Judul: Characterization and evaluation of seeded and seedless Indonesian pummelo {citrus maxima (burm.) Merr.} accessions
Abstrak: Indonesia has many accessions of pummelo germplasms, but only a small number of the accessions are planted commercially. Genetic variation in the seed number per fruit in pummelo is high, ranging from seedless to very seedy. Thus pummelo is categorized as seeded, potentially seedless and seedless. The objectives of this research were: 1) to identify morphological, biochemical (isozyme) and molecular (ISSR) characters, and ploidy level of seeded and seedless pummelo accessions originated from Sumedang, Pati, Kudus and Magetan, 2) to identify fruit formation of seeded and seedless pummelo, 3) to evaluate fruit quality of seeded and seedless pummelo fruit quality during storage. The characterization research showed that morphological characters contributed in grouping pummelo accessions were epicarp thickness, leaf lamina margin, vesicle length, epicarp color, petiole wing width and fruit shape, while based on isozyme characters were MDH (Rf 0.11 and 0.14) and ACP (Rf 0.24 and 0.33). ACP band at Rf 0.24 could be used as marker to differentiate seeded and seedless pummelo accessions. Molecular characters supported in classification of pummelo accessions were PKBT8 500 bp, PKBT8 375 bp, PKBT7 750 bp, PKBT3 750 bp, PKBT8 625 bp and PKBT12 500 bp. Separation between seeded and seedless cultivars based on morphological characters occured at similarity coefficient of 0.63, while on isoenzyme characters occured at similarity coefficient of 0.49. Both seeded and seedless pummelo accessions were diploid (2n = 2x = 18). Observation on fruit formation between selected seeded and seedless pummelo demonstrated that those pummelo accessions were able to produce parthenocarpic fruits, but bored seeded fruits when self pollination was induced, thus indicated self-compatibility. Natural self-pollination on ‘Bali Merah 1’, ‘Bali Merah 2, ‘Nambangan’ and ‘Bageng’ yielded seedless fruits, but most of ‘Jawa 3’ was seeded. Artificial self-pollination on those accessions produced seeded fruits, thus showed ovule fertility. ‘Bali Merah 2’ was shown to have high parthenocarpic degree as indicated by less seed number (<10 seed per fruit) in all pollination treatments. Therefore seedlessness in those pummelo accessions was caused by parthenocarpy, was not by pollen and ovule sterility, selfincompatibility, or poliploidy. Evaluation of pummelo fruit quality showed seedless pummelos have higher vitamin C, naringin content and acidity than seeded accessions. Vitamin C and titratable acidity (TA) content decreased, but total soluble solids (TSS) and TSS/AT ratio increased during storage period. During storage, percentage of edible portion increased, mainly due to the decrease of peel weight. Percentage of fruit axis of seedless accessions was smaller than those of seeded accessions. Sensory analysis indicated ‘Jawa 1’ seedless accessions have superior quality based on hedonic and scale quality test.
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Judul: Evaluation of N, P and K Nutrient Pummelo Citrus Plantation (Citrus maxima (Burm.) Merr.)  in Pangkep with Nutrient Symptom Deficiency Methods, Plant Analysis and Soil Test Methods
Abstrak: Jeruk pamelo (Citrus maxima (Burm.) Merr.) merupakan salah satu buah yang digemari konsumen serta memiliki nilai ekonomi yang tinggi. Kabupaten Pangkep menjadi penghasil jeruk pamelo terbesar di Sulawesi Selatan namun, mengalami penurunan pada tahun 2018, 2019, dan 2020. Penurunan produksi dipengaruhi ketidakseimbangan hara esensial yaitu hara N, P dan K di dalam tanah. Penelitian ini bertujuan mengevaluasi status hara N, P dan K tanah kebun jeruk pamelo di Kabupaten Pangkep. Metode yang digunakan adalah gejala defisiensi hara, analisis tanaman, dan uji tanah. Tahapan awal dilakukan pengamatan gejala defisiensi hara pada daun yang memiliki ciri-ciri secara visual dan disesuaikan dengan pedoman kemudian diperkuat dengan analisis daun untuk menetapkan konsentrasi hara N, P dan K. Sampel tanah komposit diambil dari lokasi yang tanamannya tumbuh normal dan yang mengalami gejala defisiensi kemudian dianalisis untuk mengetahui kadar N, P dan K. Hasil analisis tanah menunjukkan N dan K berstatus rendah, baik pada jeruk pamelo tumbuh normal dan yang mengalami defisiensi N dan K. Tanaman yang menunjukkan gejala defisiensi N dan K menunjukkan analisis tanaman yang juga rendah. Gejala defisiensi secara visual P tidak ditemukan di lapangan dan hasil analisis tanaman menunjukkan konsentrasi P tergolong tinggi, walaupun hasil analisis tanah menunjukkan konsentrasi P yang tergolong rendah., Pummelo citrus (Citrus maxima (Burm.) Merr.) is one of the fruits that is favored by consumers and has a high economic value. Pangkep is the largest producer of pummelo citrus in South Sulawesi. The production, however, declined in 2018, 2019 and 2020. The decrease in production is influenced by the imbalance of nutrients N, P and K in the soil. The purpose of this study was to evaluate the status of nutrients N, P and K of pummelo citrus plantation in Pangkep. The methods used were symptoms of nutrient deficiency, plant analysis, and soil testing. The research was started by visual observation of N, P and K deficiency symptoms in leaves. Composite soil samples were taken from locations where plants grew normally and which had N, P or K deficiency symptoms. These samples were then analyzed to find out the levels of N, P and K. Soil analysis showed that N and K status were low in both, normal growing and N and K deficient pummelo citrus. Plants showing N and K deficiency symptoms showed low plant analysis. Visual deficiency symptoms of P were not found in the field and plant analysis results showed high concentrations of P, although soil analysis results showed low concentrations of P.
Keyword: leaves, fertilization, production

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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