• lycopene
• leafy lettuce
• Lactuca sativa L.
• image analysis
• floating system
• carotenoids
• colour
• calcium chloride
• Atroviolaceum (Atv) tomato
• salinity stress
• antioxidant capacity
• Anthocyanin fruit type (Aft) tomato
• Sun Black tomato.

Epidemiological and clinical investigations have linked diets rich in fruits and vegetables to a reduced risk for several diseases such as cardiovascular, neurological and chronic disorders as well as various types of cancer (Ames et al., 1993; Block, Patterson and Subar, 1992; Joseph et al., 1999; Steinmetz and Potter, 1991; Surh, 2003). These healthy properties of fruit and vegetables are related to the presence of phytochemicals compounds, which are also responsible for their colours. Pigmentation is due to three families of molecules: chlorophylls, carotenoids and anthocyanins. It is well known that the amount of each antioxidant in vegetables is strongly influenced by genotype differences in addition to agronomical, geographical, and environmental factors such as light, temperature, irrigation and mineral nutrition (Raffo et al., 2002, Wu et al., 2004; Serio et al., 2004; Raffo et al., 2006; Hernanz et al., 2008).
The goal of this research project was to study the content of antioxidants in two important horticultural crops: lettuce and tomatoes. In particular, the aim of the thesis was to evaluate how genetic factors and growing conditions may influence the quality of the product, with regard to phytochemical compounds content.
In the experiments on Lactuca sativa L., grown in a floating system, we noticed that decreasing nutrient concentration (down to 50%) did not result in substantial differences in yield although there was an increase in quality, and in particular a reduction of nitrates. Genotypic differences were also found between the cv Lollo rossa and Green Salad Bowl (GSB). GSB, grown under the same conditions, had a higher yield and lower nitrate content in the leaves than Lollo rossa but also had a lower content of antioxidant compounds.
A moderate salinity stress with calcium chloride did not affect the yield of Lactuca sativa L. var Lollo rossa, while it increased some nutraceutical characteristics such as phenol and antioxidant power content, particularly when the electric conductivity of the nutrient solution was between 3 and 6.4 dS m-1. Salinity also reduced nitrate contents in leaves. Ca in nutrient solution could therefore be used as a means to reduce some physiological unbalances due to salinity, such as the uptake of micro and macro-elements.
In the studies on tomato, we evaluated the content of antioxidants (carotenoids, flavonoids and anthocyanidins) in fruits hydroponically grown in greenhouses, during two different seasons and harvested at different stages of ripeness (green, turning and ripening red). We compared commercial cultivars particularly rich in antioxidant metabolites (lycopene) and genetic lines with high content of anthocyanins. Quantitative and qualitative parameters were influenced by genotype and period of cultivation. In almost all the cultivars quality characteristics such as sugar content and organic acid were found, to be higher in the summer production than in the winter one, while the carotenoid content was lower in the summer.
In Anthocyanin fruit type (Aft) and SunBlack (SB) fruits, we identified a number of anthocyanidins: delphinidin, petunidin, pelargonidin and malvidin. In particular, in the skins of SB mature fruits, the recorded values of petunidin were twice those found in Aft.
Finally, we have analyzed a non-anthocyanin-accumulating (Ailsa Craig) and three anthocyanin-accumulating tomato genotypes (Anthocyanin fruit type, Atroviolaceum and Sun Black) in order to evaluate differences in their total anthocyanins content, carotenoids levels and colours and to assess the effect of different salinity levels on those parameters. The salinity stress led to 2-3-fold increases in the lycopene content of some genotypes. Overall, the treatment accentuated the colour differences between purees and increased the accumulation of total anthocyanins in SB fruits (2-fold increase) while it reduced the accumulation in Aft fruits (10-fold decrease). The saline treatment favoured the accumulation of total anthocyanins in SB while it reduced their accumulation in Aft.