Orchid Roots Research Articles

Spatiotemporal dynamics and functional characteristics of the composition of the main fungal taxa in the root microhabitat of Calanthe sieboldii (Orchidaceae)

BackgroundEndophytic fungi play a critical ecological role in the growth and development of orchids, but little is known about the spatial and temporal dynamics of fungal diversity or the ecological functions of fungi during orchid growth and reproduction. Calanthe sieboldii Decne. is listed in the Chinese National Key Protected Wild Plants as a class I protected wild plant. To understand the community characteristics of root and soil fungi of the orchid during its reproductive seasons, we investigated the community composition, spatial and temporal dynamics, and functional characteristics of the orchid microhabitat fungi by using diversity and ecological functional analyses.ResultsWe discovered that there were three, seven, and four dominant fungal families in the orchid's roots, rhizoplane soil, and rhizosphere soil, respectively. Tulasnellaceae, Aspergillaceae, and Tricholomataceae were the dominant fungi in this endangered orchid's microhabitats. The closer the fungal community was to the orchid, the more stable and the less likely the community composition to change significantly over time. The fungal communities of this orchid's roots and rhizoplane soil varied seasonally, while those of the rhizosphere soil varied interannually. Saprophytic fungi were the most abundant in the orchid's fungal community, and the closer the distance to the orchid, the more symbiotic fungi were present.ConclusionsThe fungi in different parts of the root microhabitat of C. sieboldii showed different spatiotemporal dynamic patterns. The fungal community near the orchid roots was relatively stable and displayed seasonal variation, while the community further away from the roots showed greater variation. In addition, compared with the soil fungi, the dominant endophytic fungi were more stable, and these may be key fungi influencing orchid growth and development. Our study on the spatiotemporal dynamics and functions of fungi provides a basis for the comprehensive understanding and utilization of orchid endophytic fungi.

Adaptational Mechanisms of Epiphytic Orchids: A Review

Orchidaceae belongs to the 84 families of vascular plants that cover species following the epiphytic life pattern. Adaptations are specialized mechanisms that permit a plant or animal to live in a particular area or habitat. Adaptational mechanisms in plant morphology are essential for the transition to an epiphytic canopy habitat. Orchids have specific adaptational mechanisms in the roots, stems, leaves, flowers, seed and other physiological processes. Under water scarcity, these orchids have developed pseudobulbs, an energy, water, and nutrient storage bulb for adaptations.A wax coating covering the surface of the leaf, also prevents evaporation and gas exchange in drier or hotter climate.Epiphytic orchids have adequate root systems to enable them to grow in a poor nutrient environment when they grow at slow rate. In such cases, velamen of orchids helps to absorb water and also help to absorb nutrients from rainfall. Orchid roots are adapted to cling to trees. Orchid seeds do not have endosperm and require a fungal association with mycorrhiza to provide its energy till the development of roots and leaves. This symbiotic feature is another adaption to make the orchid seed to travel longer and further distances for survival. In comparison to the activity of C3 photosynthesis, crassulacean acid metabolism (CAM) in many epiphytes plays a vital role in improving carbon gains and water use. In this review, specialized adaptations of some commercial orchid genera namely Dendrobium, Cymbidium, Phalaenopsis, Cattleya, Oncidium, Epidendrum and Paphiopedilum are discussed in detail.

Mycorrhizal diversity and community composition in co-occurring Cypripedium species.

Orchids commonly rely on mycorrhizal fungi to obtain the necessary resources for seed germination and growth. Whereas most photosynthetic orchids typically associate with so-called rhizoctonia fungi to complete their life cycle, there is increasing evidence that other fungi may be involved as well and that the mycorrhizal communities associated with orchids may be more diverse. Coexisting orchid species also tend to associate with different fungi to reduce competition for similar resources and to increase long-term population viability. However, few studies have related the mycorrhizal communities in the rhizosphere to communities found in the roots of closely related coexisting orchid species. In this study, we used high-throughput sequencing to investigate the diversity and community composition of orchid mycorrhizal fungi in the roots and the rhizosphere of four Cypripedium species growing in forests in Northeast China. The results showed that the investigated Cypripedium species associated with a wide variety of fungi including members of Tulasnellaceae, Psathyrellaceae, and Herpotrichiellaceae, whereas members of Russulaceae, Cortinariaceae, Thelephoraceae, and Herpotrichiellaceae showed high abundance in rhizosphere soils. The diversity of fungi detected in the rhizosphere soil was much higher than that in the roots. The observed variation in fungal communities in Cypripedium roots was not related to forest site or orchid species. On the other hand, variation in mycorrhizal communities of rhizosphere soil was significantly related to sampling site. These results indicate that orchid mycorrhizal communities in the rhizosphere display considerable variation among sites and that orchids use only a subset of the locally available fungi. Future studies focusing on the fine-scale spatial distribution of orchid mycorrhizal fungi and more detailed assessments of local environmental conditions will provide novel insights into the mechanisms explaining variation of fungal communities in both orchid roots and the rhizosphere.

Structure and diversity of mycorrhizal fungi communities of different part of Bulbophyllum tianguii in three terrestrial environments.

Mycorrhizal fungi plays important roles in the seed germination and subsequent growth of orchids. The research of fungi in orchid roots, especially dominant mycorrhizal fungi is critical for orchids protection. In this study, the fungal community and composition of mycorrhizal fungi in roots, rhizomes and rhizosphere soil of Bulbophyllum tianguii grown in three terrestrial environments were analyzed by the second generation sequencing technology. The results of OTU clustering and α and β diversity analysis showed that there were significant differences in fungal communities in roots, rhizomes and rhizosphere soil of B. tianguii. The total number of OTUs in rhizomes was much less than that in roots and rhizosphere soil. The number of OTUs in rhizosphere soil and the diversity of mycorrhizal fungi were the highest. Meanwhile, the species and abundance of mycorrhizal fungi in roots and rhizomes of B. tianguii were different from those in rhizosphere soil. For different elevations, compared with B. tianguii that grow in middle of Tiankeng and top of Tiankeng, the OTUs number of B. tianguii in orchid garden is richest, and the diversity of mycorrhizal fungi in orchid garden was significantly higher than other locations. Among the three different habitats of B. tianguii, the number of OTUs in humus soil and stone habitats was notably higher than tree habitats, and the diversity of mycorrhizal fungi in humus soil was the highest. The analysis of mycorrhizal fungi in different habitats and altitudes of B. tianguii showed that Sebacina and Exophiala were the dominant mycorrhizal fungi in B. tianguii. The results of species annotation, phylogenetic tree and co-occurrence network analysis showed the dominant mycorrhizal fungi of B. tianguii mainly included Sebacina, Cladosporium, Exophiala, Fusarium. This study reveals the symbiotic relationship between Sebacina, Exophiala, Cladosporium and the B. Tianguii. It will provide a theoretical basis for the protection and biological function study of B. Tianguii.

Aklimatization Black Orchid Plantlets (Coelogyne pandurata Lindl.) with Biostimulant Moringa Leaf Extract (Moringa oleifera Lamk.)

The growth of black orchid plantlets (Coelogyne pandurata Lindl.) are slow at the acclimatization stage. An alternative was used moringa leaf extract (Moringa oleifera Lamk.) as a biostimulant. The aim of this research to find out the effect of giving moringa leaf extract on the growth of black orchid plantlets at the acclimatization stage and to obtain the best concentration and timing of extract to increase the growth of black orchid plantlets. The research used a factorial completely randomized design (FCRD) method with two factors. Factor I is the concentration of the extract which consists of 5 levels, namely 0, 25, 50, 75 and 100 mg/L. Factor II is the application time which consists of 2 levels, namely once a week and every 2 weeks, each treatment is repeated 5 times. The results showed that moringa leaf extract had a significant effect on the mean leaf width and number of plantlet roots of black orchids. Extract concentration of 50 mg/L was the best concentration on the growth of black orchid plantlets with an average leaf width of 0.76 cm and an average root number of 8.2. Recommended for the acclimatization of black orchids to use extract concentration 50 mg/L.

Spatial turnover of fungi and partner choice shape mycorrhizal networks in epiphytic orchids

Abstract In soils, plants and fungi can form complex mycorrhizal networks allowing nutrient transfers between plant individuals and species. It is less clear, however, whether such networks exist on the bark of trees where epiphytic plant communities thrive in rainforests. Previous work showed that tropical epiphytic orchids especially, harbour symbiotic fungi in their roots, but the structure and determinants of the resulting networks remain unknown at the tree scale. We tested the hypothesis that epiphytic orchids rooted in the same area on the bark share mycorrhizal fungi, regardless of their species (i.e. spatial determinant). For this purpose, we selected the trunk of six trees of two common species in a rainforest and sampled orchid roots, protocorms and surrounding bark. We identified mycorrhizal fungi including Tulasnellaceae using high‐throughput sequencing of the ITS2 marker, and reconstructed orchid–fungus bipartite networks for each tree to analyse their structure and the spatial turnover of this symbiosis. We found that epiphytic orchid communities form antinested and highly modular networks with mycorrhizal fungi spread on the bark. As expected, modules of interactions are explained by their spatial structure, with nearby roots sharing fungi, but also by the orchid species involved. These results reveal the presence of shared mycelial networks in epiphytic habitats, whose roles in the resilience and facilitation of epiphytic plant communities need to be assessed. Synthesis. Tropical tree barks are densely colonized by certain mycorrhizal fungi that can form symbioses in nearby adult and young orchids simultaneously. These mycorrhizal networks may allow water and nutrient transfers to alleviate the stressful conditions of the epiphytic habitats.

The Acclimatization Stage Growth Of Black Orchid (Coelogyne Pandurata Lindl.) Plantlet By Biostimune Extract Gotu Kola (Centella Asiatica L.) Treatment

Black orchid plantlets have a relatively slow growth at the acclimatization stage. The growth of black orchid plantlets can be increased by giving biostimulants. Biostimulants are bioactive compounds, and when they are applied, they can increase plant growth. This study aims to determine the effect of biostimulant Gotu kola extract (Centella Asiatica L.) on the growth of black orchid plantlets (Coelogyne Pandurata Lindl.) at the acclimatization stage. The research was conducted at the Biology Department's greenhouse from September until December 2020. The study used a completely randomized design with a factorial pattern. The first factor is the concentration of biostimulants consisting of 5 levels, e.g: 0 mg/L; 25 mg/L; 50 mg/L; 75 mg/L; 100 mg/L. The second factor is the application time which consists of 2 levels: once a week and once every two weeks. The results showed that the application of biostimulant Gotu kola extract had no significant effect on plantlet height, leaf length, leaf width, number of leaves, number of tillers, and number of plantlet roots of black orchid in the acclimatization stage.

Root-Associated Endophytic and Mycorrhizal Fungi from the Epiphytic Orchid Maxillaria acuminata in a Tropical Montane Forest in Southern Ecuador

In natural environments, it has been shown that orchids interact with multiple microorganisms including various species of fungi that colonize their tissues. The diversity of these fungi associated with orchid roots is still being described along with the ecological role they play when interacting with the orchids. In this study, we evaluated the richness and diversity of the endophytic and mycorrhizal fungi associated with the roots of Maxillaria acuminata, a common epiphytic orchid species from a tropical montane forest in southern Ecuador. We characterized the fungal communities by sequencing the ITS2 region of the nrDNA with Illumina MiSeq technology. In total, 843 fungal OTUs were uncovered using a 97% sequence similarity. The highest percentage of OTUs belonged to the Agaricomycetes class, Basidiomycota. Interestingly, the most frequent trophic guild from the analyzed OTUs was assigned as saprophytic. Also, some groups of orchid mycorrhizal-forming fungi were detected, including members within the families Ceratobasidicaceae, Serendipitaceae, Tulasnellaceae, and in the order Atractiellales. We discuss the potential influence of this diverse group of root-associated endophytic fungi on the development and survival of M. acuminata in the tropical forests of southern Ecuador.

Genome sequencing and evolutionary analysis of a new endophytic Trichoderma species isolated from orchid roots with reduced repertoire of protein-coding genes

Genome sequencing and evolutionary analysis of a new endophytic Trichoderma species isolated from orchid roots with reduced repertoire of protein-coding genes

Precipitation increased the proportion of non-mycorrhizal fungi in Plantathera chlorantha orchid roots

Orchids are endangered due to their extremely high ornamental and medicinal values, and their growth and development are closely related to root fungal communities. Therefore, the study of fungi in orchid roots helps in the protection and population restoration of orchids. This study compared the specificity and composition of the fungal community in the roots of the greater butterfly-orchid Platanthera chlorantha under three precipitation conditions (400–500 mm, L; 700–800 mm, M; and 1000–1100 mm, H). The results showed that non-mycorrhizal fungi accounted for >92% of the root fungal community of P. chlorantha. The proportion of non-mycorrhizal fungi Trichoderma in L (12.84%) and M (25.26%) conditions was significantly higher than that in H (2.57%), indicating that with an increase in precipitation, they play important roles in improving plant drought resistance and growth and development. The only mycorrhizal fungus Ceratobasidiaceae, which accounted for >1% of the total sequences, was significantly reduced under high precipitation habitats, indicating that it is more likely to survive in low precipitation habitats. Chao 1 and ACE index increased significantly with increased precipitation; however, there was no significant difference in Simpson and Shannon index, indicating that precipitation affects the structure of the root symbiotic fungal community of P. chlorantha, although the fungal community only revolves around some key species changes. This study provides a reference for the in-depth analysis of the relationship between fungal communities and environmental factors in orchid roots, and a theoretical basis for the protection and ecological restoration of orchid populations.

Fusarium–orchid interactions under greenhouse conditions

Orchids reveal a complexity of interactions with their microbial partners, particularly with mycorrhizal fungi. Orchid roots are also colonized by a number of associated endophytic fungi, whose activity and role is as yet insufficiently known. Here we studied the relations between two epiphytic orchids, Dendrobium moshatum and D. nobile, and several strains of the genus Fusarium – two pathogenic, F. fujikuroi (IMI58289) and F. proliferatum (NRRL 62905), and an orchid-associated, Fusarium proliferatum ET1. Recent reports indicate that F. proliferatum shows a high phenotypic variation in causing symptoms on one or different hosts. In this study, in contrast to the pathogenic species, an orchid-associated F. proliferatum ET1 strain showed its neutral endophytic lifestyle strategy towards the host-orchids. Despite an invasive and aggressive distribution of both phytopathogens, causing the root and leaf symptoms, the moderate colonization of F. proliferatum ET1 did not cause any negative effects on the adult plants during the experimental period. The quantitative characteristic of the fungal growth assessed by counting colony forming units confirmed the results of the bioassay, supporting the strain-specificity of the orchid-fungal interactions and a pattern of balanced relations with the non-mycorrhizal endophytic Fusarium isolate.

Multiple Fungi May Connect the Roots of an Orchid (Cypripedium reginae) and Ash (Fraxinus nigra) in Western Newfoundland.

Showy lady's slipper (Cypripedium reginae Walter, Orchidaceae) and black ash (Fraxinus nigra Marshall, Oleaceae) often co-occur in close proximity in fens in western Newfoundland, Canada. Metabarcoding of DNA extracted from root samples of both species following surface sterilization, and others without surface sterilization was used to determine if there were shared fungal endophytes in the roots of both species that could form a common mycorrhizal network between them. A wide variety of fungi were recovered from primers amplifying the nuclear ribosomal internal transcribed spacer region (ITS2). Sixty-six fungal sequences were shared by surface-sterilized roots of both orchid and ash, among them arbuscular mycorrhizal fungi (Claroideoglomus, Dominikia, Glomus and Rhizophagus), ectomycorrhizal fungi (Inocybe and Tomentella), the broad-host root endophyte Cadophora orchidicola, along with root pathogens (Dactylonectria, Ilyonectria, Pyricularia, and Xylomyces) and fungi of unknown function. There appear to be multiple fungi that could form a common mycorrhizal network between C. reginae and F. nigra, which might explain their frequent co-occurrence. Transfer of nutrients or carbon between the orchid and ash via one or more of the shared fungal endophytes remains to be demonstrated.

Widely targeted metabolic, physical and anatomical analyses reveal diverse defensive strategies for pseudobulbs and succulent roots of orchids with industrial value

Storage in pseudobulbs and succulent roots is vulnerable to attack from herbivores while play an important role in industrial utilization of orchids. However, we know little about the defensive strategies of pseudobulbs and succulent roots. Here, we characterized the possible physical and chemical defenses of pseudobulbs and succulent roots of five orchids with industrial value (Bletilla striata, Dendrobium chrysotoxum, Cymbidium tracyanum, C. sinense, and Acampe rigida) using X-ray micro-computerized tomography scanning and optical microscope observation as well as widely targeted metabolic profiling. We found that pseudobulbs and succulent roots of different orchid species combine different physical and chemical defensive strategies, and the relationship between defense and storage functions depend on species and age. Of the pseudobulbs of five species, C. tracyanum recruited the strongest defensive strategies, consisting of a thick epidermis, larger proportion of needle-like calcium oxalate crystals, and higher content of alkaloids and quinones. The pseudobulbs of C. sinense had a higher proportion of vascular bundle, and those B. striata had the strongest tissue biomechanical resistance. However, pseudobulbs of D. chrysotoxum were the most vulnerable to herbivores with relatively higher nutrient content and weaker defensive protection. For the succulent roots of five species, A. rigida had the strongest storage ability, and correspondingly the most chemical defensive components, while a thicker velamen and higher proportion of needle-like calcium oxalate crystals were found in the roots of C. tracyanum and C. sinense respectively. Our results suggest that diverse combinations of defensive strategies play a role protecting pseudobulbs and succulent roots of orchids from biotic stress. These findings contribute to the cultivation management of orchids with industrial value.

Integrative Study Supports the Role of Trehalose in Carbon Transfer From Fungi to Mycotrophic Orchid.

Orchids rely on mycorrhizal symbiosis, especially in the stage of mycoheterotrophic protocorms, which depend on carbon and energy supply from fungi. The transfer of carbon from fungi to orchids is well-documented, but the identity of compounds ensuring this transfer remains elusive. Some evidence has been obtained for the role of amino acids, but there is also vague and neglected evidence for the role of soluble carbohydrates, probably trehalose, which is an abundant fungal carbohydrate. We therefore focused on the possible role of trehalose in carbon and energy transfer. We investigated the common marsh orchid (Dactylorhiza majalis) and its symbiotic fungus Ceratobasidium sp. using a combination of cultivation approaches, high-performance liquid chromatography, application of a specific inhibitor of the enzyme trehalase, and histochemical localization of trehalase activity. We found that axenically grown orchid protocorms possess an efficient, trehalase-dependent, metabolic pathway for utilizing exogenous trehalose, which can be as good a source of carbon and energy as their major endogenous soluble carbohydrates. This is in contrast to non-orchid plants that cannot utilize trehalose to such an extent. In symbiotically grown protocorms and roots of adult orchids, trehalase activity was tightly colocalized with mycorrhizal structures indicating its pronounced role in the mycorrhizal interface. Inhibition of trehalase activity arrested the growth of both symbiotically grown protocorms and trehalose-supported axenic protocorms. Since trehalose constitutes only an inconsiderable part of the endogenous saccharide spectrum of orchids, degradation of fungal trehalose likely takes place in orchid mycorrhiza. Our results strongly support the neglected view of the fungal trehalose, or the glucose produced by its cleavage as compounds transported from fungi to orchids to ensure carbon and energy flow. Therefore, we suggest that not only amino acids, but also soluble carbohydrates are transported. We may propose that the soluble carbohydrates would be a better source of energy for plant metabolism than amino acids, which is partially supported by our finding of the essential role of trehalase.

Characterizing the Phytotoxic Effects of Hydrogen Peroxide Root Dips on Hybrid Phalaenopsis Orchid Plants

Hydrogen peroxide (H2O2) is a well-known oxidizing agent often used as a remedy by consumers to treat algae and root decay from presumed root disease on interior plants, as well as to encourage root growth and health. To characterize the phytotoxic effects and define the safe concentration threshold for H2O2 use on ‘Vivaldi’ hybrid phalaenopsis orchid (hybrid Phalaenopsis), root systems were dipped for 3 minutes in 0%, 3%, 6%, or 12% H2O2 one time and observed in greenhouse conditions for the following 27 days. Root systems of each plant were assessed over time for percent visible root damage; ratings of root health on a scale of 1 to 5 points, with 5 points indicating “very healthy”; and final fresh and dry weights. To determine when symptoms manifested above the root zone, foliage and flower damage was evaluated over time by assessing percent visible foliage damage, ratings of foliage health, percent foliar wilt, flower/bud count, and final foliage and flower fresh and dry weights. Over the evaluation period, the root health rating of the ‘Vivaldi’ hybrid phalaenopsis orchids treated with 12% H2O2 decreased from 5 to 1.13, whereas those treated with 3% H2O2 only decreased from 5 to 4.13. H2O2 concentrations of 6% and 12% damaged root health permanently, whereas the 3% H2O2 concentration only caused minor damage to overall root health. However, algae were not killed at the 3% rate. Neither foliage nor flowers were seriously affected during the 3 weeks after application, but foliage wilt did result in the 6% and 12% treatments by week 4. As H2O2 concentration increased, fresh weights decreased in roots and leaves. Although a single 3% H2O2 root dip did not result in severe symptoms of phytotoxicity, the treatment’s long-term plant health effects are unknown. Because the 3% H2O2 root dip caused minor plant health setbacks and failed to subdue algae populations in the root zone, consumers should be wary of using H2O2 to improve orchid (Orchidaceae) root health and should instead focus on altering care and watering practices.

Strong primer bias for Tulasnellaceae fungi in metabarcoding: Specific primers improve the characterization of the mycorrhizal communities of epiphytic orchids.

Primer bias toward Tulasnellaceae fungi during PCR is a known issue with metabarcoding analyses for the assessment of orchid mycorrhizal communities. However, this bias had not been evaluated for the fungal communities of epiphytic orchids, which account for 69% of all orchid species diversity. We compared the mycorrhizal communities detected using two primer pairs, a fungal universal primer pair (ITS86F/ITS4) and Tulasnella-specific primer pair (5.8STulngs/ITS4-Tul2), using a mock community of fungal isolates from epiphytic orchids and also environmental samples, including orchid roots and a tree bark tip from the host tree of an epiphytic orchid collected. The detected mycorrhizal communities differed widely depending on the primer pairs used. The fungal universal primer pair successfully identified Ceratobasidiaceae and Serendipitaceae fungi but did not reflect Tulasnellaceae diversity. Tulasnellaceae fungi were mainly detected using the Tulasnella-specific primer pair. These tendencies were observed in both the mock community and environmental samples. These results strongly suggest that the use of a Tulasnella-specific primer in combination with a fungal universal primer is essential for assessing the mycorrhizal communities of orchids through metabarcoding analysis, especially in epiphytic orchids. Our study contributes to further understanding of the diversity of mycorrhizal fungi in orchids.

Root Morphology, Anatomy, and Mycorrhiza of Peristylus goodyeroides (D.Don) Lindl. (Orchidaceae) in Different Life Stages: Ecological Significance and Implication for Conservation

Orchid roots have vital functions for water absorption, nutrient uptake, a place of symbiosis with mycorrhizal fungi, adaptation, and survival. The aim of the present study was to investigate root traits in terms of root morphological, anatomical, and mycorrhizal features of a terrestrial orchid, Peristylus goodyeroides in relation to an ecological significance of root traits in survival of seedlings, juveniles, and adults of the orchid. Results showed that some morphological characters (root length and depth), anatomical features (cortical cell size, xylem number and diameter), and mycorrhizal features (peloton size and number) were significantly different between seedlings, juveniles, and adults. In relation to root functional traits, lowest root length, depth, xylem number and diameter, peloton size and number in seedlings can be associated with low capacity in water and nutrient acquisition that might explain low survival of seedlings relative to juveniles and adults. Present study has implication for orchid conservation suggesting high attention in low survival rate of seedlings related to specificity in some of their morphological, anatomical, and mycorrhizal features which can be associated with low capacity in water and nutrient acquisition. It is vital to ensure water availability for seedlings, particularly, during dry seasons to decrease high mortality of seedlings as such high mortality can have adverse impacts on long-term survival of the orchid population.

Induction of Rhizoctonia resistance to odontoglossum ringspot virus (ORSV) infection on orchid leaf organ viability

Orchid plants are in great demand by the public as ornamental plants that have economic value and the beauty of attractive flower shapes and colors, especially Phalaenopsis and Dendrobium. Related to this, conservation efforts are needed through cultivation. However, these efforts are often hampered by viral infections. One of the viruses that trigger inhibition of orchid cultivation that often appears is ORSV. Control efforts that are relatively safe and efficient can utilize mycorrhizae in orchids which play a role in increasing the absorption of plant nutrients. The use of Phalaenopsis and Dendrobium with the induction of Rhizoctonia sp. against ORSV is a very important alternative biofertilizer and biocontrol agent. The objectives of this study were 1) to determine the effectiveness of orchids induced by Rhizoctonia resistance, 2) to determine the viability of orchid leaf organs to ORSV infection, 3) to determine the viability of orchid root organs resulting from Rhizoctonia resistance to ORSV infection. This study was conducted in January 2021 – March 2021 at the Botanical 2 Laboratory, Department of Biology, Faculty of Mathematics and Natural Sciences, University of Lampung. This study employed a completely randomized factorial with 6 treatments and 4 replications. The variable observed in this study was the effectiveness of mycorrhizae, leaf and root length, number of leaves and roots, and leaf width. The data obtained were homogenized using Levene's test and then analyzed by ANOVA and Tukey's further test at the 5% level. The results showed that the effectiveness of mycorrhizae occurred on the 3rd day of incubation. In leaf organs, Phalaenopsis amabilis showed an increased response and Dendrobium discolour showed a decreased response in leaf length, width, and number. Meanwhile, in the root organ, Dendrobium discolour showed an increased response and Phalaenopsis amabilis showed a decreased response in root length and number of roots.

Getting a Grip on the Adhesion Mechanism of Epiphytic Orchids – Evidence From Histology and Cryo-Scanning Electron Microscopy

Plants and animals evolve different attachment structures and strategies for reversible or permanent adhesion to different substrate types. For vascular epiphytes, having the ability to permanently attach to their host plants is essential for establishment and survival. Unlike mistletoe roots, roots of vascular epiphytes do not penetrate the host tissues but instead achieve attachment by growing in close contact to the surface of the substrate. However, the fundamental understanding of the attachment functions of epiphytic roots remains scarce, where majority of studies focused on the general root morphology, their functional properties and the descriptions of associated microbial endophytes. To date, research on attachment strategies in plants is almost entirely limited to climbers. Therefore, this study aims to fill the knowledge gap and elucidate the attachment functions of roots of epiphytic orchids. With the use of histology and high-resolution cryo-scanning electron microscopy (cryo-SEM) technique with freeze fracturing, the intimate root-bark substrate interface of epiphytic orchid Epidendrum nocturnum Jacq was investigated. Results showed a flattened underside of the root upon contact with the substrate surface, and the velamen layer appeared to behave like a soft foam, closely following the contours of the substrate. Root hairs emerged from the outermost velamen layer and entered into the crevices in the substrate, whenever possible. A layer of amorphous substance (glue-like substance) was observed on the surface of the root hairs. Combining the observations from this study and knowledge from previous studies, we hypothesised that epiphytic orchid roots produced a layer of glue-like substance to adhere the root to the substrate. Then root hairs are produced and enter into the voids and crevices of the substrate. This further generates a mechanical interlocking mechanism between root and substrate, thus reinforcing the attachment of the root (and hence the whole plant) to its substrate.

In vitro culture of Dendrobium lineale Rolfe orchid for plant breeding and propagation

D.lineale is included in the CITES appendix II due to D. lineale has great potential as a cut flower and the parent of hybrid orchids. In vitro culture can be used for mass propagation of orchids for commercial breeding as well as conservation. Basic culture medium with the addition of organic substances can increase the growth of plantlets. The objective of this research was to determine the best condition for in vitro culture of D.lineale orchids for producing a mass number of plantlets. Methods used include planting orchid seedlings in various variations of culture media, plantlet subcultures, observation of the anatomy of leaves and roots, as well as the measurement of chlorophyll content. This research uses ‘pisang raja’ as organic material in the culture medium. The highest chlorophyll content in the leaves was 1.58 mg/g, while the highest chlorophyll content in the roots was 0.34 mg/g. Both were found in medium NP+100 g/L bananas in light conditions (1317 lux). The anatomical structure of the leaves shows that the mesophyll is thicker in plants placed under lighting 1317 lux because it shows good effectiveness in photosynthesis. The anatomy of the orchid roots showed differences in diameter in each treatment because the addition of bananas to the medium stimulated rapid and abundant root formation, but the size was smaller. Based on these results, it can be concluded that the addition of 100 gr/L bananas as organic substances in in vitro medium culture increases the growth rate of D. lineale orchids, which will be beneficial for conservation efforts.