The aim of this research was to evaluate butterhead lettuce quality in a soilless culture system. Butterhead lettuce cultivar "Lores" was cultivated, and two experiments were performed. In the first, floating system (FS) and soil culture (SC) were compared in fall (autumn) prduction [2002-2003], while in the second, substrate culture (PC) (plastic gutter filled with perlite) with three different levels of calcium (0, 3, and 6 me L-1) in the nutrient solution were compared in spring production [2003]. Growing cycles varied according to the culture system. In general, plants harvested from the soilless culture had a lower dry weight and leaf area, however significant differences were observed in productivity. Nitrate content was significantly affected by the production system. Ascorbic acid content showed no differences resulting from treatments. Floating system results showed some variation between the two years of the experiment. Inorganic cation differences were observed between plant harvest from all systems, especially in K + and Mg 2+. Colour intensity changes between production systems were insignificant. No variation in incidence of tip-burn relating to different calcium levels was found in lettuce grown in perlite.

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RESUMENLos nitratos (NO 3 -) ingeridos por el hombre pueden convertirse a nitritos (NO 2 -) formando metahemoglobina y nitrosaminas carcinogénicas. La lechuga se encuentra entre las hortalizas con mayor capacidad de acumulación de nitratos. El objetivo del estudio fue evaluar la respuesta del cultivo de lechuga a dosis crecientes de nitrógeno aplicado como urea y al agregado de lombricompuesto, sobre la concentración de nitratos en dos tipos comerciales (hoja suelta y mantecosa). En un ensayo se incorporó abono orgánico 24 t ha -1 de lombricompuesto (L1) y se comparó un testigo sin abonar (L0). En simultaneo se realizó un ensayo que comparó un testigo sin fertilizar (N0) con 75 kg N ha -1 (N1) y 150 kg N ha -1 (N2) aplicado como urea. Estos ensayos se realizaron en dos épocas de producción: otoño-invierno y primavera. En los experimentos, el diseño experimental fue en bloques completos al azar con parcelas divididas y con 4 repeticiones. Durante el cultivo y a la cosecha se determinó la concentración de NO 3 -por colorimetría. Se observó un nivel decreciente de nitratos para ambos ensayos durante el período invernal. El genotipo influyó en la concentración de nitratos, según tratamientos y épocas. Para el tratamiento con lombricompuesto se evidenció una mayor proporción de nitratos para 'Brisa' (hoja suelta) en ambas épocas. En otoño-invierno, 'Brisa' reflejó respuesta a la fertilización con urea mostrando mayores niveles de nitratos a cosecha con respecto a 'Daguan'. En primavera no hubo respuesta a la fertilización y solo el tratamiento con 150 kg N ha -1 (N2) en 'Brisa' presentó mayores niveles de nitratos en hoja a cosecha.Palabras clave: fertilización química, urea, lombricompuesto, compuestos carcinogénicos, nitritos. ABSTRACT Nitrate (NO 3-) can transform into nitrite (NO 2 -) in the human body and nitrites can change normal hemoglobin to methemoglobin, contributing to the formation of carcinogenic nitrosamines. Lettuce is one of the vegetables with a high capacity to accumulate nitrates. The objective of this study was to evaluate the response of lettuce to increasing doses of nitrogen applied as urea and the addition of vermicompost on the nitrate leaf content of two commercial types of lettuce: cv. Daguan (butterhead) and cv. Brisa (loose-leaf). Two field trials were conducted simultaneously in two growing seasons: autumn-winter and spring. One trial consisted of compost 24 t ha -1 vermicompost-(L1) added and a control treatment (L0) with no amendment, while the other treatment consisted of 75 kg N ha -1 (N1)

Horticultural crops have a strong impact on human nutrition. Lettuce is the most important leafy vegetable in Argentina and it is cultivated mainly in green belts, in greenhouses or open field. The aim of this study was to evaluate growth and phytonutrients concentration of leaf lettuce under greenhouse and field production. Crop establishment was made from seedlings produced in a commercial greenhouse. Loose lettuce cv. Brisa was used for field and greenhouse growth. Experimental design with complete random block with 4 replicates per treatment was used. Fresh and dry weights of shoot, number of leaves, color, ascorbic acid, chlorophyll content were measured. Absolute and relative growth rate and commercial yield were calculated. Lettuce grown under greenhouse system showed, as expected, a higher value of fresh and dry weight, number of leaves, leaf area, yield and absolute and relative growth rate. Ascorbic acid value of the leaves decreased during lettuce growth in both production systems. Chlorophyll content was higher in the greenhouse cultivation but the antioxidant capacity was lower in lettuce leaves from greenhouse than the leaves grown on open field.

The aim of this study was to evaluate the effect of two light environments on two maturity stages of sweet pepper and the postharvest behavior of minimally processed product using passive modified atmosphere. The size and fruit morphology were measured at harvest. Overall visual quality, gas concentration inside the bags, weight loss, soluble solids, firmness, electrolyte leakage, carotenoids and ascorbic acid were determined during the storage period. Results showed that quality parameters were affected by radiation and processing. Shaded pepper fruits showed higher water content and lower size compared to fruits exposed to full radiation. Fruit nutritional value was maintained, but after six days was not marketable. Visual quality of intact fruit was not affected without differences between treatments. Shelf life processed red fruits as julienne was reduced, being the worst performing during storage. Post-harvest visual quality was in relation to gases composition (O 2 and CO 2 ) inside the trays.