Judul: Induksi keragaman Somaklon ke arah ketenggangan terhadap keracunan aluminium pada tanaman jagung
Abstrak: Masalah keracunan aluminium merupakan faktor pembatas utama bagi pertumbuhan dan produksi tanaman pada tanah masam. Diperkirakan total luas areal tanah masam di Indonesia sekitar 101.5 19 juta hektar, 48.3 j uta hektar diantaranya merupakan jenis podzolik merah kuning. Dalam rangka rnencapai swasembada jagung di masa mendatang, maka upaya peningkatan produktivitas dan pengembangan lahan-lahan marjinal perlu terus digalakkan. Oleh karena itu, tersedianya varietas-varietas jagung yang tenggang tethadap keracunan A1 sangat diperlukan.
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Judul: Fitotoksisitas aluminium pada jagung hibrida ipb-4 dan H-6
Abstrak: Ketahanan varietas jagung terhadap keracunan Al, khususnya varietas-varietas yang dikembangkan di Indonesia, belum banyak diteliti. Ketoleranan terhadap Al merupakan sifat yang perlu dipertimbangkan dalam usaha mencapai hasil yang maksimum. Tujuan penelitian ini yaitu mempelajari pengaruh ber- bagai tingkat kejenuhan Al terhadap (1) respon pertumbuhan dan produksi bahan kering, (2) kadar dan serapan Al, Ca and Mg jagung hibrida IPB-4 dan H-6, dan (3) mempelajari perubahan beberapa sifat kimia tanah. Lima taraf kapur (kalsit) yang setara dengan 0, 0.25, 0.5, 0.75, dan 1.0 kali Al-dd digunakan untuk memperoleh kejenuhan Al berdasarkan KTK efektif. Peningkatan dosis kapur cenderung meningkatkan Ca-dd, pH H2O, pH KCl, menurunkan Al-dd', sedangkan Mg, K dan Na dapat dipertukarkan relatif tetap. Aluminium berpengaruh nyata terhadap tinggi tanaman umur 2 sampai 6 minggu setelah tanam, bobot kering atas dan akar tanaman, kadar dan serapan Al akar, batang dan daun, serta Ca dan Mg daun. Pengaruh langsung Al umumnya pada sistem perakaran, sehingga fungsi akar yang terpenga- ruh dalam penyerapan air dan hara menurun. Kejenuhan (atau kadar) Al umumnya berkorelasi negatif dengan semua parameter, kecuali kadar Al akar dan kadar Al daun. Per- bedaan kemampuan untuk tumbuh dan menghasilkan cukup bahan kering dapat menjelaskan fenomena perbedaan toleransi dan serapan hara. Kadar Al akar berkaitan erat dengan kepekaan varietas terhadap Al. Pola-pola parameter menunjukkan bahwa hibrida H-6 lebih peka terhadap Al daripada hibrida IPB-4…
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Judul: Thermal Characteristics and Dynamics of Tropical Cyclone over Western North Pacific Ocean: A Case Study of Typhoon Songda (Chedeng) 2011
Abstrak: The frequent occasion of Tropical Cyclone (TC) over Western North Pacific (WNP) Ocean lies from 10˚N to 26˚N and 121˚E to 170˚E. Sources of TC development come from warm ocean temperature where latent heat is released during condensation processes and subsequently concentrated in the boundary layer. Relative humidity at 850-700 hPa is responsible to produce the most intense storm. Meanwhile, weak vertical wind shear between 850-200 hPa is one of the dynamical factors that lead to the development of TC. Pressure level of 850-200 hPa is chosen to minimize the thermodynamic effect in the lower troposphere. Typhoon Songda (Chedeng in the Philippines) or TSC lasted from May 18th to 30th, 2011 and strengthened into powerful Super Typhoon stage between May 24th and 27th. Long curving track and the exhibition of all sequences of TC life cycle, TSC is then considered as an ideal case of TC. The objective of the study with case of TSC is to investigate the role of thermal characteristics and dynamics on TC intensity. The research is carried out by using Advanced Research of Weather Research and Forecasting model (WRF ARW model) version 3.3. Two domains are employed in the model. The first domain situate from 02˚N to 40˚N and 118˚E to 149˚E and cover spatial resolution () of 33.1 km. The second domain situate from 09˚N to 27˚N and 119˚E to 132˚E with of 11 km. Timestep of the model () is 120 seconds. The model is supported by the following physical parameterization, i.e., Yonsei University Scheme (YSU) in the boundary layer, Kain-Fritsch scheme (KF) in the cumulus, and WRF Single-Moment 3-class scheme in the microphysics. Initial meteorological condition prior to the formation of the cyclone is generated using WRF ARW standard-release model. Sensitivity of the model output is obtained from a selected single-parameter change scenarios, namely, 10 % to 20 % decrease and increase of wind shear initial data at 850-200 hPa, and by 10 % to 20 % decrease of relative humidity initial data at 850-700 hPa. The result showed that the negative correlations between wind shear and intensity are found in wind shear scenarios. Wind shears of 10 ms-1 which lead to strengthening of the wind intensity in the early period of Typhoon development are found in wind shear scenarios. The effect of wind shear changes on wind intensity is statistically significant in the 20 % wind shear scenarios. During mature stage, weak wind intensity occurred when wind shear increase as given in the WRF standard-release and the 20 % decreasing scenario. Different situation is found in the 20 % increasing scenario where wind shear tend to weak and lead to strong wind intensity at this stage. Meanwhile, the reduction of moisture supply at 850-700 hPa resulting from 20 % decreasing relative humidity play a major role in the weakening of wind intensity and reduces mechanical energy of the cycle process as much as 300 J kg-1.
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