In vitro seed germination and plantlet regeneration of Vanilla siamensis: an endemic species in Thailand

This study reports the in vitro germination of self-pollinated pod of Vanilla siamensis, native to Thailand. The aim of the present work is to determine the effect of culture media and plant growth regulators on seed germination and plantlet regeneration. The vanilla seeds were asymbiotically germinated on different culture media under aseptic conditions. The results showed that, New Dogashima medium (NDM) supplemented with 2% (w/v) sucrose, 15% (v/v) coconut water (CW) and 0.7% (w/v) agar gave the highest levels of seed germination at 10.1%. The fastest and highest percentage seed germination was achieved using NDM supplemented with 2 mg/l gibberellic acid (GA3). Seeds on this culture medium germinated within 7–8 weeks in comparison with 10–11 weeks on culture medium without plant growth regulators. Protocorms were transferred to different culture media with various concentrations of 6- benzyladenine (BA) to assess the protocorm development. The results revealed that 1⁄2 Murashige and Skoog (1⁄2 MS) medium gave the higher result in survival rate of protocorm than NDM. 1⁄2 MS medium with 0.5 mg/l BA was suitable for shoot formation. Plantlet development was completed after subculturing on 1⁄2 MS medium supplemented with 0.5 mg/l α-naphthaleneacetic acid (NAA) for 8 weeks and successfully acclimatized at 91.7%. The protocol outline here can be used for mass propagation of this endangered species and used as a guideline for improvement of V. siamensis and its in vitro conservation

Electric field distribution in porous piezoelectric materials during polarization

High piezoelectric coupling coefficients enable the harvesting of more energy or increase the sensitivity of sensors which work using the principle of piezoelectricity. These coefficients depend on the material properties, but the manufacturing process can have a significant impact on the resulting overall coefficients. During the manufacturing process, one of the main steps is the process of polarization where a poling electric field aligns the ferroelectric domains in a similar direction in order to create a transversely isotropic material able to generate electric fields or deformations. The degree of polarization depends on multiple factors and it can strongly influence the final piezoelectric coefficients. In this paper, a study on the electric field distribution on the sensitivity of the main piezoelectric and dielectric coefficients to the polarization process is performed, focusing on porous piezoelectric materials. Different inclusion geometries are considered, namely spherical, ellipsoidal and spheres with cracks. The electric field distribution at the micro scale within a representative volume element is modelled to determine the material polarization level using the finite element method. The results show that the electric field distribution is highly dependent on the inclusion geometries and cracks and it has a noticeable impact on the equivalent piezoelectric coefficients. These results are compared with experimental measurements from published literature. Good agreement is found between the ellipsoidal model and the experimental data

Impact of ecological factors on the distribution of Vanilla siamensis (Orchidaceae: Vanilloideae) in tropical forest at Khao Soi Dao Wildlife Sanctuary, Chantaburi, Thailand

Some species of the pantropical orchid genus Vanilla are widely used in a variety of industries, including food, pharmaceuticals, cosmetics, tobacco and traditional crafts. Vanilla siamensis Rolfe ex Downie is a leafy vine endemic to Thailand. Ecolog- ical factors affecting the distribution of V. siamensis are still unknown. This study aims to examine the distribution of V. siamensis in natural conditions as well as to investigate the impact of environmental factors on its distribution in forest ecosystems. In order to achieve the proposed objectives, a study was conducted in a tropical moist forest at Khao Soi Dao Wildlife Sanctuary. The plant community and environmental factors where V. siamensis occurs were assessed in two study sites. At each site, two plots (10 m×50 m) were set up near waterfalls (NWA) and in adjacent forest areas (AFA). A total of 66 species of woody plants were recorded in the study plots. Higher values for importance value index (IV) were found for Pterygota alata (Roxb.) R.BR., Diospyros de- fectrix H.R. Fletcher, Strombosia ceylanica Gardner, Alchornea rugosa (Lour.) Mull. Arg., and Diospyros transitoria Bakh. The highest number of tree species, number of individu- als, Shannon diversity index and evenness were found at the NWA compared to the AFA. A total of 19 woody plant species act as support trees of V. siamensis in the plant families Malvaceae, Annonaceae and Achariaceae. The results showed that V. siamensis might pos- sible well adapted in the NWA study zone which contained a higher level of soil moisture content compared to the AFA. All results revealed that the distribution of V. siamensis in the study areas could be impacted by tree hosts. All tree host species have a larger diameter at breast height and thicker and softer bark when compared with non-tree hosts