Judul: Isolasi dan Karakterisasi Bakteri Penghasil Indole-3-Acetic Acid (IAA) yang Berasal dari Area Penambangan Batu Kapur.
Abstrak: Soil degradation due to limestone activity can be overcome by planty plant reclamation. The growth of seedling plants reclamation can be induced to grow well on nutrient-poor and alkaline soil condition by using the indigenous bacteria, such as IAA producing bacteria. The research was aimed to isolate and characterize Indole-3-acetic acid (IAA) producing bacteria from limestone quarry. Isolation was performed on 13 soil samples of limestone quarry, and then 25 isolates were obtained. The selection by hypersensitive test showed 2 isolates used to test further, namely isolate QC 5C32 and QC 7B41. Both isolates were identified by KIT API 50 CH, a series of biochemistry reaction had 99.9% similarity with Bacillus megaterium, had rod-shapes, Gram positive, and produced endospore. The highest IAA production occured by adding 1.5 mM of Ltryptophan. The result showed that amount of IAA was 10.345 ppm (QC 5C32) and 18.723 ppm (QC 7B41). Application of both isolates toward siratro (Macroptilium atropurpureum) showed impact to the growth of primary root, number of lateral root, and fresh weight of siratro root sprout.
Keyword: Bacillus megaterium, Plant growth promoting rhizobacteria (PGPR), reclamation

Judul: Isolasi dan Karakterisasi Rhizobakteri Penghasil Indole-3-Acetic Acid (IAA) dari Tanah Penanaman Bawang Merah
Abstrak: Rhizobakteri pemacu pertumbuhan tanaman (Plant Growth Promoting Rhizobacteria/PGPR) telah diketahui mempunyai peran penting dalam kesuburan tanah dan penyehatan tanaman. Mekanisme PGPR dalam memacu pertumbuhan tanaman salah satunya dengan mensekresikan zat pemacu tumbuh tanaman seperti Indole-3-Acetic Acid (IAA). Rhizobakteri penghasil IAA ini diisolasi dari rhizosfer tanaman bawang merah (Allium cepa) di daerah Brebes, Jawa Tengah. Penelitian ini dilakukan untuk mendapatkan isolat rhizobakteri penghasil IAA yang potensial dan melakukan karakterisasi morfologi bakteri. Metode penelitian ini meliputi pengambilan sampel tanah, isolasi bakteri penghasil IAA, pengukuran IAA dengan menggunakan uji kolorimetri, pewarnaan gram, penentuan kurva pertumbuhan dan produksi IAA, uji hemolisin, uji hipersensitivitas, dan aplikasi bakteri terpilih pada kecambah kacang hijau. Sebanyak 14 isolat bakteri penghasil IAA berhasil diisolasi. Beberapa isolat mampu menghasilkan IAA berdasarkan uji kolorimetri dengan konsentrasi tertinggi 61.72 ppm (BIT 2.4), 60.92 ppm (BIS 3.4) dan 49.30 ppm (BIT 2.1) sedangkan konsentrasi terendah 4.27 ppm (BIT 4.1). Hasil pewarnaan gram menunjukkan keempat isolat (BIS 3.4, BIT 2.4, BIT 2.1, BIT 4.1) bersifat Gram positif. Isolat BIS 3.4 dan BIT 2.1 menghasilkan IAA tertinggi sebesar 59.84 ppm dan 8.81 ppm masing-masing pada fase stasioner. Hasil uji hipersensitivitas terhadap daun tembakau menunjukkan hasil negatif pada isolat BIS 3.4 dan BIT 2.1 yang diujikan. Kedua isolat tidak menyebabkan nekrosis pada tanaman tembakau dan tidak menghasilkan hemolisin. Hasil pengujian isolat BIS 3.4 dan kontrol menunjukkan tidak berpengaruh nyata terhadap panjang akar utama dan jumlah akar lateral kecambah kacang hijau setelah 7 hari tanam.
Keyword: Allium cepa, hipersensitivitas, rhizosfer, tembakau, tembakau

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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