It is known that lettuce (Lactuca sativa L. var. crispa L.) phenological stage and environmental changes can cause changes in the plant cell morphology and an important variation in secondary plant metabolites. Antioxidant compounds are beneficial to health and salinity can increase them. The aim of this study was to determine the effect of salt concentration (NaCl 0.05 and 0.1 mol L -1 ) and harvest time (days 10, 20 and 30) on mass, color parameters, antioxidant compounds and proline concentration as well as the morphological tissue changes on two lettuce cultivars: Lollo Bionda 'Levistro' (green leaves) and Lollo Rosso 'Carmoli' (red leaves). NaCl treatments and time of harvest affected fresh matter (FM), DM and DM%, total phenol content, concentration of anthocyanin and antioxidant capacity of both cultivars. High NaCl concentrations decreased FM (from 16.8 to 8.7 g in 'Levistro' in 3 rd harvest) and the intracellular space of the leaf tissue but increased the concentration of proline (from 19.6 to 292.2 μg 100 g -1 FM in 'Levistro') and antioxidant compounds (from 412.9 to 487.3 mg Trolox eq. 100 g -1 FM in 'Levistro'). In addition, concentrations of antioxidant compounds (from 458.2 to 506.4 mg Trolox eq. 100 g -1 FM in 'Levistro') and cell density were significantly higher in late than early harvested plants. Thus, successive harvesting may lead to higher antioxidant capacities of lettuces leaves. A moderate decline in FM, a higher cell density and proline concentrations may indicate the better adaptability to salinity stress of red 'Carmoli' than the green 'Levistro' lettuces.

Changes in plant responses have been associated with different fractions of the visible spectrum and light intensity. Advances in light emitting diodes (LED) have enabled the study of the effect of narrow wavelengths on plant growth and antioxidant compound synthesis. LED technology also facilitates the incorporation of light sources in a controlled setting where light spectra and intensity can be regulated. The objective of this study was to compare the effect of two commercial light spectra (S1: standard white light with 32.8% blue, 42.5% green, 21.7% red and 2.4% far red;S2: AP67 spectrum, designed for horticultural growth, with 16.9% blue, 20.5% green, 49.7% red and 12.3% far red) at two light intensities [LI: low intensity (78 µmol·m-2s-1 of photons for S1 and 62 µmol·m-2s-1 for S2, and HI: high intensity (102 and 100 µmol·m-2s-1 for S1 and S2, respectively)] on growth and antioxidant compound contents in two leafy vegetables: endive (Cichorium endivia L.) and lettuce (Lactuca sativa L.). Fresh weight (FW), dry weight (DW), and DW% of plants were taken as growth indicators. Leaf number, SPAD index, leaf area (LA) and specific leaf area (SLA) were also evaluated. Antioxidant synthesis was measured as total phenol content (TPC), total flavonoid content (TFC) and antioxidant activity (AA). The results showed that S2 and HI increased the FW, DW, and LA in both species. On the other hand, antioxidant compound contents were significantly increased by HI but did not vary with the spectrum.

Aquaponics is the integration of aquaculture and hydroponic systems where, in general terms, the waste produced by aquatic organisms becomes nutrients through bacterial action for plant growth. Water consumption as well as the environmental impact in this type of system are lower compared to more traditional hydroponic and aquaculture counterparts, due to its dual productive nature and closed condition of the system allowing the reuse of water and fish waste. The present study evaluated the yield, nitrate concentration, microbiological and functional quality of lettuce (Lactuca sativa L.) grown in two production systems: aquaponics and hydroponics. At the same time, fresh mass gain and feed conversion ratio (FCR) of rainbow trout (Oncorhynchus mykiss) were assessed. Lettuces were grown in an aquaponic system using waste water from the fish system, as well as in a hydroponic system with nutrient solution (Hoagland II-modified) both for 21 days. At the end of this period, baby lettuce (8 and 12 cm of length) was harvested. The yield of lettuce grown in aquaponic system was 6.73% higher than that of grown in hydroponic system. Also aquaponically grown lettuce had lower nitrate concentration (1079 mg kg-1 FW) than hydroponically grown lettuce (1229 mg kg-1 FW). Lettuces grown in both systems showed no significant differences in the microbial and functional qualities. Rainbow trout in the aquaponic system increased 13.6 g over 27.1±0.8 g initial fresh weight, obtaining a FCR of 0.74 after the experiment. These results indicate that the aquaponic system used in the present study is a sustainable alternative for the production of high quality lettuce considering its high yield, lower concentration of nitrates and similar microbiological and functional qualities compared to hydroponic systems, while allowing simultaneous fish farming with a good feed conversion ratio (74 g of food was needed to produce 100 g of rainbow trout).

has increased in recent years, so it is imperative for the industry to fill expectations in terms of convenience, taste and product quality. Consumers are looking for freshness and soft textures, so baby leaf vegetables are the most promising choice for the development of minimal processing industries. The cultures of baby leaf vegetables have increased due to it fast processing operations and its attractiveness as a gourmet product. Despite these benefits, the short shelf life and fragility are important limitations. In addition, the limited availability of irrigation water and agricultural soils must be optimized. Hydroponics are shown as a valid alternative. This type of culture facilitates the interventions as abiotic stress in order to increase beneficial compounds and prolong postharvest life. The purpose of this study was to compare the separately responses of ?Lollo Bionda? lettuc