Judul: Effect of bacteria Micrococcus endophyticus G053 and Bacillus sp. L-12 on the Growth of Potato Cultivar Jala Ipam
Abstrak: Umbi kentang kultivar Jala Ipam sangat cocok untuk kentang goreng. Micrococcus endophyticus G053 dan Bacillus sp. L-12 merupakan bakteri endofit yang mampu meningkatkan pertumbuhan tanaman. Inokulasi bakteri endofit ke planlet kentang kultivar Jala Ipam in vitro diharapkan dapat meningkatkan pertumbuhannya. Penelitian ini bertujuan untuk menganalisis pengaruh Micrococcus endophyticus G053 dan Bacillus sp. L-12 terhadap pertumbuhan kentang kultivar Jala Ipam. Inokulasi bakteri dilakukan pada planlet kentang Jala Ipam yang berumur 2 MST (minggu setelah tanam). Setelah 4 MST, planlet disubkultur untuk mengetahui pengaruh inokulasi endofit pada pertumbuhan planlet hasil subkultur dan keberadaan bakteri endofit. Inokulasi bakteri endofit Micrococcus endophyticus G053 dan Bacillus sp. L-12 meningkatkan pertumbuhan tajuk dan akar planlet kentang. Setelah dua minggu inokulasi, kedua bakteri endofit masih terdapat pada planlet dan dapat tumbuh dengan baik. Subkultur planlet kentang kultivar Jala Ipam menunjukkan bahwa planlet yang sebelumnya diinokulasi dengan kedua bakteri endofit tersebut mempunyai pertumbuhan yang cenderung lebih baik dari pada planlet yang sebelumnya tidak diinokulasi dengan endofit. Hasil ini menunjukkan bahwa bakteri endofit M. endophyticus G053 dan Bacillus sp. L-12 mempunyai pengaruh meningkatkan pertumbuhan planlet kentang kultivar Jala Ipam dan dapat bertahan hidup dengan baik di dalam planlet secara in vitro., The tuber of potato cultivar Jala Ipam is suitable for french fries. Micrococcus endophyticus G053 and Bacillus sp. L-12 are endophytic bacteria that can improve plant growth. The inoculation of endophytic bacteria into the plantlet of potato cv Jala Ipam in vitro is expected to increase its growth. This study aimed to analyze the effect of Micrococcus endophyticus G053 and Bacillus sp. L-12 on the plant growth of potato cv Jala Ipam in vitro. Inoculation of bateria was carried out on the plantlets two weeks after planting (WAP). After 4 WAP, the plantlets were subcultured to determine the effect of endophytic inoculation on the growth of subcultured plantlets and the presence of endophytic bacteria. Inoculation of the endophytic bacterias Micrococcus endophyticus G053 and Bacillus sp. L-12 increased the shoot and root growth of the potato plantlets. After two weeks ofinoculation, both endophytic bacteria were still present in the plantlets and could grow well. The subculture of plantlets of potato cv Jala Ipam showed that the plantlets previously inoculated with endophytic bacteria had better growth than those that were not inoculated. These results indicate that the endophytic bacteria M. endophyticus G053 and Bacillus sp. L-12 have the effect of increasing the growth of plantlets of potato cv Jala Ipam and can survive well in the plantlets in vitro.
Keyword: Bacillus sp. L-12, kentang kultivar Jala Ipam, Micrococcus endophyticus G053, pertumbuhan tanaman

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: 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.
Keyword: