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: The Potential of Forest Litter Penicillium and Trichoderma on IAA Production in Meranti Leaves Compost
Abstrak: Environmental manipulation through utilization of forest litter combined with microbial inhabiting rhizosphere is applied to achieve sustainable, prospective and healthy meranti (Shorea spp.) forest. Penicillium IPBCC 09 622 (SI1) and Trichoderma IPBCC 09 620 (SI2) originated from Dipterocarp litter were known to be able to reduce C/N ratio of Dipterocarp litter as well as produce IAA (Indole-3-Acetic Acid) in vitro. This study is aiming to assess the potential of these two fungi as a single (SI1, SI2) or their consortium (SI3) inoculants in producing IAA in meranti leaves compost. The compost was consisted of a mixture of meranti leave litter (83%), rice bran (15%) and urea (2%) at 60% moisture content. About 100 g of this mixture were placed in each polybag and steamed at 104oC for 30 minutes. The mixture were then inoculated with fungal biomass (SI1, SI2, or SI3) and then kept for 4 months. Uninoculated compost (SI-), steamed compost containing 4 ppm IAA synthetic (SA), and unsteamed and uninoculated compost (S-I-) were used as control. Each treatment had 3 replications. Observation was done monthly on population of Penicillium and Trichoderma, C/N ratio, water content (WC), organoleptic (color, texture and smell) and temperature (t) of the compost. At the end of decomposting period, minerals P, K, Ca and Mg, weight loss, decomposition rate analyses and bio-assay using shoot cutting of meranti tembaga (Shorea leprosula) were done. Observation indicated that Penicillium did not survive, but Trichoderma survived throughtout decomposition period. Penicillium did not have lignases, while Trichoderma only had tyrosinase. Fungal contamination occured during composting periods in all compost. About 10 fungal species were isolated in which Trichoderma was dominant. This contamination might effect to the overall research result. C/N ratio, WC and t content fluctuated between 15.93-45.47, 12.88-67.31% and 26-30.33oC respectively. At the end of composting period, C/N ratio was 15.93-18.53, WC was 26.55-50.94%, t was 29.67-30.33oC and minerals (P, K, Ca and Mg) content were 0.27-0.39%, 0.32-2.58%, 0.67-1.34%, 0.26-0.94%, respectively. Weight loss and decomposition rates was low, approximately 2.33-10.67% and 0.0058-0.028/yr respectively. The color, texture and smell of the compost did not meet the criteria SNI no. 19-7030-2004, while the C/N ratio and WC met SNI criteria. IAA production more were higher if the compost were inoculated with Trichoderma or it was infested by Trichoderma. IAA varied betwen 0.17-10.91 ppm depending on treatments. IAA detected using HPLC (high performance liquid chromatography) was slightly lower than those obtained from Salkowsky reagent. At the end of the composting, the compost was mixed with sterilized soil (1:1) and used for planting media of stem cutting. Bio-assay indicated that only 0.00-13.33% shoot cuttings of meranti tembaga showed root initiation depending on the composts. In conclusion Penicillium was not a potential agent, but Trichoderma was potential for IAA production in meranti leaves litter compost.
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Judul: Closed Knight’s Tour pada Papan Catur Berbentuk Persegi Panjang dengan Ukuran Maksimal 8 × 8
Abstrak: Closed Knight’s Tour merupakan langkah kuda yang mengunjungi setiap kotak pada papan catur tepat satu kali dengan langkah kuda berawal dan berakhir pada kotak yang sama. Graf yang terbentuk dari closed knight’s tour dinotasikan sebagai graf G(m,n), dengan m adalah banyaknya baris dan n adalah banyaknya kolom. Graf tersebut memuat Hamiltonian cycle. Sebuah graf terhubung G adalah graf bipartite jika dan hanya jika graf tersebut tidak memiliki cycle dengan panjang ganjil. Papan catur yang memenuhi syarat cukup untuk memiliki closed knight’s tour adalah papan catur berukuran 5 × 6, 5 × 8, 6 × 6, 6 × 7, 6 × 8, 7 × 8, dan 8 × 8.
Keyword: bipartite, closed knight’s tour, hamiltonian cycle, knight’s tour, teori graf