Judul: Regulasi Etilen dalam Respon Tanaman Sorgum (Sorghum bicolor (L.) Moench) terhadap Cekaman Toksisitas Fe
Abstrak: Lahan pasang surut merupakan salah satu lahan marginal di Indonesia. Persoalan utama pada lahan tersebut adalah cekaman toksisitas Fe. Sorgum (Sorghum bicolor (L.) Moench) adalah tanaman pangan yang dapat tumbuh di lahan marginal termasuk juga lahan pasang surut. Tingkat toleransi sorgum terhadap cekaman toksisitas Fe berbeda antar genotipe sorgum dan mekanisme yang terjadi didalamnya masih belum jelas. Etilen sebagai salah satu hormon tumbuhan berperan penting dalam mengatur respon tanaman pada beberapa cekaman abiotik. Tujuan dari penelitian ini adalah untuk mempelajari peran etilen dalam respon tanaman sorgum terhadap cekaman toksisitas Fe. Penelitian ini dilaksanakan di rumah kaca kebun percobaan Cikabayan (240m dpl) pada bulan Juni hingga Agustus 2016. Terdapat dua percobaan dengan menggunakan dua genotipe yang berbeda, yaitu Numbu dan Pahat. Numbu adalah genotipe yang toleran, sedangkan Pahat adalah genotipe yang peka terhadap cekaman Fe. Setiap percobaan disusun menggunakan Rancangan Kelompok Lengkap Teracak (RKLT) dengan dua faktor dan tiga ulangan. Faktor yang digunakan adalah konsentrasi Fe yaitu 0 dan 200 ppm, dan konsentrasi etepon yaitu 0, 12, 24, 48 ppm. Hasil dari penelitian ini didapatkan perbedaan respon genotipe Numbu dan Pahat terhadap toksisitas Fe, pemberian etepon, dan interaksi antara Fe dan etepon. Dampak dari toksisitas Fe lebih besar terhadap genotipe Pahat dibandingkan genotipe Numbu yang dibuktikan dengan Indeks Toleransi Cekaman Numbu yang lebih tinggi dan persentase gejala bronzing yang lebih rendah dibandingkan genotipe Pahat. Respon genotipe Numbu terhadap pemberian etepon lebih besar pada tinggi tanaman, dan lebih kecil pada diameter batang, panjang akar, dan jumlah daun dibandingkan dengan genotipe Pahat. Terdapat interaksi antara toksisitas Fe dengan penambahan etepon. Pengaruh interaksi lebih besar pada genotipe Pahat dibandingkan dengan genotipe Numbu yang dibuktikan oleh perubahan relatif yang lebih besar pada semua karakter pertumbuhan. Hasil ini mengindikasikan pengaruh Fe pada tanaman dipengaruhi oleh respon tanaman terhadap etilen.
Keyword: cekaman abiotik, etepon, toleransi

Judul: Regulasi Etilen dalam Respon Tanaman Sorgum [Sorghum bicolor (L.) Moench.] terhadap Cekaman Defisiensi P dan Toksisitas Al
Abstrak: Understanding the tolerance mechanism of sorghum [Sorghum bicolor (L.) Moench] to aluminium (Al) toxicity and phosphorus (P) deficiency is of high importance to assists breeding program of acid soil-tolerant sorghum. The objective of this research was to study the role of ethylene in the response of sorghum to Al toxicity and P deficiency. This research was conducted in Cikabayan Experimental Field from March to June 2013. This research consisted of two experiments. The first experiment was aimed to determine etephon concentration that could distinguished Al accumulation in the root of Numbu (toleran) and B69 (sensitive) genotypes by haematoxylin staining. The Numbu and B69 seedlings were grown hydroponically for two days in the nutrient solutions containing 0 and 74 μM AlCl3, and different levels of etephon concentrations (i.e. 0, 12.5, 25 and 50 ppm). The first experiment result showed that under 74 μM AlCl3, 12.5 ppm etephon could distinguished the Al accumulation in Numbu and B69 root tip. The second experiment was arranged in randomized completely block design with two factors and three replications. The first factor was P availability and Al toxicity, consisted of four levels i.e. low-P (0.001 mM KH2PO4), sufficient-P (0.1 mM KH2PO4), low-P + 74 μM AlCl3, and sufficient-P +74 μM AlCl3. The second factor was the exogenous application of ethylene regulator, consisted of three levels i.e. control (without ethylene regulator), ethylene precursor (12.5 ppm ethepon), and ethylene action inhibitor (0.6 μM AgNO3). Two sorghum genotypes (Numbu and B69) were grown hydroponically for 14 days. The results showed that Numbu, the acid soil tolerant genotype, was less affected by the P-availability and Al toxicity. In contrast, low-P and Al toxicity significantly decreased root- and shoot length, and shoot- and root-fresh weight of B69, the acid soil sensitive genotype. Application of exogenous ethylene significantly decreased root length, while application of ethylene action inhibitor significantly increase root length in Numbu genotype but not in B69 genotype, indicating that Numbu was more responsive to ethylene. Inhibition of ethylene action under low-P and Al toxicity caused growth inhibition in B69 genotype. Taken together our results imply that the different tolerance to acid soil of Numbu and B69 genotype might be caused by the different responsiveness to ethylene.
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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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