Growth and quality of leafy vegetables in hydroponics: effect of environmental and nutritional factors.

The aim of the PhD thesis was to evaluate the influence of environmental conditions and mineral nutrition on growth, mineral composition and quali-quantitative traits of Lactuca sativa L. var. acephala and two Brassica species (Brassicia juncea L. and Brassica rapa L. subsp. nipposinica var. chiloneifera). In lettuce experiments, the effects of five nutrient solution concentrations (with the same macro-nutrient proportion) and six nutrient solutions having different macro-nutrient proportions (at the same total concentration) were evaluated in two consecutive growing seasons (spring and summer season) while the effects of three NO3:NH4 ratios in the nutrient solution and three radiation levels were tested in Brassica experiments. The results showed that during the summer season the growth and yield of lettuce were increased due to the better climate conditions (mainly radiation and temperature). However, the overall quality of lettuce in the summer season was decreased (lower content of carbohydrates and higher nitrate content). The use of nutrient solution concentration of 37 and 44 mequiv L-1 gave the maximum marketable fresh yield for the spring and summer season, respectively. In the second experiment, the effects of macronutrient proportions on marketable fresh yield were not evident; the macronutrien

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