Judul: Determination of Seed Physiological Maturity of Kangkong (Ipomoea reptans Poir.) based on Phenology, Seed Quality and Heat Unit Accumulation
Abstrak: Periode masak fisiologis benih ditentukan berdasarkan studi fenologi fase berbunga hingga menjelang panen. Penelitian ini bertujuan untuk mendapatkan informasi tentang fenologi bunga, buah, dan biji serta mengetahui akumulasi satuan panas yang tepat untuk menentukan masak fisiologis benih kangkung darat (Ipomoea reptans Poir.) dimana mutu benih mencapai maksimum. Penelitian menggunakan rancangan percobaan rancangan kelompok lengkap teracak satu faktor yaitu umur panen kangkung darat yang terdiri atas 15 taraf. Hasil menunjukkan, masak fisiologis benih kangkung darat varietas KK-02 dicapai 25-26 HSA dengan ciri-ciri buah dan biji berwarna coklat tua setelah dikeringkan. Saat umur panen 25-26 HSA, kadar air benih cukup rendah (9% dan 9,8%), sedangkan bobot kering benih (4,55 g dan 4,53 g), viabilitas (daya berkecambah 87% dan 84%), serta vigor benih (indeks vigor 79,0% dan 84%, keserempakan tumbuh 84% dan 83,5%, serta laju pertumbuhan kecambah 118,11 dan 106,83 mg kecambah normal-1) mencapai maksimum. Satuan panas kangkung darat varietas KK-02 saat masak fisiologis benih berada pada kisaran 1668,50 - 1685,50 °Cd., The physiological maturity period of the seeds was determined based on phenological studies from the flowering phase until before harvest. This study aimed to obtain information about the phenology of flowers, fruits, and seeds as well as to determine the appropriate heat unit accumulation to determine the seed physiological maturity of kangkong (Ipomoea reptans Poir.) where the maximum seed quality achieved. This study used an Randomized Complete Block design with one factors, namemly the seed harvesting time consisted of 15 levels. The results showed that the seed physiological maturity of kangkong cv KK-02 was achieved at 25-26 DAA with the characteristics of fruit and seeds dark brown color after drying. At 25-26 DAA, the seed moisture content was quite low (9% and 9.81%) while the seed dry weight (4.55 g and 4.53 g), seed viability (87% and 84% germination), and seed vigor (79.0% and 83.5% vigor index, 84% and 83.5% synchronization of germination, and 118.11 and 106.83 mg normal seedling growth rate-1) reached their maximum. Heat unit of kangkong cv KK-02 at the seed physiological maturity was 1668.50 - 1685.50 °Cd.
Keyword: bobot kering benih, umur panen, viabilitas benih, vigor benih, harvest time, seed dry weight, seed viability, seed vigor

Judul: Determination of Short Term Storage to Maintain Quality of Water Spinach Seeds (Ipomoea reptans Poir.)
Abstrak: Benih yang dipanen saat masak fisiologis akan memiliki mutu yang maksimal. Benih perlu disimpan pada kondisi yang optimum untuk mempertahankan mutunya. Penelitan ini bertujuan menetapkan kondisi simpan jangka pendek benih kangkung sehingga mutunya dapat dipertahankan. Rancangan yang digunakan adalah rancangan acak lengkap faktorial dua faktor dengan 4 ulangan. Faktor pertama adalah warna benih kangkung yaitu hitam, cokelat gelap, dan cokelat terang. Faktor kedua adalah ruang simpan yaitu ruang ber-AC (suhu 16 - 21 °C, RH 55 – 63%) dan ruang kamar (suhu 27,4 – 30,3 °C, RH 64 - 87%). Setiap ulangan terdiri atas 25 benih. Hasil penelitian menunjukkan bahwa benih kangkung darat berwarna hitam dan cokelat gelap telah mencapai masak fisiologis, sehingga viabilitas dan vigor lebih tinggi dibandingkan warna cokelat terang. Benih berwarna cokelat terang belum mencapai masak fisiologis, dan memiliki viabilitas yang rendah. Ruang ber-AC (suhu 16 - 21 °C, RH 55 – 63%) dan ruang kamar (suhu 27,4 – 30,3 °C, RH 64 - 87%) dapat digunakan untuk mempertahankan mutu benih kangkung darat yang dikemas dalam aluminium foil dengan kadar air awal 9% untuk penyimpanan jangka pendek (14 minggu)., The seed quality is highest when it reaches physiological maturity. In order to maintain the quality, the seed needs to be stored in an optimum condition. The study was aimed to determine the proper short term storage conditions for kangkong seeds for maintaining the quality. This study was arranged in a completely randomized design with two factors and repeated 4 times. The first factor was seed coat color i.e. black, dark brown, and light brown and the second factor was the storage condition i.e. air-conditioned room (temperature 16-21 °C, RH 55-63%) and ambient room (temperature 27,4 – 30,3 °C, RH 64 - 87%). Each replicates consisted of 25 seeds. The results showed that the black and dark brown colors of kangkong seeds has reached physiological maturity therefore had higher viability and vigor than that of the light brown seeds. The light brown seed is physiologically immature, and have low viability. For short term storage (14 weeks) air-conditioned room (temperature 16-21 °C, RH 55-63%) and ambient room (temperature 27,4 – 30,3 °C, RH 64 - 87%) were sufficient to maintain the quality of kangkong seeds packed in aluminium foil with 9% initial moisture content.
Keyword: seed coat color, storage condition, viability, vigo

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: