Judul: Evaluation of Silica Uptake from Foliar-Applied Silicon Nanoparticles in Melon (Cucumis melo L.) under Soilless Culture
Abstrak: Melon (Cucumis melo L.) is one of the fruit commodities which get a great interest to be developed in Indonesia and has a high nutritional value. However, the fungal infection and pathogens in melon cultivation are considered significant problems that are difficult to manage. Therefore, efforts are needed to improve the productivity and quality of melon and prevent pest and disease attacks. One mineral nutrient that is assumed to enhance plant resistance and increase the quality and production of melon is silica. The purpose of the research was to evaluate silica absorption from foliarapplied silicon nanoparticles in melon under soilless culture and improve melon fruit's growth and quality by applying silica fertilizer. This experiment was conducted in the greenhouse at IPB University, Leuwikopo experimental station (Indonesia), from February to May 2021. The experimental design used in this study was a splitplot randomized complete block design 3 x 2 factorial pattern with four replicates, i.e., by adding silica fertilizer and using two varieties of melon. The main plot factor is applying silica fertilizer (Novelgro, water-soluble), consisting of 3 silica concentrations, namely 0.67; 1.33 ppm, and control (without silica). The subplot factor is melon varieties consisting of Alisha and Glamour. Experimental data were analyzed using analysis of variance and followed by Duncan's Multiple Range Test (DMRT) if there is a significant effect. The findings showed that the foliar application of silica fertilizer significantly increased the plant height, stem diameter, internode length, total number of hermaphrodite flowers, number of hermaphrodite flowers that are swelling, while decreased the fruit moisture content and gave the best average fruit position. Instead, melon cultivars produced in soilless culture differed substantially in terms of growth rate and fruit quality. Glamour cultivars' growth rate and fruit quality increased significantly regarding plant height, stem diameter, internode length, leaf area, fruit weight, fruit diameter, fruit length, total soluble solids, flesh thickness, and rind thickness, while decreased number of fallen hermaphrodite flowers. In contrast, the Alisha cultivar gave a better growth rate regarding the number of leaves, the total number of hermaphrodite flowers, and the number of swollen hermaphrodite flowers. However, the results of this study did not show any interaction between treatments on the experimental parameters. Moreover, our study indicated that the melon plant could absorb silica in the low category (<1% Si). The highest silica contents were found in the Alisha cultivar leaves and the Glamour cultivar's rinds treated with the silica concentration of 1.33 ppm as much as 0.34% and 0.30%, respectively.
Keyword: crispness, drip irrigation, fertigation, silica absorption efficiency

Judul: Respon Pertumbuhan dan Kualitas Buah Melon (Cucumis melo L.) Hidroponik terhadap Aplikasi Nano Silika melalui Daun.
Abstrak: Melon (Cucumis melo L.) merupakan salah satu tanaman yang menjadi komoditas unggulan agribisnis Indonesia. Inovasi yang dapat diterapkan dalam teknik budidaya tanaman melon adalah hidroponik. Sistem hidroponik yang digunakan tanaman melon adalah teknologi hidroponik sistem substrat dengan pemberian larutan hara melalui irigasi tetes (drip irrigation). Salah satu upaya untuk meningkatkan kualitas dan produktivitas melon serta meningkatkan daya tahan tanaman dapat dilakukan penambahan unsur silika. Silika (Si) dikenal sebagai unsur hara bermanfaat. Meskipun syarat sebagai unsur hara esensial belum terpenuhi, namun unsur Si telah lama diketahui sebagai unsur penting bagi beberapa tanaman. Penelitian ini bertujuan untuk mengetahui respon tanaman melon hidroponik terhadap aplikasi nano silika melalui daun. Rancangan yang digunakan adalah rancangan acak lengkap (RAL) faktor tunggal. Perlakuan pada percobaan ini adalah peningkatan konsentrasi nano silika dari konsentrasi yang direkomendasikan sebanyak 5 taraf yaitu 0.00, 0.75, 1.50, 2.25, dan 3.00 ml/liter air, dengan 4 ulangan. Setiap satuan percobaan terdiri dari 2 tanaman yang diamati sehingga terdapat 40 tanaman contoh. Pengamatan yang dilakukan meliputi tinggi tanaman, jumlah daun, jumlah ruas, diameter batang, bunga jantan, bunga betina, bunga betina rontok, bobot buah, diameter buah, tebal daging buah, dan kemanisan. Hasil percobaan menunjukan bahwa aplikasi nano silika pada tanaman melon tidak berpengaruh nyata terhadap pertumbuhan tanaman dan kualitas buah melon, kecuali jumlah bunga betina yang rontok pada umur 3 MST. Terdapat korelasi positif antara tinggi ruas dengan ukuran buah melon.
Keyword: hidroponik, irigasi tetes, silika

Judul: Bifurkasi Hopf pada Model Siklus Bisnis Kaldor Kalecki tanpa dan dengan Waktu Tunda
Abstrak: Business cycle model is one of dynamical system models in economic. One of the business cycles model is Kaldor-Kalecki model. Kaldor-Kalecki business cycle model that is written in delayed defferential equations, is a business cycle model that involves gross product and capital stock of a company. In this paper Kaldor-Kalecki business cycle model is analyzed using both nondelay and delay in time of capital stock. By Taylor expansion for the time delayed model, an analysis of stability around the fixed points has been done. Furthermore, by using Hopf bifurcation theorem, it can be shown that there exists periodic orbits and limit cycle. In the nondelayed model, changing the parameter of goods market could lead to the occurrence of Hopf bifurcation and the existence of limit cycle. Similarly, for the delayed model, it has been shown that changing the time delay parameter may result in the occurrence of Hopf bifurcation and limit cycle.
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