Judul: The Potential of Dark Septate Endophyte Fungi in Enhancing Soybean Tolerance to Aluminum Stress
Abstrak: The soybean productivity in Indonesia remains low due to limited cultivation land, with most available land being acidic dry land. However, this type of land has low pH and moderate to high aluminum (Al) content, adversely affecting soybean growth. Dark Septate Endophyte (DSE) fungi have been reported to promote plant growth under biotic and abiotic stress conditions. This study aims to evaluate the potential of DSE and investigate its mechanism in enhancing soybean tolerance to Al stress. Only non-pathogenic DSE strains were analyzed for their potential in vitro on soybean seedlings of the Argomulyo, KH 42, and Demas 1 cultivars at Al concentrations of 0,5 mM and 0,9 mM. The results showed that two DSE strains could increase plant height, fresh weight, and dry weight under 0,5 mM Al stress, although these increases were insignificant compared to the control. DSE is thought to colonize root tissues massively, reducing Al binding in root tissues and forming microsclerotia. The varied growth responses of soybean plants indicate a complex interaction between soybean plants, DSE fungi, and aluminum stress., Produktivitas kedelai dalam negeri masih rendah, karena lahan budidaya terbatas dan lahan yang banyak tersedia adalah lahan kering masam. Lahan tersebut memiliki pH rendah dan kandungan aluminium (Al) sedang sampai tinggi yang berpengaruh buruk terhadap pertumbuhan kedelai. Cendawan Dark Septate Endophyte (DSE) dilaporkan mampu memacu pertumbuhan tanaman pada kondisi cekaman biotik dan abiotik. Penelitian ini bertujuan mengevaluasi potensi DSE dan menduga mekanismenya dalam meningkatkan toleransi tanaman kedelai terhadap cekaman Al. Hanya strain DSE non-patogenik terhadap kedelai yang dianalisis potensinya secara in vitro pada bibit kedelai Argomulyo, KH 42 dan Demas 1 pada konsentrasi Al 0,5 mM dan 0,9 mM. Hasil penelitian menunjukkan dua strain DSE mampu meningkatkan pertumbuhan tinggi, bobot basah dan kering tajuk pada cekaman Al 0,5 mM, meskipun tidak signifikan terhadap kontrol. DSE diduga mengkolonisasi jaringan akar secara masif hingga mengurangi pengikatan Al di jaringan akar dan membentuk mikrosklerotia. Respons pertumbuhan tanaman kedelai yang beragam menunjukkan hubungan kompleks antara tanaman kedelai, cendawan DSE dan cekaman aluminium.
Keyword: in vitro, pathogenicity test, soybean growth

Judul: Respon pertumbuhan tanaman kedelai [Glycine max (L.) Merr.] pada kondisi kekeringan dan cekaman aluminium
Abstrak: The government has launched the soybean self sufficiency by 2014 in an effort to enough needs domestic of soybean . This will be achieved by increased productivity , expansion of cropping intensity and extension of planting area. A extension of the planting area is to utilize marginal lands. The mostly marginal lands in Indonesia is dryland acid soil and has the potential to be developed as an extension of planting area. The cultivation in dryland acid soil had several constraints, such as drought and high solubility of Al3+. The soybean response to water deficit varies depending on the genotypes, and the duration of the stress and growth phase. High solubility of Al3+ in the soil inhibits root growth. The experiment was carried out to study the growth response and the mechanisms of adaptation the soybean genotypes to drought and aluminum stress, which consists of the two stages experiments. The first stage was carried out to study the effect of genotype, drought and aluminium stress on the vegetative and generative growth and the plant roots of soybean. The second stage was carried out to study the effect of genotype, drought and aluminium stress on component crops of soybean. This experiments was conducted in Januari to November 2011, in the greenhouse Cikabayan, University Farm, IPB Darmaga Bogor. This study used a randomized complete block design, with three factors: 1) soybean genotypes (SP 30-4, Anjasmoro, PG 57-1 and Tanggamus), 2) watering interval (2 days, 6 days and 10 days, 3) the level of Al neutralization (0% neutralization and 100% neutralization). The results show that the adaptation mechanism avoidance of soybean geno types was only seen in PG57-1 on root length variables when gripped by drought. This mechanism can be seen from its root elongation when gripped by drought. The higher of value of the observed variables would be the higher the number of pods produced. It also happens to variable root dry weight and dry weight of root nodules. In general, yield components of soybean more influenced by drought stress. However, flowering only variable affected by Al stress on different genotypes.
Keyword: aluminium stress, drought stress, the mechanisms of adaptation

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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