Symbiotic seed germination of an endangered epiphytic slipper orchid, Paphiopedilum villosum (Lindl.) Stein. from Thailand

Published by Elsevier B.V. Paphiopedilum villosum (Lindl.) Stein is a native epiphytic slipper orchid in Thailand. This species is now being threatened and endangered. Propagation of this species is essential for conservation and reintroduction purposes. In this study, the propagation of P. villosum was achieved through the in vitro asymbiotic and symbiotic seed germination. Seeds of P. villosum sown on asymbiotic media, Murashige and Skoog (MS), Vacin and Went (VW) and Thomale GD (TH), did not germinate within 16. weeks. Seven different fungal strains were isolated from roots of this orchid species. The germination rate index (GRI) and the development rate index (DRI) of P. villosum seeds in treatments inoculated with fungal isolates PVCP01, PVCP05, and PVCP06 was significantly higher than uninoculated control treatments. Fungal isolate PVCP01 significantly increased the GRI and DRI of every stage of protocorm development, whereas fungal isolates PVCP05 and PVCP06 were only able to promote seed germination and protocorm development to stage 2. As for the wild orchid species, P. villosum, a compatible fungus is therefore required for promoting seed germination and protocorm development. Based on analysis of morphological characters and sequences of the nuclear ribosomal transcribed spacer (ITS), fungal isolates PVCP01, PVCP 05, and PVCP06 were identified as Tulasnella sp., Ceratobasidium sp., and Flavodon sp., respectively. The information obtained from this study will be used to propagate other threatened Thai orchids for conservation and reintroduction programs

Using in situ seed baiting technique to isolate and identify endophytic and mycorrhizal fungi from seeds of a threatened epiphytic orchid, Dendrobium friedericksianum Rchb.f. (Orchidaceae)

© 2016 Kasetsart University. All orchids require association with mycorrhizal fungi for seed germination and development under natural conditions but their identification and feasibility are not known. The in situ seed baiting germination was examined of Dendrobium friedericksianum Rchb.f., a native threatened epiphytic orchid species, to detect fungi that promote germination. It was found that seed germination percentages were lowered by 0.1%, with a total of seven protocorms formed. Six endophytic fungi were isolated from seven protocorms in seed packets. Three binucleate Rhizoctonia-like fungal isolates which formed a teleomorphic state were morphologically identified as Tulasnella violea, Epulorhiza repen (anamorph Tulasnella) and Trichosporiella multisporum. The species of Beauvaria and Fusarium which are endophyte fungi were also isolated and may play an important role for plant growth and survival of D. friedericksianum. The results in this study suggested that in situ seed baiting is beneficial for screening compatible mycorrhizal fungi to promote the growth and propagation of epiphytic orchids

High Crystalline Dithienosilole-Cored Small Molecule Semiconductor for Ambipolar Transistor and Nonvolatile Memory

We characterized the electrical properties of a field-effect transistor (FET) and a nonvolatile memory device based on a solution-processable low bandgap small molecule, Si1TDPP-EE-C6. The small molecule consisted of electron-rich thiophene-dithienosilole-thiophene (Si1T) units and electron-deficient diketopyrrolopyrrole (DPP) units. The as-spun Si1TDPP-EE-C6 FET device exhibited ambipolar transport properties with a hole mobility of 7.3 X 10(-5) cm(2)/(V s) and an electron mobility of 1.6 X 10(-5) cm(2) /(V s). Thermal annealing at 110 degrees C led to a significant increase in carrier mobility, with hole and electron mobilities of 3.7 X 10(-3) and 5.1 X 10(-4) cm(2)/(Vs), respectively. This improvement is strongly correlated with the increased film crystallinity and reduced pi-pi intermolecular stacking distance upon thermal annealing, revealed by grazing incidence X-ray diffraction (GIXD) and atomic force microscopy (AFM) measurements. In addition, nonvolatile memory devices based on Si1TDPP-EE-C6 were successfully fabricated by incorporating Au nanoparticles (AuNPs) as charge trapping sites at the interface between the silicon oxide (SiO2) and cross-linked poly(4-vinylphenol) (cPVP) dielectrics. The device exhibited reliable nonvolatile memory characteristics, including a wide memory window of 98 V, a high on/off-current ratio of 1 X 10(3), and good electrical reliability. Overall, we demonstrate that donor-acceptor-type small molecules are a potentially important class of materials for ambipolar FETs and nonvolatile memory applications

Nanoscopic Management of Molecular Packing and Orientation of Small Molecules by a Combination of Linear and Branched Alkyl Side Chains

We synthesized a series of acceptor donor acceptor-type small molecules (SIDPP-EE, SIDPP-EO, SIDPP-OE, and SIDPP-OO) consisting of a dithienosilole (SI) electron-donating moiety and two diketopyrrolopyrrole (DPP) electron-withdrawing moieties each bearing linear n-octyl (O) and/or branched 2-ethylhoryl (E) alkyl side chains. X-ray diffraction patterns revealed that SIDPP-EE and SIDPP-EO films were highly crystalline with pronounced edge-on orientation, whereas SIDPP-OE and SIDPP-OO films were less crystalline with a radial distribution of molecular orientations. Near-edge X-ray absorption fine structure spectroscopy disclosed an edge-on orientation with a molecular backbone tilt angle of similar to 22 degrees for both SIDPP-EE and SIDPP-EO. Our analysis of the molecular packing and orientation indicated that the shorter 2-ethylhexyl groups on the SI core promote tight pi-pi stacking of the molecular backbone, whereas n-octyl groups on the SI core hinder close pi-pi stacking to some degree. Conversely, the longer linear n-octyl groups on the DPP arms facilitate close intermolecular packing via octyl octyl interdigitation. Quantum mechanics/molecular mechanics molecular dynamics simulations determined the optimal three-dimensional positions of the flexible alkyl side chains of the SI and DPP units, which elucidates the structural cause of the molecular packing and orientation explicitly. The alkyl-chain-dependent molecular stacking significantly affected the electrical properties of the molecular films. The edge-on oriented molecules showed high hole mobilities in organic field-effect transistors, while the radially oriented molecules exhibited high photovoltaic properties in organic photovoltaic cells. These results demonstrate that appropriate positioning of alkyl side chains can modulate crystallinity and molecular orientation in SIDPP films, which ultimately have a profound impact on carrier transport and photovoltaic performance