Judul: Potensi Aspergillus dan Penicillium asal serasah dipterocarp sebagai endosimbion akar pelarut fosfat
Abstrak: The ability of soil microorganisms especially fungi to convert insoluble forms of phosphorus (P) to an accecible form is important for plant growth and development. Aspergillus sp. IPBCC.09.619 and Penicillium sp. IPBCC.09.620 showed phosphate solubilizing capacity in vitro. However, phosphate solubilizer capability and its endosymbiotic capacity with Zea mays and Shorea selanica root have not been studied. This study was aimed to evaluate the potency of Aspergillus and Penicillium from dipterocarp leaf litter as phosphate solubilizer and root endosymbiont. Microscopic observations of Z. mays and S. selanica seedlings before fungal inoculation showed that Z. mays roots were free from endosymbiotic fungi while those of S. selanica bore Dark Septate Endophyte (DSE). DSE occurred on 85% of S. selanica root seedlings and it is assumed that DSE has synergetic function with Penicillium sp. Of the two fungi studied, only Penicillium sp. lives as endosymbiont. Colonization of Penicillium sp. to Z. mays and S. selanica roots started at root hairs and then penetrated epidermal cell through epidermal junction. Some hyphae became lobed within epidermal and cortical cells and fullfiled inoculated cells with tiny hyphae. After 8 weeks inoculation, hyphae came out from the epidermal cells and developed penicillate structure on root surface. Inoculation of Penicillium sp. to Z. mays root at 100% TCP dosage (equal to 60 mg P2O5/plant) increased all of growth parameters, except S. selanica shoot length. Shoot dry weight of Z. mays and S. selanica showed higest response to fungal inoculation as indicated by 82% and 54.7% increases respectively. Colonization of Penicillium sp. to both plants increased P uptake at 60 mg P2O5 /plant dosage (37% and 103% higher than plant control respectively). Phosphorus uptake at 50% P dosage was not significantly different with control. It means, inoculation of Penicillium sp. makes application of P efficient.
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Judul: Potensi Aspergillus niger dan Penicillium spp. sebagai Endosimbion Pelarut Fosfat pada Akar Serealia
Abstrak: Aspergillus niger and Penicillium sp. are known to have the ability to solubilize phosphorus (P). P in acid soils exists in unavailable forms that decrease productivity. Indonesia has a large acid soil that used for cereal crops production. Therefore, the potential of A. niger (IPBCC 10.643) and Penicillium spp. (IPBCC 09.620 and 09.621 IPBCC) as P solubilizing endosymbiont in the roots of cereals (maize, sorghum, and rice) was studied. Endosymbiosis of P solubilizing fungi was observed in germlings that were free from endophytic fungi and planted on zeolite in acidic condition with AlPO4 as a source of P, for eight weeks period. Endosymbiosis was determined based on fungal percentage of colonization in the roots. The effects of endosymbiosis on plant growth was measured as height and dry weight of plants for four weeks, and also by efficiency of nutrient uptake in plants at eight weeks old. The results of this study indicated that A. niger and Penicillium spp. colonized the roots up to 70%, so the fungi were considered as endosymbionts. Association of A. niger and roots showed a negative effect on all test plants. Two strains of Penicillium spp. only increased the height and dry weight of sorghum and increased P uptake in maize and sorghum. The N, P, and K efficiency uptake of maize that inoculated with Peniclillium sp. IPBCC 09.620 about 1.22, 1.45, and 1.36 of the control respectively, while those inoculated with Penicillium sp. IPBCC 09.621 were 1.55, 1.52, and 1.04, respectively. Sorghum that were inoculated with Penicillium sp. IPBCC 09.620 showed the efficiency uptake of N, P, and K about 1.04, 2.00, and 1.79, respectively. This efficiency uptake of N, P, and K as relatively greater than the efficiency uptake of N, P, and K of sorghum plants (1.19, 1.30, and 1.46, respectively) that were inoculated Penicillium sp. IPBCC 09.62
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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. ,,,
Keyword: graf Hamilton, graf regular, graf lengkap, graf 2-connected 4-regular.