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 Harvest Time for Water Spinach Seeds (Ipomoea reptans Poir.) based on The Stage of Maturation
Abstrak: Panen yang dilakukan serempak menghasilkan benih kangkung darat dengan tingkat kemasakan beragam. Benih belum masak bermutu rendah, sementara benih lewat masak cenderung mengalami seed coat-imposed dormancy. Oleh karena itu waktu panen perlu ditetapkan untuk mendapatkan proporsi benih mencapai masak fisiologi terbesar. Penelitian ini bertujuan mempelajari pola pembungaan tanaman kangkung dan menentukan umur panen serentak untuk mendapatkan proporsi benih masak fisiologi tertinggi. Penetapan waktu panen dilakukan dalam Rancangan Kelompok Lengkap Teracak (RKLT) satu faktor, yaitu waku panen yang terdiri atas 24, 26, 28, dan 30 hari setelah antesis (HSA). Hasil penelitian menunjukkan puncak pemunculan kuncup bunga terjadi pada 42-68 HST dan mulai mekar pada 51-60 HST. Bunga mekar satu hari, terjadi pada 10-11 setelah kuncup muncul dan buah masak sekitar 30 hari setelah bunga mekar. Fruit set berkisar 86±0,24% dan seed set berkisar 72±0,23%. Panen serentak menghasilkan benih dengan warna berbeda, yaitu coklat terang (belum masak), coklat gelap (masak) dan hitam (lewat masak). Daya berkecambah benih cokelat gelap dan hitam > 80%, sementara benih cokelat terang sekitar 66%. Benih masak fisiologi ditandai berwarna coklat gelap, dicapai pada 20-30 hari setelah bunga mekar. Panen pada 24 HSA dan 26 HSA menghasilkan proporsi benih coklat gelap tertinggi., Water spinach seeds are harvested at once; when the whole plant is removed from the field. Consequently, the seeds are of various maturity levels, including overripe seeds that tend to experience seed coat-imposed dormancy. This study aimed to study flowering patterns and to determine the suitable harvest time in order to obtain the highest proportion of physiologically matured seeds. The research was arranged in a randomized complete block design with one factor, time of harvest, i.e., 24, 26, 28, and 30 days after anthesis (DAA). The results showed that the peak of flower bud emergence occurred at 42-68 DAP and began to bloom at 51-60 DAP. The flowers only bloom one day, occurring 10-11 days after the buds appear and the fruit ripens about 30 DAA. Fruit set around 86±0,24% and seed set 72±0,23%. Harvesting the seeds at once resulted seeds with different colors, light brown (immature), dark brown (ripe) and black (ovveripe). The germination rate of dark brown and black seeds is >80%, while light brown seeds are around 66%. Physiologically mature seeds are marked with a dark brown color, reached 20-30 DAA. Harvesting at 24 DAA and 26 DAA produced the highest proportion of dark brown seeds.
Keyword: antesis, black seeds, dark brown seeds, flowering,light brown seed

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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