Judul: Kemampuan bakteri endofit Micrococcus endophyticus G053 dalam memproduksi IAA-like compound dan meningkatkan pertumbuhan tanaman
Abstrak: Endophytic bacteria are able to act as PGPB (plant growth-promoting bacteria) by producing hormones or increasing availability nutrients for plants. This study aimed to test the ability of endophytic bacterium Micrococcus endophyticus G053 to produce IAA-like compound, fix free nitrogen, and its ability to increase potato plantlet and tobacco plant growth. The ability of M. endophyticus G053 to produce IAA-like compound in TSB 50% and TSB 100% was tested using Salkowski reagent, whereas its ability to fix free nitrogen was tested by growing it in LGI agar. Potency of M. endophyticus G053 to increase plants growth was tested in vitro using potato plantlets and in planta using tobacco plants. The results showed that M. endophyticus G053 was able to produce IAAlike compound in both media and to fix free nitrogen. The highest production of IAA-like compound was at 6th day of incubation in TSB 50% (64.35 ppm) and at 8th day of incubation in TSB 100% (69.10 ppm). Potato plantlets inoculated with M. endophyticus G053 was able to increase plantlet height and its number of shoot. M. endophyticus G053 inoculated in tobacco plants rhizosphere was also able to increase shoot length, root length, and dry weight of tobacco plants. The ability of M. endophyticus G053 to increase potato plantlets and tobacco plants growth was due to their ability to produce IAA-like compound and to fix free nitrogen.
Keyword: Bogor Agricultural University (IPB), nitrogen-fixing bacteria, Micrococcus endophyticus G053, indole-3-acetic acid (IAA), endophytic bacteria

Judul: Kemampuan aktinomiset endofit dalam meningkatkan pertumbuhan tanaman padi (Oryza sativa L.) melalui aktivitas asam Indol Asetat
Abstrak: Actinomycetes endophyte lives in plant tissue and may be able to produce various bioactive compounds. The bioactive compound produced by Actinomycetes endophyte can be useful to enhance the growth of plant through the activity of phytohormones substances produced, i.e. indole Acetic Acid (IAA). In vitro production of IAA from the ten isolates that were grown in ISP 2 liquid medium with the addition of 0.2 ml L-tryptophan 0.2% showed various concentration ranging about 11-99 ppm. Isolates producing high IAA were AB131-1 (99.2 ppm), AB131-2 (99,2 ppm), and PS4-16 (93.4 ppm). Those three superior isolates were then inoculated into rice seedlings which were then grown in pouches. Inoculation were designed in 20 different treatments, i.e. negative control, positive control (IAA 0.01, 0.1 dan 1 ppm), media control of ISP 2 liquid medium and supernatant of the three isolates in various concentrations. AB131-1 (1.05 ppm IAA) was considered as the most potential isolate based on its capability to increase plant height (26%), root length (33.4%) and dry weight (206%) more than the influence of IAA sintetic of 0.1 ppm addition. Microscopic observation of AB131-1 and PS4-16 of rice treatment using root coloring and Scanning Electron Micrographs (SEM) method showed that both of isolate were able to penetrate to the root of rice. The data showed that the application of Actinomycetes endophytic can increase the growth of rice plant.
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Judul: Hamiltonian formulation for linear waves motion in two layers fluid
Abstrak: The surface wave could be considered as a wave that separates two fluids, namely water and air. Based on this assumption, it is introduced the interfacial wave, a wave between two layers of fluid with different density. The formulation of interfacial waves motion begins with deriving the base equation of irrotational ideal fluid. Furthermore, according to irrotational fluid assumption, the base equation can be stated in velocity potential. In this derivation, the fluids domain is assumed to be restricted by rigid lid boundary conditions, both at the upper and lower limit. Therefore, the interfacial waves motion can be explained in a hamiltonian formulation. In the hamiltonian formulation, total energy is defined as the sum of kinetic and potential energy. The hamiltonian system is obtained from reduction of kinetic energy by using the Dirichlet Neumann Operator. The resulted kinetic energy equation is nonlinear. Therefore, this form is linearized by first part of the Taylor expansion. This linearization gives a dispersion relation of linear wave. Based on this dispersion relation, the phase speed of the linear wave depends on the density ratio of the two layers fluid.
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