Judul: Studi Poliembrioni, Viabilitas Benih dan Identifikasi Genetik Semaian Jeruk Japansche Citroen (Citrus limonia Osbeck.) menggunakan SSR
Abstrak: Japansche Citroen (Citrus limonia Osbeck) or JC is citrus rootstock that is often used by Indonesian citrus farmer because its wide adaptation ability and has resistant to several diseases. JC seeds should have physical, physiological, genetic and health quality. Seed has maximum quality when it is reached at the time of physiological maturity. Seed maturity, in general is decided by physical appearance of fruit, such as rind colour changes. JC seeds have polyembryony characteristic; threrefore one or more embryos per seed consist of either zygotic embryo and or nucellar embryo. Nucellar embryo can be useful for clonal propagation. Nevertheles, there were off type seedling. It is necessary to identify seedling base on morphology and molecular marker such as SSR marker. Morphology marker was easy to used and cheap, but the trully genetic must be identify with SSR. SSR could differenciate between homozygot and heterozigot genotype. The aims of this research were to acquire information about poliembryony on JC citrus, to determine physiological maturity of JC seed base on rind colour and fruit hardness, to know the effect of fruits maturity to physical and physiological quality of seed, genetic quality and number of seedling, and to identify JC seedling base on morphology marker and SSR marker. The research was conducted in Indonesian Citrus and Subtropical Fruits Research Institute from April 2012 to January 2013. The research consisted of three experiments, there were 1) study on polyembryony of JC , 2) study on effect of fruits maturity level to physical and physiological quality of seed, genetic quality and number of seedling, and 3) identification of JC seedling base on morphology marker and SSR marker. Experiment I was conducted based on visual observations on each of 30 seeds of five maturity levels. Criteria of fruit maturity are 1) dark green rind, hard fruit (> 7 kg/cm2), 2) green yellow rind, rather hard (6-7 kg/cm2), 3) pieces of yellowish green rind, rather soft (5-5.9 kg/cm2), 4) >90% yellow rind, soft (4-4.9 kg/cm2) and 5) pieces of yellow-orange rind, very soft (< 4 kg/cm2). The experiment variable were seed coat colour, the mean number of embryos per seed, polyembryony seed percentage (%) and the dominant colour of the embryo. Experiment II used randomized completely block design (RCBD) one factor. The factor is five maturity level base on fruits maturity. The criteria of fruits maturity are equal to experiment I. Each treatment was repeated three times so that there was 15 units of experiments with experimental unit consisted of 100 seeds. The experiment variable were seed moisture content (%), dry weight of 10 seeds (g), vigor index (%), seed growth rate (%/etmal), germination percentage (%), the growth percentage (%), multiple seedling percentage (%), total seedlings, off type seedling percentage (%), and total true to type seedling. Data were analyzed with analysis of variance (ANOVA). If the results obtained by analysis of variance were significant different, then tested by Duncan's Multiple Range Test (DMRT) at 5% level. Experiment III was the identification of true to type seedlings and off type seedling with morphology marker and molecular markers. This experiment
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Judul: The Resistance of Citrus Rootstock Japansche Citroen to In Vitro Drought Stress Condition
Abstrak: Varietas batang bawah jeruk diharapkan dapat beradaptasi dengan baik dalam berbagai kondisi cekaman lingkungan. Seleksi in vitro menggunakan polietilen glikol (PEG) dapat digunakan untuk memperoleh individu yang toleran terhadap kekeringan. Penelitian ini bertujuan untuk mempelajari pengaruh penggunaan PEG sebagai agen penyeleksi terhadap pertumbuhan jeruk varietas Japansche Citroen pada kondisi cekaman kekeringan secara in vitro. Penelitian dilaksanakan di Laboratorium Kultur Jaringan 1, Departemen Agronomi dan Hortikultura, Institut Pertanian Bogor, Bogor. Penelitian dimulai pada bulan Desember 2019 hingga Februari 2021. Penelitian ini menggunakan metode rancangan kelompok lengkap teracak faktor tunggal yaitu konsentrasi PEG dengan empat taraf: 0 %, 5 %, 10 %, dan 15 %. Hasil pengamatan menunjukkan bahwa jumlah daun, jumlah akar, dan tinggi tanaman batang bawah jeruk menurun sebagai respon terhadap penambahan 5–15 % PEG pada media in vitro. PEG tidak berpengaruh nyata terhadap persentase kontaminasi, persentase hidup eksplan, dan panjang akar., Citrus rootstock varieties are expected to be well adapted in various environment stress condition. In vitro selection using polyethylene glycol (PEG) can be used to obtain drought stress tolerant individual. The objective of the experiment was to study the effect of using PEG as selector agent to the growth of citrus Japansche Citroen variety on in vitro drought stress condition. The experiment was conducted at Tissue Culture 1 Laboratory, Department of Agronomy and Horticulture, IPB University, Bogor. The experiment was started on December 2019 until February 2021. The experiment used randomized complete block design with one factor, PEG concentration which had four levels: 0 %, 5 %, 10 %, and 15 %. The result of observation showed that number of leaves, number of roots, and plant height of citrus rootstock decreased in response to the addition of 5–15 % PEG to in vitro media. PEG did not affect the contamination persentage, survival persentage, and length of root significantly.
Keyword: phytotoxic, growth, polyethylene glycol

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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