No abstract

Iron toxicity stress causes physiological and metabolic changes in rice and other plants. To date, there is little information about the metabolite profile of rice under Fe toxicity conditions. In fact, metabolite has a contribution to the physiological condition of plants. Plant metabolomics is a study of low-molecular weight metabolites in plants under certain conditions. The objective of the research was to investigate physiological and metabolic changes in rice under Fe toxicity stress. Two-week-old seedlings of four rice varieties with various Fe toxicity tolerance levels were stressed hydroponically with 400 ppm FeSO 4. 7H 2 O for 10 d. Numerous physiological characters were observed and untargeted metabolomic analysis was carried out using gas chromatography-mass spectrophotometry (GC-MS). The results showed Fe toxicity induced physiological and metabolite variation in rice. By comparing the metabolites synthesized in Fe toxicity-stressed plants with control plants, it showed that elaidic acid, linoleic acid, and linolenic acid could be as metabolite marker candidates for rice response to Fe toxicity stress. When plants exposed to Fe toxicity stress, elaidic acid increased, whereas linoleic-and linolenic acid decreased. The alteration of fatty acid composition in the root and shoot suggests the alteration of metabolites is one of the tolerance strategies of rice to Fe toxicity stress. This finding offers an insight about the tolerance strategies of rice under Fe toxicity stress related to the maintenance process of the cell membranes during this stress. The genes underlying biosynthesis of the fatty acid could be a target of future research on responsible genes for Fe toxicity tolerance in rice.

<p align="center"><strong><em>ABSTRACT</em></strong></p>The effects of nitrogen fertilizer on agronomic and morphological characters depend on several factors such as genotypes and nitrogen rate. The study was aimed to evaluate nitrogen effects on rice panicle. A field experiment was conducted at Babakan Research Station during November 2015- February 2016 using a split-split plot design with three replicates. Nitrogen doses was a main plot, genotypes was a subplot, and time of application was a sub-subplot. A greenhouse experiment was carried out at PAIR, Jakarta during February-July 2017 using a completely randomized design with three replicates. The results from the field experiment indicated that the highest panicle number (13.25), number of filled grains (177.94) and spikelet number (213.76) were obtained at doses of 450 kg urea ha-1. Analysis of variance showed that the genotypic effects were significant for all traits observed, while the interaction effect between genotypes and time of nitrogen application was significant on the length of first grain from first node. However, the three-factors interactions were not significant for all traits. The greenhouse experiment revealed that both genotypes and N rates significantly affected all traits except for panicle number and the length of first grain from first node, respectively, while their interaction only significant for number of primary branch. Nitrogen increased all traits observed except the length of first grain from first node. Simultaneously, both experiments showed significant effects of genotypes for all traits observed. Doses of urea fertilizers above 400 kg ha-1 could improve the performance of panicle traits in order to increase yield potential.<br /><br />Keywords: length of first grain from first node, number of primary branches, panicle length, panicle number

ABSTRAKKepel (Stelechocarpus burahol) merupakan tanaman yang mempunyai khasiat obat dan hingga saat ini belum banyak informasi mengenai kadar bioaktifnya. Bioaktif yang terdapat pada daun kepel salah satunya flavonoid yang dapat digunakan sebagai antioksidan. Penelitian ini bertujuan untuk mengetahui kandungan bioaktif daun kepel pada umur daun yang berbeda. Penelitian ini dilaksanakan sejak Juni sampai November 2013 di Arboretum Lanskap IPB (Bogor, Indonesia). Bagian tanaman yang digunakan sebagai sampel yaitu daun muda, sedang dan dewasa. Rata-rata kadar bioaktif daun tanaman kepel pada masing-masing umur daun dibandingkan menggunakan uji t-student's. Hasil penelitian menunjukkan aktivitas enzim phenylalanine ammonia lyase (PAL) dan kadar antosianin pada daun muda relatif lebih tinggi dari daun tua dan daun sedang. Daun kepel dewasa memiliki kadar flavonoid dan total klorofil yang paling tinggi dari pada daun sedang dan daun muda. Kadar flavonoid daun kepel menurun, sedangkan kadar antosianin, aktivitas PAL dan total klorofil meningkat seiring dengan meningkatnya curah hujan. Daun kepel yang sudah dewasa dapat digunakan sebagai bahan baku obat.

Saturated soil culture (SSC) technology appropriate to prevent pyrite oxidation on tidal swamps and has been proved to increase the productivity of soybean on non-tidal swamp. The objective of the research was to determine the growth response of soybean varieties under saturated soil culture on tidal swamps. The research was conducted at Banyu Urip, Tanjung Lago, Banyuasin District, and South Sumatera Province, Indonesia from April to August 2009. The experiment was arranged in a split plot design with three replications. The main-plot of the experiment was water depth in the furrow consisted of 10, 20, 30, and 40 cm under soil surface (USS). The subplot of the experiments was soybean varieties consisted of Tanggamus, Slamet, Wilis, and Anjasmoro. No-watering was arranged out of the design as a comparison. The result showed that nutrient absorption of N, K and Mn by Tanggamus was higher than those of other varieties, except K, however K absorption of Tanggamus was not significantly different from Anjasmoro. P and Fe absorption of Tangamus tended to be higher than the other varieties, although statistically they were not affected by variety. However, technically and economically, 20 cm USS was the most appropriate water depth for soybean production at tidal swamps.