We aimed to explore the effects of different concentrations, in particular, high concentrations, of exogenously applied ethephon and methyl jasmonate on gum duct formation in three broad-leaved tree species, Cerasus × yedoensis, Prunus mume and Liquidambar styraciflua. Intact shoots were treated with ethephon and methyl jasmonate in lanolin paste at concentrations of 0.1%, 1%, 2%, 5%, and 10% (w/w). The ethephon treatments induced gum duct formation in the xylem adjacent to the cambium in all three species, whereas the methyl jasmonate treatments did not. The highest induction of gum duct formation was observed after 1–2% ethephon treatments in C. × yedoensis and P. mume, and after 5–10% ethephon treatments in L. styraciflua. Meanwhile, the treatments with higher ethephon concentrations resulted in a lower induction of gum duct formation in C. × yedoensis and P. mume. In addition, we examined gum duct formation at sites distant from the treatment sites in C. × yedoensis and P. mume shoots treated with 10% ethephon. Gum duct formation was found to be the highest at sites 2 cm away from the treatment site (in the acropetal direction). We show that at least in C. × yedoensis and P. mume, trees have an optimal concentration of ethephon to induce gum duct formation, and that concentrations higher than the optimum suppress the induction.

Abstrak: Asam sitrat terdapat melimpah di alam dan dihasilkan sebagai salah satu zat antara pada siklus asam sitrat saat karbohidrat dioksidasi menjadi karbondioksida. Asam sitrat merupakan penyebab rasa asam pada berbagai buah seperti jeruk, nanas dan pir. Karena kelarutannya yang tinggi, rasanya yang enak dan toksisitasnya yang rendah maka asam sitrat banyak digunakan dalam industri makanan, minuman dan obatobatan. Salah satu metode yang digunakan untuk produksi asam sitrat adalah dengan metode fermentasi. Aspergilus niger merupakan salah satu mikroorganisme yang dapat digunakan pada proses produksi asam sitrat. Produksi asam sitrat pada penelitian ini dilakukan dengan tahap pemeliharaan A. niger pada media agar miring, aktivasi kultur A. niger dalam inokulum dan produksi asam sitrat dalam media fermentasi yang mengandung 20, 25, 30 dan 35% konsentrasi molase dengan metode biak rendam. Analisis yang dilakukan mencakup perubahan pH, berat kering sel, konsumsi gula pereduksi, serta konsentrasi asam sitrat yang dihasilkan. Hasil penelitian ini menunjukkan bahwa asam sitrat paling banyak diproduksi pada media yang mengandung 30% molase, yaitu diperoleh 85,8 g/L asam sitrat. Kata kunci: Aspergillus niger, asam sitrat, molase Abstract: Citric acid.is naturally present in nature as one of intermediate in citric acid cycle when carbohydrate oxidized to carbondioxide. It is responsible for sour taste in oranges, pineapples, and pear. Because of its high solubility, tasty taste, and very low toxicity, citric acid is widely used in foods, beverages, and medicines industries. One of methods than can be used for citric acid production is fermentation and A. niger is one of the

The aim of this research was to examine the larvicidal activity of essential oil (EO) extracted from nutmeg (Myristica fragrans Houtt) leaves and fruits by steam distillation, and to analyze its chemical compounds. The EO yield of nutmeg leaves and fruits collected from the same tree was 0.66% and 0.30%, respectively. Larvicidal tests with the EO were carried out against Aedes aegypti (L.) (Diptera: Culicidae). The concentrations of nutmeg EO used for the larvicidal assay were 50, 100, 150, 200, and 250 μg/mL. The results showed that fruit oil was more toxic than the leaf oil. LC50 values of leaf and fruit EOs were 133.8 and 110.1 µg/mL, respectively. The chromatogram of GC-MS showed that the chemical components in nutmeg leaf and fruit EOs were dominated by α-pinene, sabinene, β-pinene, delta-3-carene, limonene, β-phellandrene, α-terpinolene, linalool, safrole, croweacin, and myristicin.

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