Three chromatographic techniques were compared to determine the solubilized phenolic compounds, from sugarcane bagasse pith pretreatment. Reverse phase gradient system I, was chosen as a technique to be evaluated in aromatic compounds determination, because it presented good selectivity, reproducibility and percent recovery of phenolic compounds. However, gradient system 11, and ionic exchange, resulted in longer resolution time, even though they had good resolution and selectivity. The amount of aromatic compounds determined by reverse phase gradient elution, were in decreasing order: 4-hydroxycinnamic acid (p-coumaric acid), 4-hydroxy-3-methoxycinnamic acid (ferulic acid), 4-hydroxybenzaldehyde(p-hydroxybenzaldehyde),4-hydroxy-3-methoxybenzaldehyde (vanillin), and 4-hydroxy-3-methoxybenzoic acid (vanillic acid). Reverse phase gradient system I, can be useful to identify and quantify the phenolic compounds solubilized in other lignocellulosic materials.From the experimental design 23 , the most important effect on total phenolic compounds solubilization, were: alkali concentration, temperature and alkali-moisture content interaction. In addition, the maximum amount of these compounds were obtained at high levels of experimental conditions, that is; 10% NaOH (ODW), 50 OC of temperature, and 80% of moisture content. 369

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BackgroundTolerance to the enrichment of ionic nitrogen (N) with ammonium (NH 4 ) and nitrate (NO 3 ) needs to be distinguished in a submerged grass ecotype-species of freshwater wetlands. Concentrations of total Nitrogen (TN: 500 to 2000 µgL -1 ) and three N sources (NS: NH 4 , NO 3 , 1:1 NH 4 :NO 3 ratio) in an overlaying aqueous phase, using local tap water as control (174 µgL -1 TN), were evaluated in rooted autotrophic juvenile Vallisneria americana established in vitro in two-phase culture medium. The treatments ranged from 7 to 111 µM TN. Phenotypes changes, pH and ionic strength in the aqueous phase were registered at 15 days. In addition, biomass of lyophilized leaf and root as well as N contents (gas and high-performance liquid chromatography) were analysed to estimate accumulations of N-NH 4 , N-NO 3 and N-NO 2 .ResultsAll individuals showed phenotypic similarities. Accumulation of N-NH 4 was discarded, but the accumulations of N-NO 3 and N-NO 2 in both tissues were significantly different (p<0.001 and 0.0001), revealing so much that the maximum cumulative responses coincided with a deficit of N as both showed a linear decrease in their cumulative capacity linked to an increase in micromolar TN. ConclusionsThe results provide direct evidence of the tolerance to N enrichment with three different N sources in the focal ecotype at the seedling stage, based mainly on its cumulative capacity of N-NO 3 and N-NO 2 under eutrophic conditions. The findings imply that NO 2 is a relevant ion in the tolerance to N enrichment in overlaying water with NH 4 and NO 3 ions. Future studies of N cumulative effect with an in vitro approximation will be to support stress predictions by N enrichment. Keywords : Hydrocharitaceae. Eutrophization. Stress in vitro. Ammonium. Nitrate. Nitrogen endogenous