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A series of biochemical parameters, including the concentration of total ascorbic acid (ASA(tot)) and the activities of phenylalanine ammonia lyase (PAL), polyphenol oxidase (PPO), and peroxidases (PODs), was investigated during cold storage (72 h at 4 degrees C in the dark) in fresh-cut (minimally processed) leaves of two lettuce (Lactuca sativa L. var. acephala) cultivars differing in the susceptibility to tissue browning: Green Salade Bowl (GSB), susceptible, and Red Salade Bowl (RSB), resistant. The two cultivars showed differences also at the biochemical level. The content in ASA(tot) increased in RSB, as a consequence of increased DHA concentration; conversely, ASA(tot) diminished in GSB, in which ASA was not detectable after 72 h of storage, thus suggesting a disappearance of ascorbate (both ASA and DHA) into nonactive forms. The antioxidant capacity (as determined by using FRAP analysis) decreased significantly during storage in RSB, while a strong increase was observed in GSB. PAL activity increased soon after processing reaching a maximum by 3 h, then it declined to a relatively constant value in RSB, while in GSB it showed a tendency to decrease in the first few hours from harvest and processing. POD activity, at least for chlorogenic acid, increased significantly during storage only in GSB.

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The production innovations have been evolving more and more towards organic, sustainable or environmental friendly systems. Contemporarily, the yield and the quality of crops must be assured. The reduction of fertilisers may be obtained by improving the nutrients uptake or their utilisation by the plants. The aim of our work was to verify if the progressive reduction of nutrient solution concentration in the floating system can be compensated by applications of a biostimulant (Actiwave®, Valagro S.p.a.) without compromising the yield and the quality of vegetables. The experiments were performed on rocket (Eruca sativa Mill.) grown in floating system with standard nutrient solution (NS100%), which was compared with nutrient solutions diluted 4 (NS25%) or 10-fold (NS10%) with or without 0.3 ml L-1 Actiwave. At harvest, yield, leaf area, root dry weight, chlorophyll, carotenoids, and leaf nitrate content were determined. Results showed that Actiwave significantly increased the nutrient uptake and nutrient use efficiency in all treatments. In fact, no statistically significant differences were found in yield between NS100% and NS25% plus 0.3 ml mL-1 Actiwave. Moreover, Actiwave reduced the leaf nitrate content and increased chlorophyll and carotenoids in all treatments. Our results indicate that Actiwave lowered the leaf nitrate content through its ability in stimulating nutrient uptake and nitrogen metabolism. The combination of hydroponics and biostimulants appears as a promising environmental friendly strategy for the greenhouse production of highquality vegetables.