Judul: Study on Flower Phenology of Hydrangea (Hydrangea macrophylla)
Abstrak: Hydrangea (Hydrangea macrophylla) is commonly utilized as ornamental plant, both as cut flower and garden component. Study on flower phenology is necessary in hydrangea development as cut flower, one of which to determine the proper flower harvest time. The objective of this study was to observe flower phenology of hydrangea. This research was conducted on December 2019 to February 2020 at Ciloto Village, West Java. Serial observation on inflorescences and florets of nine sample flowers from nine sample plants was conducted for 69 days after flower initiation (DAFI). The observation results showed that the development of decorative flower of H. macrophylla can be divided into five stages. Number of florets at particular stage determines the overall appearance and size of the inflorescence. Inflorescence at 1 DAFI was composed of florets at stage 1. Total floret per inflorescence increased over time with the highest average of total floret per inflorescence at 22-29 DAFI, dominated by floret at stage 2. Total floret per inflorescence decreased at 36 DAFI due to some fallen florets. Floret at stage 5 started dominating at 43 DAFI and no florets at 1-4 stages can be observed at 50-57 HSI. Despite the highest average of total floret per inflorescence observed at 22-29 DAFI, the maximum inflorescence size was observed at 50-57 DAFI. Commercial harvest stage, defined as approximately 80% of the decorative florets in the inflorescence had developed the cultivar specific color, was observed at 43 DAFI., Hydrangea (Hydrangea macrophylla) merupakan tanaman yang dapat dimanfaatkan sebagai tanaman hias, baik sebagai bunga potong maupun komponen taman. Informasi terkait fase perkembangan bunga (fenologi) diperlukan dalam pengembangan hydrangea sebagai tanaman hias, salah satunya untuk menentukan waktu panen bunga yang tepat. Penelititan ini bertujuan untuk memperoleh informasi terkait perkembangan bunga hydrangea. Penelitian dilaksanakan pada bulan Desember 2019 sampai Februari 2020 di Desa Ciloto, Jawa Barat. Pengamatan serial terhadap bunga majemuk (inforescence) dan bunga tunggal (floret) dilakukan terhadap sembilan bunga dari sembilan tanaman contoh selama 69 hari setelah inisiasi (HSI) bunga. Hasil pengamatan menunjukkan stadia perkembangan floret dekoratif H. macrophylla dapat dibagi ke dalam lima stadia, dengan floret kuncup ditentukan sebagai stadia 1 dan floret mekar sempurna ditentukan sebagai stadia 5. Jumlah floret pada stadia tertentu menentukan tampilan dan ukuran inflorescence secara keseluruhan. Inflorescence pada 1 HSI seluruhnya terdiri atas floret pada stadia 1. Total floret per inflorescence meningkat seiring bertambahnya waktu, dengan rata-rata total floret per inflorescence tertinggi pada 22-29 HSI yang didominasi oleh floret pada stadia 2. Jumlah total floret per inflorescence mulai menurun pada 36 HSI karena adanya floret yang gugur. Floret pada stadia 5 mulai mendominasi pada 43 HSI dan tidak ada lagi floret pada stadia 1-4 yang terobservasi pada 50-57 HSI. Stadia panen komersial pada penelitian ini dicapai pada 43 HSI.
Keyword: floret, flower, inflorescence, phenology, cut flower

Judul: Cultivation, Harvest, and Postharvest of Hortensia Cut Flower (Hydrangea macrophylla) at Kwekerij Figaro B.V., Naaldwijk, South Holland
Abstrak: H. macrophylla merupakan bunga potong yang populer di pasar Eropa karena keindahannya. Vase life menjadi penentu bagi keputusan konsumen dalam membeli bunga potong karena pendeknya vase life dapat menurunkan kepuasan konsumen dan mengurangi nilai estetikanya. Kegiatan magang bertujuan meneliti lebih lanjut proses budidaya H. macrophylla di Kwekerij Figaro B.V. serta mendapatkan informasi mengenai konsentrasi larutan perendam yang tepat untuk mendapatkan vase life H. macrophylla ‘Mammoet’ yang optimum. Proses budidaya yang diamati meliputi kondisi greenhouse, irigasi, pemupukan, pengendalian OPT, produksi, dan pemasaran. Produksi dan penjualan H. macrophylla ‘Mammoet’ mengalami penurunan yang signifikan di periode 2021–2023 dikarenakan masalah pada sistem pengairan yang perlu diperbaiki di periode budidaya berikutnya. Penelitian larutan perendam vase life menggunakan RKLT faktorial dua faktor, yakni larutan Chrysal Grow 20 dan Vaselife Universal Flower Food. Vase life dengan hari paling panjang dan efisien terdapat pada konsentrasi 8 mL L-1 Chrysal Grow 20. Penambahan Vaselife Universal Flower Food 1 mL L-1 pada bunga membuat vase life terpanjang, yakni 9,18 hari, lebih panjang 1,95 hari dibanding perlakuan air (kontrol). Interaksi antar dua larutan menunjukkan hasil yang tidak nyata., H. macrophylla is a popular cut flower in the European market due to its aesthetics. Vase life is a determining factor for consumer decisions when purchasing cut flowers because a short vase life can reduce consumer satisfaction and diminish its aesthetic value. The internship activity aims to further investigate the cultivation process of H. macrophylla at Kwekerij Figaro B.V. and obtain information about the appropriate vase life solution dosage to achieve optimal vase life for H. macrophylla 'Mammoet'. The observed cultivation process includes greenhouse conditions, irrigation, fertilization, pest and disease control, production, and marketing. The production and sales of H. macrophylla 'Mammoet' experienced a significant decline in the period 2021–2023 due to issues with the irrigation system that need to be addressed in the subsequent cultivation periods. The study on vase life solutions used a two-factor RCB design, namely Chrysal Grow 20 and Vaselife Universal Flower Food solutions. The longest and most efficient vase life solution was found at a concentration of 8 mL L-1 Chrysal Grow 20. The addition of 1 mL L-1 Vaselife Universal Flower Food resulted in the longest vase life, which is 9.18 days or 1.95 days longer than the water treatment (control). The interaction between the two solutions showed statistically insignificant results.
Keyword: cultivation, greenhouse, hydrangea, vase life

Judul: Metrik Einstein (Anti-) Self-Dual Berdimensi Empat dengan Metode Cartan
Abstrak: Gravitational field equation can be formulated in differential forms (differential geometry), which describes gravity as a manifestation of the curvature of space-time. Curvature of space-time is characterized by a metric that satisfies the gravitational field equation. With differential forms it can be formulated the (anti-) self-dual Einstein equation, which is a modification of the Cartan structure in (anti-) self-dual basis. Calculation of (anti-) self-dual metric with (anti-) self-dual Einstein equation is simpler than the calculation using Christoffel symbols.
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