Judul: Penggunaan Mycorrhizal helper bacteria (MHBs) dan fungi mikoriza arbuskula (FMA) untuk meningkatkan pertumbuhan semai mindi [Melia azedarach Linn]
Abstrak: Laju degradasi kawasan hutan di Indonesia masih tinggi, yang menyebabkan semakin berkurangnya luas hutan dan meningkatnya luas lahan kritis. Dalam upaya untuk mengurangi dampak yang ditimbulkan dari kerusakan hutan tersebut, dilakukan kegiatan rehabilitasi hutan dan lahan. Namun yang menjadi kendala utama bagi keberhasilan kegiatan rehabilitasi adalah terhambatnya pertumbuhan semai dan semai memiliki daya hidup yang rendah. Untuk mengatasi masalah tersebut diperlukan bibit yang berkualitas baik dan dapat bertahan hidup pada tanah-tanah marginal. Namun untuk mendapatkan bibit yang berkualitas baik dan memiliki daya hidup yang tinggi dilapangan diperlukan input hara yang cukup, yaitu dengan pemberian pupuk. Pupuk yang diberikan haruslah aman bagi lingkungan dan sesuai dengan ekosistem. Penggunaan teknologi mikroba tanah yaitu dengan penggunaan mikoriza merupakan solusi yang tepat dan telah terbukti mampu meningkatkan pertumbuhan tanaman. Salah satu fungi mikoriza yang telah dikenal dapat dijadikan pupuk hayati (biofertilizer) adalah FMA (Fungi Mikoriza Arbuskular). Simbiosis antara fungi dengan perakaran tanaman, dalam perkembangannya dilapangan seringkali mengalami kendala. Untuk itu diperlukan mikroorganisme yang dapat memberikan pengaruh positif terhadap peningkatan kerjasama tersebut, yaitu jenis bakteri yang dikenal dengan nama Mycorrhizal Helper Bacteria (MHBs). MHBs merupakan bakteri spesifik yang dapat bersimbiosis dengan FMA dan mempunyai kemampuan untuk menstimulir perkembangan FMA. Dengan aplikasi MHBs dan FMA pada mindi diharapkan dapat meningkatkan pertumbuhan dan kualitas hidup semai mindi. Penelitian ini dilaksanakan di laboratorium dan Rumah Kaca Departemen Silvikultur, Fakultas Kehutanan Institut Pertanian Bogor. Pelaksanaan penelitian diawali dengan isolasi spora mikoriza, dimana isolasi spora tersebut dilakukan melalui teknik penyaringan basah bertingkat dan dilanjutkan dengan metode sukrosa sentrifugasi menurut Jenkins (1964). Selanjutnya spora Glomus sp dan Gigaspora sp yang sudah dipilih kemudian disimpan dalam refrigerator sampai digunakan. Tahapan penelitian selanjutnya adalah persiapan tanaman inang (tanaman mindi) serta perbanyakan dan pembuatan larutan isolat bakteri. Persiapan tanaman mindi yang dimaksud adalah perkecambahan benih mindi yang diawali dengan perlakuan pendahuluan dengan menjemur benih mindi dibawah sinar matahari selama 1 minggu sampai kulit bijinya menjadi retak. Inokulasi FMA dan bakteri dilakukan pada saat penyapihan sesuai dengan perlakuan yang diberikan. ...
Keyword: AMF, MHBs, Mindi

Judul: Pemanfaatan Mycorrhizal Helper Bacteria (MHBs) dan Fungi Mikoriza Arbuskula (FMA) untuk Meningkatkan Pertumbuhan Semai Gmelina (Gmelina arborea Roxb.)
Abstrak: INTRODUCTION. Increase in the size of human population causes an ever increasing demand on paper produtcs. Therefore, there is a need to supply wood as raw materials in rapid manner. In relation with this, the Indonesian government has a policy to develop Industrial Plantation Forest (HTI). Gmelina is one of the forest tree species which has good prospect to be developed in Industrial Plantation Forest (HTI). This species is a fast growing species which could grow in various types of soil, and its wood is considerably useful. Development ofHTI in Indonesia is emphasized on critical land. The use of Arbuscular Mycorrhizal Fungi (AM F) is an appropriate solution for promoting plant growth in such condition. In the field, AMF had some constraints in creating symbiosis with host plants, Therefore, in this case, there is a need for bacteria which stimulates the AMF. One such bacteria, is known with the name Mycorrhizal Helper Bacteria (MHBs). MATERIALS AND METHOD. This research used Factorial Completely Randomized Design comprising 16 treatments, 5 replications and 3 units. Inoculation of mycorrhizal fungi and bacteria was conducted when the seedlings were 3 weeks old. Afterwards, observation was conducted for 3 months. For observing the plant's respond toward treatments, the observed parameters were among other things: height, diameter, root biomass, shoot biomass, shoot - root ratio, Index of Seedling Quality, and percentage of mycorrhizal infection. RESULTS AND CONCLUSION. Results of Analysis of Variance showed that mycorrhizal treatment had significant effect on parameters of root biomass and percentage of mycorrhizal infection. On the other hand, combined treatments of mycorrhiza and bacteria had significant effect toward parameter of root biomass. Combination of mycorrhiza with isolate BGLo3 gave the highest percentage of mycorrhizal infection, namely 25.49 %. Inoculation of isolate BGLo1 gave the best respond for parameters of height and diameter. Consecutively, the exhibited increases were 32.33 % and 31.25 % as compared with those of control. Combination of mycorrhiza with BGLo3 also exhibited the highest increase as compared with control, in terms of parameters of root biomass and Index of Seedling Quality, namely 2.28 % and 87.89 %. Inoculation ofmycorrhiza without bacteria exhibited the best respond for parameters of shoot - root ratio, namely with increase by 9.23 % as compared to control.
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Judul: Truncated Stop Loss as a Optimal Solution of Reinsurance Agreement in One-Period Model
Abstrak: Reinsurance is one of risk management efforts of an insurance company, which is called the cedent. Similar with insurance, reinsurance constitutes the cedent to pay the premium. We consider one-period reinsurance model and derive a rule which minimizes the ruin probability of the cedent for a fixed reinsurance premium. Therefore, it is needed to construct an optimal reinsurance agreement for the cedent. The premium is calculated according to four different principles, i.e. economic, generalized zero-utility, Esscher, and mean-variance principles. Stop loss is a reinsurance contract which protect the insurance company for losses that exceed a certain amount. The result of this research shows that a truncated stop loss is an optimal agreement in the class of all reinsurance contracts with various premiums calculated using above mentioned principles.
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