their ecology and host plant associations. It is also important to investigate how the predicted temperature change will affect their future distribution. Here, we use data collected in Nepal to investigate how epiphytic orchids are associated with host species, their distribution patterns, and how they may be threatened by the predicted increase in temperature towards the end of the 21st century. We used the phi coefficient (Φ) of association to calculate the associations of epiphytic orchid species with plants and rarefaction to describe the diversity of orchids associated with a particular host species. We used interpolation to estimate the distribution of epiphytic orchids and their host species along altitudinal gradients. The phi (Φ) coefficient of association revealed that 30 species of host plants showed more association with different orchid species than expected. The number of epiphytic orchids increased with the number of host individuals. We predict that an increase in temperature by ~3 °C, which is a more moderate value of temperature increase by the end of the 21st century, will affect at least 52 narrow-ranged species of orchids and 58 narrow-ranged species of host plants. Therefore, we should make efforts to prevent many plant species from becoming extinct, as an increase in temperature is likely to affect their existence.

KEANEKARAGAMAN JENIS ANGGREK DI JALUR PENDAKIAN WIRAYANA GUNUNG CAKRABUANA KABUPATEN MAJALENGKA

The existence of orchids in nature continues to decline due to habitat destruction and overexploitation. Conservation efforts that have been carried out so far have often experienced difficulties due to insufficient data and information as a basis for management, including conservation areas. The more widespread forest destruction will result in these species being threatened with extinction. This study aims to determine the diversity of orchid species, on the Wirayana Mount Cakrabuana Climbing Path. The information is expected to provide an initial contribution to the area management and orchid conservation efforts on the Wirayana Mount Cakrabuana Climbing Path. This research was conducted by means of a vegetation survey, sampling and documentation by exploring the existence of orchids. The sampling technique used the path transect method. The number of transects used is one line transect with a line length of 1500 m with a total of 22 sample plots. Data analysis was carried out by calculating the Important Value Index (INP), Species Dominance Index (Di) and Species Diversity Index (H'). The results showed that in the natural forest area of ​​Mount Cakrabuana there were 22 species of individuals which included 7 species of terrestrial orchids and 15 species of epiphytic orchids with a total of 243 individuals found. From the results of the calculation of species diversity, it is stated that the diversity of orchid species in the natural forest area of ​​Mount Cakrabuana is classified as moderate (2,973). This information is very important, especially for area managers in preserving the biodiversity of Mount Cakrabuana, especially orchids in the future.

Inventory of Orchid Species in Customary Forest Area of Cipta Karya Village, Sungai Betung District, Bengkayang Regency

Orchids are one of the flowering plants that have many species and are widely distributed, as well as having different attractions and characteristics in each species and habitat. The aim of this research to inventory the types of orchids in Customary Forest Area of Cipta Karya Village, Bengkayang Regency. The research was conducted using the cruise method. The characteristics observed were the morphology of orchids such as roots, pseudobulbs, stems, leaves, and flowers. The inventory results found 13 species of orchids. Epiphytic orchids were found more commonly in this area, with a total of 9 species, while terrestrial orchids were found with 4 species. The epiphytic orchid species foundware composed of Appendicula sp., Bulbophyllum sp., Coelogyne speciosa, Cymbidium sp., Dendrobium crumenatum, Dendrobium anosmum, Luisia sp., Micropera pallida and Oberonia sp. The terrestrial orchid species found ware composed of Acanthephippium javanicum, Malaxis latifolia, Nephelaphyllum pulchrum, and Spathoglottis plicata.

Ancient tea gardens play important role on in situ conservation of epiphytic orchids in southwest Yunnan, China

Southwest Yunnan of China is the homeland of famous Pu’er tea and preserved the largest area of ancient tea gardens in the world. The ancient tea gardens keeping a large number of shade trees have prevailed for hundreds of years persist and formed typical agroforestry systems. To assess the potential of the ancient tea gardens for in situ orchid conservation, in this study, three typical ancient tea gardens located at different elevations, JiNuo Mountain ancient tea garden (JNM, 1150 m asl.), JingMai Mountain ancient tea garden (JMM, 1345 m asl.), and LaoBanZhang ancient tea garden (LBZ, 1787 m asl.), were selected to investigate species diversity and composition, and conservation status of all orchids. Floral visitors, reproductive success, and seedling recruitment of selected epiphytic orchids were also investigated from 2019 to 2021. We identified 88 orchid species (85 epiphytic and 3 terrestrial orchids) in 33 genera in the three ancient tea gardens, including one critically endangered species (CR), four endangered species (EN) and 16 vulnerable species (VU). Although the orchid species diversity was not significantly different, the species composition varied greatly among the three ancient tea gardens. For the randomly selected 40 epiphytic orchid species, all species could set fruits naturally, and the natural fruit-sets ranged from 1.11 ± 6.0% to 62.07 ± 15.4% with great variations among species and years. For 60 epiphytic orchid species observed, seedling recruitment for 26 species (43.3%) were observed and confirmed. Among 42 insect visitors observed, 21 species including bees, flies and ants, were confirmed as effective pollinators to 16 epiphytic orchids. These results revealed that the ancient tea gardens maintained high species diversity of epiphytic orchids and provided pollinator services for reproductive success and suitable micro-environment for seed germination and seedling recruitment. We strongly suggested that the ancient tea gardens in the area could serve as important supplements for in situ conservation of epiphytic orchids.

KARAKTERISTIK POHON INANG DAN KEANEKARAGAMAN ANGGREK (Orchidaceae) EPIFIT DI HUTAN LINDUNG LUNUNIANAM, DESA FATU’ULAN, KECAMATAN KI’E, KABUPATEN TIMOR TENGAH SELATAN, PROVINSI NUSA TENGGARA TIMUR

This study was conducted to determine the characteristics of orchid host trees, the diversity of epiphytic orchids (Orchidaceae), and the preservation of host trees and epiphytic orchids in the Lununianam protected forest area. This research was conducted in Lununianam Protection Forest, Fatu'ulan Village, Ki'e District, South Central Timor Regency, East Nusa Tenggara Province. Which is carried out for 1 month, from November to December 2022. This study used purposive sampling methods, surveys, and cruising paths with data analysis using qualitative descriptive and quantitative descriptive analysis. Host tree data was processed using vegetation analysis formulas and orchid data was processed using the Shannon wiener (H') diversity index formula.
 The results showed that there were 5 species of host trees found in the study site, namely forest guava (Syzygium pycnanthum), Matani (Pterocarpus indicus), Tahi (Celtis wightii planch), Kamala (Mallotus philippensis), Jenitri (Elaeocarpus ganitrid). Host trees found in Lununianam Protection forest have the characteristics of large hard and rough bark, have a height range of 12-30 m, and bark overgrown with moss, The results of vegetation analysis of host tree species with the highest Important Value Index namely Syzygium Pycnanthum and Elaeocarpus ganitrus have the lowest Important Value Index. Orchids found in the sampling plot in the Lununianam Protection Forest contained 8 species of epiphytic orchids, namely Dendrobium Sp, Vanda insignis, Eria multiflora, Flickingeria grandiflora, Trichoglottis bipenicillata, Pholidota carnea, Appendicula reflexa Blume, and Ceologyne speciosa. The calculation of Shannon Wiener's diversity index of 1.57 (H') is classified as medium (1<H'<3). The most common type of orchid found is the type Eria multifora with a total of 168 individuals and the type that is less commonly found is Appendicula reflexa Blume with 4 individuals.

Megasporogenesis, megagametogenesis and embryogenesis of Liparis elliptica (Orchidaceae), with special note to the development of unique unitegmal ovule.

Megasporogenesis, megagametogenesis and embryogenesis of Liparis elliptica (family Orchidaceae, tribe Malaxideae, subtribe Malaxidinae) have been studied. It was shown that the L. elliptica embryo sac is monosporic and develops from the chalazal cell of the megaspore triad according to the modified Polygonum type. The embryo sacs are reduced to four-six nuclei. The suspensor is unicellular, spherical in shape, originating from the basal cell (cb). A unique feature of L. elliptica is the unitegmal ovule, which distinguishes this species from other members of the tribe Malaxideae. The seed coat is formed by an outer layer of the single internal integument. Reduction of the outer integument is a rare feature for epiphytic orchid species with photosynthetic leaves.

Morphological, stomatal, pigmentation, and biomolecular characteristics of a few epiphytic orchid species of India

In order to identify suitable species that can be used for cross-breeding and propagation for horticulture purposes four endemic and epiphytic orchid species, Aerides crispa Lindl., A. maculosa Lindl., A. ringens Fischer. and A. odorata Lour. were studied by comparing their leaf morphology, stomata, pigmentation, and biomolecules. Standard methods were used for the evaluation. A. odoratum, native to the lowest altitude, was characterized by thin, long leaves with the lowest specific leaf area and higher water content. Among the four species studied, stomata were bigger in size and less in number in A. odoratum. Maximum total soluble sugars, soluble proteins, amino acids, and starch contents, an indicator of a better photosynthesis rate were noted in A. odoratum. Total chlorophyll and carotenoid contents per unit leaf area were higher in A. odoratum and A. ringens. Our results concluded that variation in environmental temperature, humidity, sunlight intensity, and exposure of orchids at different altitudes may cause alteration in traits that can be inherited over a period.

Invitro and Mass Multiplication of Cymbidium mastersii an Ornamental Orchid through Protocorm-like Body Formation

The epiphytic orchid species known as Cymbidium mastersii can only be found in the region of India known as Northeast India. The preservation of wild populations faces a significant obstacle in the form of a significant threat when it comes to the necessity of obtaining an additional source of the material required to fulfil commercial demands. The objective of this research was to build an in vitro system for the bulk multiplication of C. mastersii, and it was successful in that endeavour. This required the capacity to control the growth of the seedlings through the development of the primary protocorm and germination from a limited number of fruit capsules. Also necessary was the ability to limit the amount of fruit capsules that could be used. Each protocorm resulted in the production of a number of robust plantlings that, once they had been separated from their mother plant, flourished in the conditions of the greenhouse. The child plants, in terms of both their size and the development they underwent, were genetically identical to their parent plant. The streamlined process will make it possible to cultivate Cymbidium mastersii for use in the commercial sector, which will reduce the negative influence on remaining viable wild populations. We offer here for the very first time a method of producing C. mastersii on a commercial scale that makes use of bioreactor technology.

Mycorrhizal specificity differences in epiphytic habitat: three epiphytic orchids harbor distinct ecological and physiological specificity.

Orchidaceae has diversified in tree canopies and accounts for 68% of vascular epiphytes. Differences in mycorrhizal communities among epiphytic orchids can reduce species competition for mycorrhizal fungi and contribute to niche partitioning, which may be a crucial driver of the unusual species diversification among orchids. Mycorrhizal specificity-the range of fungi allowing mycorrhizal partnerships-was evaluated by assessment of mycorrhizal communities in the field (ecological specificity) and symbiotic cultures in the laboratory (physiological specificity) for three epiphytic orchids inhabiting Japan. Mycorrhizal communities were assessed with co-existing individuals growing within 10cm of each other, revealing that ecological specificity varied widely among the three species, ranging from dominance by a single Ceratobasidiaceae fungus to diverse mycobionts across the Ceratobasidiaceae and Tulasnellaceae. In vitro seed germination tests revealed clear differences in physiological specificity among the three orchids, and that the primary mycorrhizal partners contributed to seed germination. In vitro compatibility ranges of three orchids strongly reflect the mycorrhizal community composition of wild populations. This suggests that differences in in situ mycorrhizal communities are not strongly driven by environmental factors, but are primarily due to physiological differences among orchid species. This study shows that the symbiotic strategy among the epiphytic orchid species varies from specialized to generalized association, which may contribute to biotic niche partitioning.

Seed Morphology of Three Neotropical Orchid Species of the Lycaste Genus

Neotropical orchids are vulnerable to extinction due to overharvesting, habitat destruction and climate change. However, a basic understanding of orchid seed biology to support conservation efforts is still lacking for most species. Seed morphology is linked to plant adaptation and evolution, influencing seed dispersal, dormancy, longevity, and germination, which are valuable traits for conservation. In this study, we characterized and compared the morphological traits of seed capsules (size, shape, and colour) and seeds (seed and embryo shape and size and internal airspace volume) for three epiphytic Neotropical orchid species of the genus Lycaste native to Guatemala: L. cochleata, L. lasioglossa, and L. virginalis. The three species show qualitative similarities in seed capsule colour and appearance and in seed morphology (i.e., scobiform oval-shaped seeds and prolate-spheroid embryos). All species have small-sized seeds (length of L. cochleata: 210 µm, L. lasioglossa: 230 µm, and L. virginalis: 260 µm), with proportionally large embryos (length of L. cochleata: 140 µm, L. lasioglossa: 120 µm, and L. virginalis: 150 µm) and an internal air-space volume that occupies less than half of the seed (L. cochleata: 17%, L. lasioglossa: 42%, and L. virginalis: 30%). This finding is consistent with previous reports for other epiphytic orchid species, which typically have lower air volumes than terrestrial orchids. These differences are likely a result of evolutionary changes associated with different habits and may influence seed dispersal. We also found some significant differences in seed morphology between the studied species, but their taxonomic, biological, and ecological relevance remain to be elucidated. More comparative studies, including on other Lycaste species with different habits, are needed to explore relationships between seed morphology, taxonomy, biology, and ecology in this genus to support its conservation.

The epiphytic orchid Vanda falcata is predominantly associated with a single Tulasnellaceae fungus in adulthood, and Ceratobasidiaceae fungi strongly induce its seed germination in vitro

AbstractVanda falcata is an epiphytic orchid native to East Asia with high horticultural and ornamental value. However, its wild populations are at risk of extinction due to overcollection and habitat loss. Orchids are highly dependent on mycorrhizal fungi for their nutrient acquisition from seed germination to adulthood; therefore, understanding their mycorrhizal associations throughout the life cycle is essential for their conservation. We investigated the mycorrhizal fungi of adult V. falcata plants through the molecular identification of root samples from 40 individual plants from 13 sites, covering a distance of 1200 km across Japan. To identify the fungi that promote V. falcata seed germination, we performed seed germination tests in vitro with fungal isolates from V. falcata and other epiphytic orchids. In adult plants, we detected a total of 11 operational taxonomic units (OTUs) within two fungal families, Ceratobasidiaceae and Tulasnellaceae, and a single Tulasnellaceae OTU (TU11) was found in samples from 12 sites. However, Vanda falcata seed germination and early development were induced in vitro by Ceratobasidiaceae fungi rather than Tulasnellaceae fungi, including TU11. These results suggest that different mycorrhizal fungi may be predominantly associated with V. falcata in the adult and seed germination stages. This mycorrhizal switching suggests that effective mycorrhizal fungi for conservation may differ between the adult and juvenile stages, even within a single orchid species. Our findings clarify the mycorrhizal associations of endangered epiphytic orchid species and could improve conservation efforts for these rare plants.

Diversity of EPIFIT Orchid Types in the Mangrove Ecosystem in Ayari Village, Teluk Ampimoi Sub District, Yapen Islands District, Papua Province, Indonesia

This research was conducted in Ayari village, Teluk Ampimoi sub District, Yapen Islands District for approximately two months or from November to October. The research objective was to determine the types of epiphytic orchids and their presence. The method used in this research is descriptive method with observation and documentation techniques. The results of this study found as many as 6 genera consisting of 16 species of epiphytic orchids, which grow on 3 types of mangroves. There are environmental factors that affect the distribution of mangroves that can have an indirect effect on orchids, namely: salinity, sunlight intensity and wind speed.

Habitat Ecology, Structure Influence Diversity, and Host-Species Associations of Wild Orchids in Undisturbed and Disturbed Forests in Peninsular Malaysia

As an attempt to examine the causes of forest disturbance and degradation of the orchid community, a comparative study on diversity and ecology in eight undisturbed and ten disturbed forests in Peninsular Malaysia was conducted that varied in areas, elevations, vegetation types, and disturbance regimes. Density and individual-based rarefaction curves were used to describe the abundance. Univariate and multivariate analyses were also performed to explore the associations of species abundance with biotic and abiotic factors. The study reported 239 orchid species belonging to 65 genera. Species richness, abundance, density, and diversity of orchids varied by locality. Higher density of orchids (2.433 plants/km2) occurred in the undisturbed forests than in the disturbed forests (0.228 plants/km2). As with the character of undisturbed forests, the temperature was between 27.8 ± 0.3 °C and 31.2 ± 0.2 °C, humid (77.1 ± 1.2%–89.6 ± 0.9%), and with low light intensity (23.8 ± 3.3 μmol m−2s−1–171.7 ± 18.8 μmol m−2s−1), thus supporting the high density of the plants. Disturbed forests had higher diversity (H = 4.934 and 1-D = 0.990) and abundance (183 species of 57 genera) but were determined to be highly influenced by the higher abundance of epiphytic orchids on the fallen trees and ease of accessibility in the logged forests. Terrestrial and mycoheterotroph orchids were much lower in density and abundance in the disturbed habitat indicating a gradual reduction in their niche availability following the disturbance. Additionally, the ecology data show that the microclimate conditions of the canopy-covered forest was influenced by proximity to the logged area which had eventually reduced the orchids’ habitat quality. Furthermore, the results show that the abundance of epiphytic orchid communities was associated with the host plant characteristics. Host types and bark texture preference were apparent for the epiphytic orchid species, with certain types and textures hosting more orchid species than others. Overall results show that extreme temperature, humidity, and light intensity caused by the canopy opening inflicted damages to the habitat conditions and bark textures of the host plants and limits recolonisation of the orchids in the disturbed forests. The species diversity and density patterns of orchids in undisturbed and disturbed forests revealed in this study provide a baseline for conservationists, policy makers, and forest authorities in expanding the understanding of the forest ecology and vegetation along the disturbance gradient, forest regeneration, and criteria for plant selection for forest restoration in Peninsular Malaysia.

Genetic diversity and structure in two epiphytic orchids from the montane forests of southern Ecuador: The role of overcollection on Masdevallia rosea in comparison with the widespread Pleurothallis lilijae.

Ecuador has a high diversity of orchids, but little is known about levels of genetic diversity for the great majority of species. Understanding how orchids might adapt to changes is crucial as deforestation and fragmentation of forest ecosystems threaten the survival of many epiphytic orchids that depend on other species, such as fungi and their host trees, for germination, growth, and establishment. Overcollection and the illegal trade are also major concerns for the survival of wild populations of orchids. Despite increasing awareness, effective interventions are often limited by a lack of data concerning the impacts that overexploitation might have. To fill this gap, we tested the effects of overcollection in the genetic diversity and structure of Masdevallia rosea, a narrow distributed epiphytic orchid historically collected in Ecuador, in comparison with the widely distributed Pleurothallis lilijae. Genotyping based on AFLPs showed reduced levels of diversity in wild populations but most especially in the overcollected, M. rosea. Overall, genetic admixture was high in P. lilijae segregating populations by altitude levels while fewer genetic groups were found in M. rosea. Genetic differentiation was low in both species. A spatial genetic structure was found in P. lilijae depending on altitude levels, while no spatial genetic structure was found in M. rosea. These results suggest different scenarios for the two species: while gene flow over long distance is possible in P. lilijae, the same seems to be unlikely in M. rosea possibly due to the low levels of individuals in the known populations. In situ and ex situ conservation strategies should be applied to protect the genetic pool in these epiphytic orchid species, and to promote the connectivity between wild populations. Adopting measures to reduce overexploitation and to understand the impacts of harvesting in wild populations are necessary to strengthen the legal trade of orchids.

Collateral damage: epiphytic orchids at risk from myrtle rust

Epiphytic orchids rely on the habitat provided by their plant hosts to survive. The naturalisation of Austropuccinia psidii (G. Winter) Beenken (the causal agent for myrtle rust) in Australia means that some of these plant hosts, from the family Myrtaceae, are at risk of serious decline. We aimed to identify orchid species that associate with myrtaceous host plants and determine which, if any, might be susceptible to loss of habitat as a result of myrtle rust. We reviewed species descriptions and herbarium records and identified 73 epiphytic orchid species that are commonly found growing on myrtaceous hosts. At least seven orchid species are predominantly reliant on myrtaceous hosts, are distributed predominantly in the myrtle rust zone, and have host species that are highly or extremely susceptible to myrtle rust. Four of these orchid species are already listed as threatened. The impact of myrtle rust is broader than causing decline of Myrtaceae species, with knock-on effects on other biota, including epiphytic orchids. Moreover, there is the potential for further impact on these orchids through fragmentation (e.g. affecting pollination) and interactive effects with fire. Increased effort is required to identify the relative frequency of myrtaceous and non-myrtaceous hosts for these epiphytic orchid species, especially in relation to the compound effects of myrtle rust and other perturbations, such as fire and climate change. Where this is not possible, ex situ conservation may be required.

Host tree species effects on long-term persistence of epiphytic orchid populations

The destinies of epiphytic orchids (about 70% of all orchids) are linked to their host trees. However, there is little information on if differences in host trees characteristics can affect the long-term persistence of orchid populations, and how this might vary under different climatic conditions. We compared the population dynamics of two epiphytic orchid species, Alamania punicea and Oncidium brachyandrum growing on two host trees with contrasting leaf phenologies: the deciduous Quercus martinezii and the semideciduous Q. rugosa, over 3 years with varying levels of rainfall, in a montane tropical oak forest in Oaxaca, Mexico. Using data from > 500 individuals growing on 63 host trees, we applied linear mixed effects models, Integral Projection Models, and Life Table Response Experiments to identify the effects of host tree on orchid vital rates and population growth rates. For both orchid species, survival and growth did not differ between host species during wettest year. However, during the driest year both vital rates were higher on the semi-deciduous host Q. rugosa than on the deciduous Q. martinezii. Host species did not affect fecundity for A. punicea, but for O. brachyandrum fecundity was higher on the deciduous host. For A. punicea, λ values were similar between hosts during the wettest and intermediate years, but significantly lower (Δ λ = 0.28) on the deciduous than on the semi-deciduous host during the driest year. This was due primarily to lower survival on the deciduous host. For O. brachyandrum, λ was slightly higher (Δ λ = 0.03) on the deciduous than the semideciduous host during the wettest year, due to higher growth and reproduction. However, during the intermediate and driest years, λ values were significantly higher on the semi-deciduous than on the deciduous host (Δ λ = 0.13 and 0.15, respectively). This was due to higher survival and growth. A. punicea populations appear more vulnerable to dry conditions than O. brachyandrum, likely due to its smaller pseudobulbs, and hence lower water-storing capacity. Our results show that host tree species can both influence the vital rates and the long-term dynamics of orchid populations, and these effects vary across orchids species and over time. Our results highlight the importance of maintaining a diversity of host trees to ensure long-term population persistence.

Phylogenetic affiliation of endophytic actinobacteria associated with selected orchid species and their role in growth promotion and suppression of phytopathogens.

Endophytic actinobacteria aid in plant development and disease resistance by boosting nutrient uptake or producing secondary metabolites. For the first time, we investigated the culturable endophytic actinobacteria associated with ten epiphytic orchid species of Assam, India. 51 morphologically distinct actinobacteria were recovered from surface sterilized roots and leaves of orchids and characterized based on different PGP and antifungal traits. According to the 16S rRNA gene sequence, these isolates were divided into six families and eight genera, where Streptomyces was most abundant (n=29, 56.86%), followed by Actinomadura, Nocardia, Nocardiopsis, Nocardioides, Pseudonocardia, Microbacterium, and Mycolicibacterium. Regarding PGP characteristics, 25 (49.01%) isolates demonstrated phosphate solubilization in the range of 61.1±4.4 - 289.7±11.9 µg/ml, whereas 27 (52.94%) isolates biosynthesized IAA in the range of 4.0 ± 0.08 - 43.8 ± 0.2 µg/ml, and 35 (68.62%) isolates generated ammonia in the range of 0.9 ± 0.1 - 5.9 ± 0.2 µmol/ml. These isolates also produced extracellular enzymes, viz. protease (43.13%), cellulase (23.52%), pectinase (21.56%), ACC deaminase (27.45%), and chitinase (37.25%). Out of 51 isolates, 27 (52.94%) showed antagonism against at least one test phytopathogen. In molecular screening, most isolates with antifungal and chitinase producing traits revealed the presence of 18 family chitinase genes. Two actinobacterial endophytes, Streptomyces sp. VCLA3 and Streptomyces sp. RVRA7 were ranked as the best strains based on PGP and antifungal activity on bonitur scale. GC-MS examination of ethyl acetate extract of these potent strains displayed antimicrobial compound phenol, 2,4-bis-(1,1-dimethylethyl) as the major metabolite along with other antifungal and plant growth beneficial bioactive chemicals. SEM analysis of fungal pathogen F. oxysporum (MTCC 4633) affected by Streptomyces sp. VCLA3 revealed significant destruction in the spore structure. An in vivo plant growth promotion experiment with VCLA3 and RVRA7 on chili plants exhibited statistically significant (p<0.05) improvements in all of the evaluated vegetative parameters compared to the control. Our research thus gives insight into the diversity, composition, and functional significance of endophytic actinobacteria associated with orchids. This research demonstrates that isolates with multiple plant development and broad-spectrum antifungal properties are beneficial for plant growth. They may provide a viable alternative to chemical fertilizers and pesticides and a sustainable solution for chemical inputs in agriculture.

In Vitro Florigenesis with Special Reference to Orchids- A Review.

Orchids are widely used in floriculture as attractive cut flowers all over the world. The current paper reviews factors affecting the in vitro flowering in orchid species. The phenomenon of in vitro flowering is advantageous as it shortens the breeding cycle, which is prolonged in the in vivo grown orchid species of commercial value. Certain genetic and biochemical mechanisms are involved at the time of onset of flowering in orchid plants. In the present endeavour, efforts have been made to initiate in vitro flowering in terrestrial and epiphytic orchid species. Various phenomenon involved during transition of vegetative shoot apex into floral axis is also reviewed. In vitro flowering was induced in Dendrobium nobile and Zeuxine strateumatica in Mitra medium supplemented with BAP at 0.5 in mgl-1. In vitro flowering can be initiated by manipulating physical and chemical stimulus in the nutrient regime. The study would be helpful in better understanding the complex process of flowering in vitro as well as ex vitro.