Different effects of cultivar and nutrition on the response of lettuce (Lactuca sativa L.) grown in the Nutrient Film Technique (NFT)

The aim of this study was to determine the effect of cultivar and varied nutrient solution composition on the quality and growth of lettuce grown in a recirculating NFT system. Three cultivars were tested: ‘Rouxai’ (oakleaf type), ‘Corentine RZ’ (Lollo Rossa type), and ‘Lozano’ (Lollo Bionda type), under four nutrient solutions varying in nitrogen (N) content (ranging from 62 to 150 mg dm-3) and the ratios of other macroelements. Chemical composition of the nutrient solution significantly affected plant yielding. Reducing N nutrition significantly decreased nitrate levels in plants, while also significantly reducing crop yields. When the N content was constant, an increase in the proportions of K, Ca, and Mg significantly enhanced yields, demonstrating that nutrient ratios are a key factor. The photosynthetic apparatus of plants was not affected by reduced nitrogen in nutrient solution, but effectiveness of photosynthesis express as a dry matter production was reduced. The response of plants varied depending on the cv: (1) ‘Lozano’ took up the most nutrients and achieved the highest fresh weight yield; the measured chlorophyll and fluorescence indices were not the highest. This cultivar accumulated high levels of nitrates (2) ‘Rouxai’ had the lowest fresh and dry weight, and stands out with the highest chlorophyll (Relative Chlorophyll Content and NDVI) and fluorescence indices (3) ‘Corentine’ shows generally balanced results in nutrient uptake, growth, and physiological parameters. Chlorophyll and fluorescence indicators are valuable diagnostic tools that reveal genotypic differences in response to nitrogen nutrition. The significant variability in plant response across cultivars confirms the difficulty in selecting cultivars suitable for mixed-pot cultivation intended for the consumer market.