Judul: Potensi kapang asal serasah tanaman hutan sebagai penghasil asam indol asetat dan toleransinya terhadap kondisi asam
Abstrak: Microorganism in soil and forest litter plays an important role in maintaining the health of the soil such as decomposer, nutrient transformation agent, mineral solubilizer, and also as hormones producer. One of the hormones produced by microorganism including molds is indole-3-acetic acid (IAA). Utilization of IAA producer molds that tolerance to acid conditions may increase the production of industrial forest in acid soil and improve the vigour of plantling stock material originated from stem cutting. This study was aimed to assess the potential of forest litter molds of IPBCC (Institut Pertanian Bogor Culture Collection) collection as IAA producers and their tolerance to acid conditions. The ability of fifty-one forest litter molds from Katingan and Tarakan to produce IAA was screened in Czapek Dox medium and was determined by Patten and Glick method using Salkowski reagent. According to Patten and Glick method, the forest litter molds from Katingan produced IAA (1.92±0.26 ppm) were higher than those of Tarakan (1.08 ± 0.14 ppm). The production of IAA by static incubation (2.72±0.89 ppm) was higher than those of shaking incubation (1.92 ± 0.26 ppm). The production of IAA on the forest litter molds from Katingan (63.16%) were not influenced by the storage process. Four out of fifty Katingan’s molds were selected for IAA production, those were Acremonium sp. IPBCC 07.548 (3.52±0.46 ppm), Aspergillus ornatus IPBCC 07.554 (4.50±0.92 ppm), Gliocladium deliquescens IPBCC 07.543 (2.23±0.38 ppm), and Penicillium notatum IPBCC 07.555 (5.06±0.46 ppm). IAA and its biomass productions were influenced by pH of the medium. These forest litter molds were considered to be acid tolerance. The pH optimum for their growth and IAA production were 5.5. These molds showed no antagonistic response to each other. The IAA production from these molds in consortium (7.22±1.33 ppm) were better than its single culture (4.43±1.53 ppm). High performance liquid chromatography assay indicated that there was only one type of IAA with retention time 7.1.
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Judul: Isolation and selection of nitrogen-fixing and producing indole-3-acetic acid bacteria from soil samples of Jambi Indonesia
Abstrak: Mikrob yang terdapat di dalam tanah memainkan peranan penting dalam produktivitas tanaman, terutama dalam proses penambatan nitrogen bebas di alam dan menghasilkan substansi zat pemacu tumbuh seperti Indole-3-Acetic Acid (IAA) eksogen. Kedua ciri tersebut diperlukan untuk memacu pertumbuhan tanaman. Penelitian ini bertujuan mengisolasi dan menyeleksi bakteri penambat nitrogen dan penghasil IAA asal sampel tanah di Taman Nasional Bukit Dua Belas (TNBD) Jambi. Isolasi dilakukan pada 17 sampel tanah yang diambil dari daerah rhizosfer tanaman kelapa sawit. Media yang digunakan untuk isolasi ialah media semisolid Nitrogen Free Bromthymol Blue (NfB). Isolat yang dipilih merupakan isolat yang dapat membentuk pelikel berwarna putih pada permukaan media semisolid tersebut dan mampu mengubah warna media dari hijau menjadi biru karena terjadi peningkatan pH. Isolasi menghasilkan sepuluh isolat terpilih yang kemudian diidentifikasi morfologinya. Identifikasi morfologi koloni dan sel menghasilkan lima isolat. Isolat yang menunjukkan pertumbuhan yang baik yaitu isolat A13.1 yang diidentifikasi sebagai Pseudomonas luteola dengan menggunakan KIT API 20 NE. Isolat A13.1 menghasilkan IAA eksogen tertinggi pada waktu inkubasi hari ke-5 di media NfB. Konsentrasi IAA yang terukur sebesar 33,88 ppm. Kata kunci: IAA (Indole-3-Acetic Acid), mikrob, nitrogen, Nitrogen Free Bromthymol Blue (NfB), rhizosfer, Soil microbes plays an important role in crop productivity, especially in the process of nitrogen fixation in free nature and produces growth promoting hormone substances such as Indole-3-Acetic Acid (IAA) exogenous. Both of these character are needed to promote of plant growth. This study aimed to isolate and select nitrogen-fixing and producing IAA bacteria from soil samples in Taman Nasional Bukit Dua Belas (TNBD) Jambi. Isolation was performed in 17 soil samples taken from the area of oil palm plant rhizosphere. The medium used for the isolation of semisolid medium is Nitrogen Free Bromthymol Blue (NFB). Isolates were selected to form an isolated white pellicle on the surface of the semisolid media and the media is able to change color from green to blue due to increase of pH. Isolation produced ten selected isolates were then identified its morphology. Identification of colony morphology and cell produces five selected isolates. Isolate A13.1 showed the best growth and identified as Pseudomonas luteola using KIT API 20 NE. The.isolate produced maximum exogenous IAA at 5 days incubation at medium NfB. The amount of IAA was 33.88 ppm. Keywords: IAA (Indole-3-Acetic Acid), microbes, nitrogen, Nitrogen Free Bromthymol Blue (NfB), rhizosfer
Keyword: IAA (Indole-3-Acetic Acid), mikrob, nitrogen, Nitrogen Free Bromthymol Blue (NfB), rhizosfer

Judul: Cycle Hamilton pada Graf Lengkap, Graf Regular, dan Graf 2-Connected 4-Regular Berorder Kurang dari Sepuluh
Abstrak: Suatu graf disebut graf Hamilton apabila graf tersebut memuat cycle Hamilton, yaitu cycle yang melewati setiap vertex tepat satu kali. Menentukan keberadaan cycle Hamilton pada suatu graf dapat menggunakan syarat cukup yang berupa teorema-teorema yang telah diperkenalkan sejak tahun 1950-an. Beberapa syarat cukup yang dibahas dalam karya ilmiah ini adalah syarat cukup yang berhubungan dengan graf lengkap dan graf regular. Suatu graf lengkap berorder 𝑛������ ≥ 3 dan graf r-regular berorder 𝑛������ ≤ 2𝑟������ + 1 merupakan graf Hamilton, Karena kedua graf tersebut memuat cycle Hamilton. Selanjutnya, syarat cukup tersebut digunakan untuk menentukan keberadaan cycle Hamilton pada graf 2-connected 4- regular berorder kurang dari 10.
Keyword: graf Hamilton, graf regular, graf lengkap, graf 2-connected 4-regular