An effective nutrient medium for asymbiotic seed germination and large-scale in vitro regeneration of Dendrobium hookerianum, a threatened orchid of northeast India

Submergence inhibits photosynthesis by terrestrial wetland plants, but less so in species that possess leaf gas films when submerged. Floodwaters are often supersaturated with dissolved CO2 enabling photosynthesis by submerged terrestrial plants, although rates remain well-below those in air. This important adaptation that enhances survival in submerged conditions is reviewed

SOME TECHNIQUES IN MICROPROPAGATION AND BREEDING OF Paphiopedilum spp.

Paphiopedilum orchids are one of the most popular and rare orchid genera sold and exhibited as pot plants and cut flowers. Their wild populations are under the threat of extinction as a result of over-collection and loss of suitable habitats. Reduction in their commercial value through large-scale propagation in vitro is a preferable option to reduce pressure from illegal collection, to attempt at meeting commercial needs and to re-establish these threatened orchid species back into the wild. Although they are commercially propagated via seed germination in vitro, Paphiopedilum are considered to be difficult to propagate in vitro, especially by plant regeneration from tissue culture. This paper aims to provide the most important techniques on Paphiopedilum propagation mainly including plant, cell, tissue and organ culture techniques applied to in vitro propagation of Paphiopedilum and to emphasize the importance of further improving tissue culture protocols from ex vitro-derived explants of mature plants

Complete Chloroplast Genome of Paphiopedilum delenatii and Phylogenetic Relationships among Orchidaceae

Paphiopedilum delenatii is a native orchid of Vietnam with highly attractive floral traits. Unfortunately, it is now listed as a critically endangered species with a few hundred individuals remaining in nature. In this study, we performed next-generation sequencing of P. delenatii and assembled its complete chloroplast genome. The whole chloroplast genome of P. delenatii was 160,955 bp in size, 35.6% of which was GC content, and exhibited typical quadripartite structure of plastid genomes with four distinct regions, including the large and small single-copy regions and a pair of inverted repeat regions. There were, in total, 130 genes annotated in the genome: 77 coding genes, 39 tRNA genes, 8 rRNA genes, and 6 pseudogenes. The loss of ndh genes and variation in inverted repeat (IR) boundaries as well as data of simple sequence repeats (SSRs) and divergent hotspots provided useful information for identification applications and phylogenetic studies of Paphiopedilum species. Whole chloroplast genomes could be used as an effective super barcode for species identification or for developing other identification markers, which subsequently serves the conservation of Paphiopedilum species

EFFECT OF METAL NANOPARTICLES ON THE GROWTH OF NGOC LINH GINSENG (PANAX VIETNAMENSIS) LATERAL ROOTS CULTURED IN VITRO

Ngoc Linh ginseng plays important in pharmaceutical industry because its triterpenoid saponin drugs could improve health and treat many diseases. Metal nanoparticles revealed completely new properties based on specific characteristics (size, distribution and morphology) compared to metal ions or salts, especially, their potential applications in plant tissue culture. Effects of metal nanoparticles (0.5–2.5 mg/L nZnO, 1–3 mg/L nAg, and 1–3 mg/L nCu) in free-hormone-MS medium were studied on the Ngoc Linh ginseng root culture. Results showed that nAg and nCu increased positive effects on the lateral root formation and growth at different concentrations. Except for, the root abnormal anatomical morphology revealed that cell layers of xylem, endodermis and epidermis thicken and darken, or vascular bundle expand, or some black points appeared in root caps and dorsal bundles. The optimal metal nanoparticle for the root growth is nCu; and the highest growth indexes were obtained at 1.5 mg/L nCu with 99.3% lateral root formation). The ginseng root grew at 2.5 mg/L nAg better, but more abnormalities. The inhibition growth and negative impacts on the ginseng root were recorded in the medium containing nZnO (0.5–2.5 mg/L) and the highest metal nanoparticle concentration (above 2.5 mg/L nCu and nAg).Panax vietnamensis (Ngoc Linh ginseng) plays critical roles in pharmaceutical industry because triterpenoid saponins from its roots produce medicine for improving health and treating many diseases. Metal nanoparticles reveal completely new or improved properties based on specific characteristics such as size, distribution and morphology compare to metal ion or salt; and their potential for in vitro plant cultures. Present study investigated the effects of metal nanoparticles including nZnO (0.5-2.5 mg/l), nAg (1-3 mg/l), and nCu (1-3 mg/l) supplemented in free-hormone-MS medium to in vitro Panax vietnamensis lateral root growth. Our results showed that metal nanoparticles have the positive effect on the growth of in vitro P. vietnamensis lateral roots with nAg, nCu, and nZnO. At different concentrations, in vitro P. vietnamensis lateral root growth also has various effects on the growth of lateral roots. In supplemented metal nanoparticle treatments, nCu is the most optimum for in vitro P. vietnamensis lateral root growth; the highest increase was obtained at 1.5 mg/l nCu treatment (99.3% lateral root formation and all root growth indexes are the highest). Besides, 2.5 mg/l nAg is also significantly noticed in ginseng root growth. However, the negative impact on the growth of the in vitro P. vietnamensis lateral roots showed when culture medium contained the highest concentration; such as the root growing inhibition of nCu and nAg above 2.5 mg/l. Especially, this decrease was higher with the application of nZnO0.5-2.5 mg/l (decrease the lateral root number) and 2.5 mg/l (decrease percent of lateral root formation)

Sự hình thành phôi vô tính từ mô sẹo có nguồn gốc từ lớp mỏng tế bào lá cắt ngang ở sâm Việt Nam (Panax vietnamensis Ha et Grushv.)

No report on plant regeneration via somatic embryogenesis of P. vietnamensis has been previously published. In the present study, somatic embryogenesis via callus formation from cultures of leaf transverse thin cell layers (tTCLs) of Vietnamese ginseng (Panax vietnamensis Ha et Grushv.) was investigated. α-naphthaleneacetic acid (NAA), 2,4-dichlorophenoxyacetic acid (2,4-D), 6-benzylaminopurine (BA) and thidiazuron (TDZ) were added separately and in combination into the culture media. Explant necrosis or low callogenesis rates were observed when 1-mm wide leaf tTCLs were cultured on media with TDZ, BA, 2,4-D or NAA. On the other hand, calli were successfully induced from the tTCL explants cultured on medium supplemented with either 2,4-D and BA or 2,4-D and TDZ. Callogenesis was observed under both light and dark conditions. The highest callogenesis rate (100%) was obtained on Murashige and Skoog (MS) basal medium supplemented with 1.0 mg l-1 2,4-D in combination with 0.1 mg l-1 TDZ in darkness after eight weeks of culture. White calli were cut into small pieces (1.0 x 1.0 cm dimension) and placed on MS media containing 1.0 mg l-1 2,4-D, 0.5 mg l-1 NAA and TDZ at various concentrations (0.01; 0.1; 0.2; and 0.5 mg l-1), and the best callus proliferation was recorded on medium containing 1.0 mg l-1 2,4-D and 0.2 mg l-1 TDZ. Somatic embryogenesis, with a success rate of 53.3% and 35 embryos per explant, was achieved when calli were subcultured onto MS medium supplemented with 1.0 mg l-1 2,4-D, 0.5 mg l-1 NAA and 0.2 mg l-1 TDZ.Đến nay, chưa có báo cáo nào công bố về sự tái sinh cây thông qua quá trình phát sinh phôi vô tính ở sâm Việt Nam. Trong nghiên cứu này, khả năng phát sinh phôi vô tính gián tiếp qua sự hình thành mô sẹo từ việc nuôi cấy mẫu lớp mỏng tế bào cắt ngang của lá (tTCL) ở sâm Việt Nam (Panax vietnamensis Ha et Grushv.) đã được tiến hành nghiên cứu. Các chất điều hòa sinh trưởng hực vật α-naphthaleneacetic acid (NAA), 2,4-dichlorophenoxyacetic acid (2,4-D), 6-benzylaminopurine (BA) và thidiazuron (TDZ) đã được bổ sung ở dạng riêng lẻ hoặc kết hợp vào môi trường nuôi cấy. Mẫu cấy bị hoại tử hoặc tỷ lệ tạo mô sẹo thấp đã được ghi nhận khi các mẫu tTCL với độ rộng 1 mm được nuôi cấy trên môi trường có bổ sung chỉ một chất điều hòa sinh trưởng thực vật. Trong khi, việc cảm ứng hình thành mô sẹo thành công từ các mẫu được nuôi cấy trên môi trường có bổ sung 2,4-D và BA hoặc 2,4-D kết hợp với TDZ. Sự hình thành mô sẹo đã được ghi nhận cả dưới điều kiện chiếu sáng và trong điều kiện tối. Tỷ lệ hình thành mô sẹo cao nhất (100%) thu được trên môi trường Murashige và Skoog (MS) có bổ sung 1,0 mg l-1 2,4-D kết hợp với 0,1 mg l-1 TDZ trong điều kiện tối sau 8 tuần. Mô sẹo màu trắng được cắt thành những mẫu nhỏ (1,0 x 1,0 cm) và cấy lên môi trường MS có bổ sung 1,0 mg l-1 2,4-D, 0,5 mg l-1 NAA và TDZ ở các nồng độ khác nhau (0,01; 0,1; 0,2 và 0,5 mg l-1) và sự tăng sinh mô sẹo tốt nhất đã được ghi nhận trên môi trường có bổ sung 1,0 mg l-1 2,4-D và 0,2 mg l-1 TDZ. Sự phát sinh phôi vô tính thành công với tỷ lệ tạo phôi 53,3% và 35 phôi/mẫu cấy đã thu được khi mô sẹo được nuôi cấy trên môi trường MS có bổ sung 1,0 mg l-1 2,4-D, 0,5 mg l-1 NAA and 0,2 mg l-1 TDZ

CNT-molecule-CNT (1D-0D-1D) van der Waals integration ferroelectric memory with 1-nm(2) junction area

© 2022 Springer Nature Limited. The device's integration of molecular electronics is limited regarding the large-scale fabrication of gap electrodes on a molecular scale. The van der Waals integration (vdWI) of a vertically aligned molecular layer (0D) with 2D or 3D electrodes indicates the possibility of device's integration; however, the active junction area of 0D-2D and 0D-3D vdWIs remains at a microscale size. Here, we introduce the robust fabrication of a vertical 1D-0D-1D vdWI device with the ultra-small junction area of 1 nm(2) achieved by cross-stacking top carbon nanotubes (CNTs) on molecularly assembled bottom CNTs. 1D-0D-1D vdWI memories are demonstrated through ferroelectric switching of azobenzene molecules owing to the cis-trans transformation combined with the permanent dipole moment of the end-tail -CF3 group. In this work, our 1D-0D-1D vdWI memory exhibits a retention performance above 2000 s, over 300 cycles with an on/off ratio of approximately 10(5) and record current density (3.4 x 10(8) A/cm(2)), which is 100 times higher than previous study through the smallest junction area achieved in a vdWI. The simple stacking of aligned CNTs (4 x 4) allows integration of memory arrays (16 junctions) with high device operational yield (100%), offering integration guidelines for future molecular electronics. The van der Waals integration of molecular layer (0D) with 2D or 3D electrodes is limited at microscale junction. Here, the authors introduce 1D-0D-1D vdWI memory with 1 nm(2) junction achieved by cross-stacking t-CNT on molecularly assembled b-CNT.11Nsciescopu

Synthesis of a Selectively Nb-Doped WS2-MoS2 Lateral Heterostructure for a High-Detectivity PN Photodiode

Copyright © 2022 American Chemical Society. In this study, selective Nb doping (P-type) at the WS2 layer in a WS2-MoS2 lateral heterostructure via a chemical vapor deposition (CVD) method using a solution-phase precursor containing W, Mo, and Nb atoms is proposed. The different chemical activity reactivity (MoO3 > WO3 > Nb2O5) enable the separation of the growth temperature of intrinsic MoS2 to 700 degrees C (first grown inner layer) and Nb-doped WS2 to 800 degrees C (second grown outer layer). By controlling the Nb/(W+Nb) molar ratio in the solution precursor, the hole carrier density in the p-type WS2 layer is selectively controlled from approximately 1.87 x 10(7)/cm(2) at 1.5 at.% Nb to approximately 1.16 x 10(13)/cm(2) at 8.1 at.% Nb, while the electron carrier density in n-type MoS2 shows negligible change with variation of the Nb molar ratio. As a result, the electrical behavior of the WS2-MoS2 heterostructure transforms from the N-N junction (0 at.% Nb) to the P-N junction (4.5 at.% Nb) and the P-N tunnel junction (8.1 at.% Nb). The band-to -band tunneling at the P-N tunnel junction (8.1 at.% Nb) is eliminated by applying negative gate bias, resulting in a maximum rectification ratio (10(5)) and a minimum channel resistance (10(8) omega). With this optimized photodiode (8.1 at.% Nb at V-g = -30 V), an I-photo/I-dark ratio of 6000 and a detectivity of 1.1 x 10(14)Jones are achieved, which are approximately 20 and 3 times higher, respectively, than the previously reported highest values for CVD-grown transition-metal dichalcogenide P-N junctions.11Nsciescopu

Design and Fabrication of Side channel Photonic Crystal Fiber

International audienc

Tunable Negative Differential Resistance in van der Waals Heterostructures at Room Temperature by Tailoring the Interface

© 2019 American Chemical Society.Vertically stacked two-dimensional van der Waals (vdW) heterostructures, used to obtain homogeneity and band steepness at interfaces, exhibit promising performance for band-to-band tunneling (BTBT) devices. Esaki tunnel diodes based on vdW heterostructures, however, yield poor current density and peak-to-valley ratio, inferior to those of three-dimensional materials. Here, we report the negative differential resistance (NDR) behavior in a WSe2/SnSe2 heterostructure system at room temperature and demonstrate that heterointerface control is one of the keys to achieving high device performance by constructing WSe2/SnSe2 heterostructures in inert gas environments. While devices fabricated in ambient conditions show poor device performance due to the observed oxidation layer at the interface, devices fabricated in inert gas exhibit extremely high peak current density up to 1460 mA/mm2, 3-4 orders of magnitude higher than reported vdW heterostructure-based tunnel diodes, with a peak-to-valley ratio of more than 4 at room temperature. Besides, Pd/WSe2 contact in our device possesses a much higher Schottky barrier than previously reported Cr/WSe2 contact in the WSe2/SnSe2 device, which suppresses the thermionic emission current to less than the BTBT current level, enabling the observation of NDR at room temperature. Diode behavior can be further modulated by controlling the electrostatic doping and the tunneling barrier as well11sciescopu

Bioeconomics of cobia, Rachycentron canadum, culture in Vietnam

This article presents an analysis of the profitability and intensity of cobia culture by small-scale farmers in Vietnam, especially focusing on current feeding practices and perceptions regarding adoption of manufactured diets. Bioeconomic modelling is used so the interactions between biological and economic processes can be analyzed. Overall, it is found that cobia farming is moderately to highly profitable when compared to other aquaculture species in Vietnam. Culture practices and the level of intensity of cobia farming differ significantly across Vietnam. Initial stocking density, total number of fish stocked, number and size of cages, and quantity of feed used are all higher in southern Vietnam than the north. The higher level of intensification in the south leads to significantly higher total costs, productivity and profitability. The dominant cost source is feed, which is predominantly low-value fish. To capture the environmental and potential economic benefits of adopting pelleted diets, then negative farmer perceptions regarding relatively slow growth rates, and lack of availability compared with low-value fish need to be overcome