Cecropia peltata is popularly known as ''guarumbo'' in Mexico and is used in traditional medicine for treatment of diabetes mellitus. C. peltata plants were cultivated in a hydroponic system under controlled conditions. Gradients of light (20, 30 and 100 lmol m -2 s -1 ) and nitrate concentrations (13, 2 and 0.2 mM) were applied to estimate their effect on biomass allocation and accumulation of bioactive (chlorogenic acid and isoorientin) phenolic compounds over a 28-day period. According to carbon nutrient balance (CNB) hypothesis predictions, biomass accumulation in foliage was stimulated by the highest irradiance (100 lmol m -2 s -1 ); similarly, at highest irradiance in combination with lowest nitrate concentration (0.2 mM), root growth was stimulated (root-toshoot ratio increased twofold with respect to the control). In these conditions, total phenolics (TP) and chlorogenic acid (CGA) contents were higher in aerial parts than in roots, with a 3.8-fold increase in TP and a 7.7-fold increase in CGA in foliage with respect to the control plants.Isoorientin was accumulated at very low levels. Antioxidant activity and total phenolic content showed a strong positive correlation. Phenylalanine ammonia-lyase activity (PAL) in aerial parts exhibited significant changes ([twofold) by highest irradiance. C. peltata plants allocate biomass and/or phenolic compounds to compensate the oxidative damage (increase in MDA levels) due to changes in light and nitrate restriction. The results are the basis for the establishment of a system of C. peltata culture in view of the potential use of C. peltata in therapeutic preparations for the treatment of diabetes mellitus.

Nitrogen (N) fertilizers have a decisive influence on the yield and quality of tobacco. Yield, percentage of plant N, wrapper leaf quality, and nicotine content are all important quality characteristics in tobacco growing. This work is an attempt to provide a tool for optimizing mineral N nutrition for Cuban cigar tobacco, using a strategy that links N supply with leaf N concentration and wrapper yield. Similar approaches developed worldwide have mainly involved Virginia and Burley tobacco types but not Cuban cigar tobacco. The objective of the current work is to identify the effects of fertilizer N levels and timing of application on each of the mentioned quality factors for shade grown Cuban cigar tobacco. Another purpose is to explore the usefulness of a quick method of assessing the N status of plants based on measuring leaf transmission at two different wavelengths (650 and 940 nm). The experiments were done in the main tobacco growing area of Cuba (Vueltabajo). In each experiment, nine separate treatments were used covering different levels and times of fertilizer N application. The same experiment was carried out in three different years (2005-2006, 2006-2007, 2007-2008) but as the results were similar only one set of data is described (2006-2007). The patterns of response to N fertilizer of all four quality measurements, including yield and wrapper leaf quality, were similar in the different replications of the experiments. The optimal fertilizer level was 140-190 kg N/ha (40% applied on days 8-10 after transplanting and 60% on days 18-20 after transplanting). The optimal N concentration of leaves taken at the central foliar level of the middle stalk position was 4.3-4.7% at harvest time. Leaf transmission measurements by means of the SPAD-502 Chlorophyll Meter in the early stages of growth were correlated with leaf chlorophyll and N concentration and provide an excellent guide for predicting Cuban cigar tobacco wrapper leaf yield.

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