Soil Mineral Composition and Salinity Are the Main Factors Regulating the Bacterial Community Associated with the Roots of Coastal Sand Dune Halophytes.

Soil salinity and mineral deficiency are major problems in agriculture. Many studies have reported that plant-associated microbiota, particularly rhizosphere and root microbiota, play a crucial role in tolerance against salinity and mineral deficiency. Nevertheless, there are still many unknown parts of plant-microbe interaction, especially regarding their role in halophyte adaptation to coastal ecosystems. Here, we report the bacterial community associated with the roots of coastal sand dune halophytes Spinifex littoreus and Calotropis gigantea, and the soil properties that affect their composition. Strong correlations were observed between root bacterial diversity and soil mineral composition, especially with soil Calcium (Ca), Titanium (Ti), Cuprum (Cu), and Zinc (Zn) content. Soil Ti and Zn content showed a positive correlation with bacterial diversity, while soil Ca and Cu had a negative effect on bacterial diversity. A strong correlation was also found between the abundance of several bacterial species with soil salinity and mineral content, suggesting that some bacteria are responsive to changes in soil salinity and mineral content. Some of the identified bacteria, such as Bacillus idriensis and Kibdelosporangium aridum, are known to have growth-promoting effects on plants. Together, the findings of this work provided valuable information regarding bacterial communities associated with the roots of sand dune halophytes and their interactions with soil properties. Furthermore, we also identified several bacterial species that might be involved in tolerance against stresses. Further work will be focused on isolation and transplantation of these potential microbes, to validate their role in plant tolerance against stresses, not only in their native hosts but also in crops.

Seed Morphometry of Native Indonesian Orchids in the Genus Dendrobium.

In this study, seeds of 10 species of epiphytic orchids were examined using light and scanning electron microscope. Quantitative and qualitative characters were analyzed. All the presently investigated seeds showed are transparent with visible embryo and remarkable embryo color variations (such as pale yellow, light yellow, shiny yellow to yellow, orange, and white). The species showed two groups in seed shape (fusiform and filiform), prolate and oval-shaped embryo, positioned at the center of the long axis and near apical pole. Embryo in prolate shaped and near apical pole position was only in D. antennatum. Based on our investigation, there are variations in seed and embryo volume as well as percentage air space in different taxa of orchids. The highest air space percentages were found in D. leporinum. According to the ornamentation of testa cells, 3 types of seeds were discovered in this genus. Additionally, the clear variation in the testa ornamentation pattern includes the species of D. leporinum, where the testa cells were in the medial regular rectangles, but in the apical and basal pole they are polygonal and irregularly oriented; the testa cells of D. antennatum are polygonal and irregularly oriented and those of D. purpureum are longitudinally oriented with regular rectangles.

In Vitro Seed Germination and Seedling Development of a Rare Indonesian Native Orchid Phalaenopsis amboinensis J.J.Sm.

Phalaenopsis amboinensis, an epiphytic orchid, has a great potential for commercial exploitation in the cut-flower industry. It is difficult to propagate vegetatively as it naturally grows slowly. Therefore, there is a need to improve the propagation methods to avoid endangering its natural populations. The objective of this study was to identify the best medium and organic supplements for seed germination and plantlets development of P. amboinensis. Seeds from 4-month-old hand-pollinated orchids were sown on different strengths of MS and VW culture media: Murashige and Skoog (MS), 1/2 MS, Vacin and Went (VW), and 1/2 VW. Optimum seed germination, i.e., 90.7%, was achieved on VW medium. VW medium was suitable for seedling formation and allowed 51.4% of seedling development from protocorm within 10 weeks of culture. When 15% (v/v) coconut water was added together with banana homogenate (10 g·L-1) to the VW medium, the plantlets grew to the highest length and had the highest dry weight (62.1 mm and 15.5 g, respectively). The roots and leaves of the plantlets grew vigorously in this medium. Plants regenerated via in vitro seed germination processes were successfully acclimatized in greenhouse conditions, and the survival rate was more than 85%.

Data of root anatomical responses to periodic waterlogging stress of tobacco (Nicotiana tabacum) varieties.

The data of root anatomical structure and the formation of aerenchyma tissues of five varieties of tobacco under waterlogging stress were obtained by modified paraffin method. Each tobacco varieties performed distinct anatomical adaptation response, including changes of cortical tissue, stele diameter, xylem diameter and the formation of aerenchyma under periodic waterlogging stress.

Agrobacterium tumefaciens-mediated transformation of Dendrobium lasianthera J.J.Sm: An important medicinal orchid.

A protocol for genetic transformation mediated by Agrobacterium tumefaciens and production of transgenic Dendrobium lasianthera has been developed for the first time. The 8-week-old protocorm explants were used as target of transformation with Agrobacterium tumefaciens strain LBA4404 carrying plasmid pG35SKNAT1. Several parameters such as infection period, Agrobacterium density, concentration of acetosyringone, and co-cultivation period were evaluated for the transformation efficiency. The data were analyzed using one-way analysis of variance (ANOVA) and Duncan's Multiple Range Test (DMRT) with p < 0.05. Subsequently, KNAT1 gene expression was confirmed by polymerase chain reaction (PCR) analysis. The highest efficiency of transformation (70%) obtained from protocorm explants infected with Agrobacterium culture was at the OD600 concentration of 0.6 for 30 min, and co-cultivated with acetosyringone 100 µM for 5 days. The results of confirmation by PCR analysis show that the KNAT1 gene has been integrated and expressed in the genome of Dendrobium lasianthera transgenic.