Judul: Interaction between Black Potato (Plectranthus rotundifolius (Poir.) Spreng.) and Chili (Capsicum annum L.) in Ex  Vitro Intercropping Experiment.
Abstrak: Potato and chili are important vegetable commodities in Indonesia. Both are often cultivated in intercropping system. One type of potato is the black potato which is easy to grow on any land. Hybrid red chili varieties TM-999 can be planted in the rainy and dry season. These two plant species were used in this research. This study aimed to revealthe effect of the interaction between black potato and chili plants on their growth in an ex vitro intercropping system, as well as it’s effects on the morphology and histology of the roots. The research method used a completely randomized design (CRD) with two treatments. Both plants were grown on Hoagland liquid medium in 200 mL culture bottles. Control treatment (K) was performed by planting both plant species in monoculture (5 weeks); the first treatment (P1) was the two plant species were planted in monoculture (2 weeks), then the media were exchanged and the growth was observed (3 weeks); and the second treatment (P2) was by planting the two plant species side by side on one medium (5 weeks). The results showed an interaction effect between the two plants, which stimulated the growth of potato plants. However, in chili plants this interaction inhibited their growth. This indicated the presence of allelochemical compounds generated from the interaction between both plants. The allelopathic effect inhibits root growth of potato and chili. Root became thicker and brown, and histology observations demonstrated a color difference between roots in control treatment (K) and in the two other treatments., Kentang dan cabai merupakan komoditas sayuran penting di Indonesia, keduanya sering dibudidayakan dengan sistem tumpangsari. Salah satu jenis kentang yaitu kentang hitam mudah tumbuh pada lahan apapun. Cabai merah hibrida varietas TM-999 dapat ditanam pada musim hujan dan kemarau. Kedua jenis tanaman ini dipergunakan sebagai bahan penelitian. Penelitian ini bertujuan untuk mengetahui efek interaksi antara tanaman kentang hitam dan cabai terhadap pertumbuhan keduanya dalam sistem tumpangsari secara ex vitro, serta pengaruhnya terhadap morfologi dan histologi akar tanaman tersebut. Metode penelitian menggunakan Rancangan Acak Lengkap (RAL) dengan dua perlakuan dan satu kontrol. Kedua tanaman ditanam pada media cair Hoagland dalam botol kultur berukuran 200 mL. Perlakuan kontrol (K) berupa kentang dan cabai ditanam secara monokultur (5 minggu); perlakuan pertama (P1), kedua jenis tanaman ditanam secara monokultur (2 minggu), kemudian media tanam keduanya saling ditukar, lalu pertumbuhannya diamati (3 minggu); dan perlakuan kedua (P2), kedua jenis tanaman ditanam berdampingan pada satu media (5 minggu). Hasil penelitian menunjukkan adanya efek interaksi antara kentang hitam dan cabai bersifat menstimulus pertumbuhan tanaman kentang. Namun, pada tanaman cabai, efek interaksi ini menghambat pertumbuhannya. Hal ini mengindikasikan adanya senyawa alelokimia yang berasal dari interaksi antartanaman. Efek alelopati juga menghambat pertumbuhan akar. Morfologi akar menjadi lebih tebal dan berwarna cokelat, dan pada pengamatan histologi akar terdapat perbedaan warna antara kontrol (K) dan kedua perlakuan.
Keyword: allelopathy, histology, intercropping, morphology, vegetative growth

Judul: Optimization of Planting Time for Three Varieties of Cayenne Pepper (Capsicum frustencens L.) in an Intercropping System with Sweet Corn (Zea mays L.)
Abstrak: Cabai rawit (Capsicum frutescens L.) adalah tanaman hortikultura yang memiliki nilai ekonomi tinggi. Dalam budidaya cabai, alih fungsi lahan menyebabkan penurunan luas panen. Salah satu cara untuk mengatasi masalah ini adalah dengan menerapkan pola tanam tumpangsari di lahan yang berada di bawah tegakan pohon atau dengan menanam tanaman cabai di lahan yang ditanam jagung. Mencari waktu tanam yang presisi dan varietas yang sesuai pada pola tanam tumpangsari merupakan tujuan dari penelitian ini. Penelitian ini menggunakan rancangan petak tersarang (nested design) dengan 2 faktor perlakuan yaitu waktu tanam dengan empat taraf yaitu kontrol: monokultur cabai rawit, 0, 4, 6 minggu setelah tanam jagung (MSJ) sebagai petak utama dan varietas cabai yaitu Bonita, Shadiva, dan Lobita sebagai anak petak. Pelaksanaan penelitian meliputi penyemaian, pengolahan lahan, penanaman, pemeliharaan, dan panen. Hasil dari penelitian ini menunjukan waktu tanam 0 MSJ berpengaruh signifikan pada peningkatan tinggi tanaman terutama pada varietas Shadiva dan menunjukan indikasi etiolasi akibat periode nanungan yang lebih lama dibandingkan waktu tanam lainnya. Nilai produktifitas pada waktu tanam 4 MSJ dan varietas Bonita, dan penurunan penyebaran gemini virus (Geminiviradae) pada 4 MSJ dibandingkan kontrol. Penggunaan waktu tanam yang sesuai dengan kombinasi varietas yang tepat dapat meningkatan nilai produktifitas serta menekan penyebaran penyakit tanaman dan dapat menjadi salah satu upaya untuk menerapkan pertanian berkelanjutan berbasis ramah lingkungan dan meningkatan penghasilan petani., Cayenne pepper (Capsicum frutescens L.) is a high economic value horticultural crop. In chili cultivation, land conversion leads to a decrease in the area under cultivation. One way to overcome this problem is to use intercropping on land under tree stands or to plant chili on land planted with maize. Finding a precise planting time and suitable varieties in intercropping patterns is the purpose of this study. This research utilized a nested design with two treatment factors, namely planting time with four levels: control (cayenne pepper monoculture), 0, 4, and 6 weeks after maize planting (MSJ) as the main plot and chili varieties, namely Bonita, Shadiva and Lobita as subplots. The research implementation includes sowing, soil preparation, planting, maintenance, and harvesting. The results of this study indicate a significant influence of planting time at 0 MSJ on the increase in plant height, particularly in the Shadiva variety, and suggest the possibility of etiolation resulting from prolonged shading periods compared to other planting times. The results indicated that the Bonita variety exhibited higher productivity values at the 4 MSJ planting time. In contrast, the control exhibited a higher incidence of the Gemini virus (Geminiviridae) at the same planting time. The optimal selection of planting time, in conjunction with the most suitable varieties, can enhance productivity and suppress the spread of plant diseases, thereby promoting sustainable agricultural practices that are environmentally friendly and increasing farmers' income.
Keyword: agroforestry, geminivirus, smart farming, sustainability, shading

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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