Abstract
Lettuce (Lactuca sativa L.) is one of the most popular leafy vegetables, appreciated globally as a low-calorie food with bioactive compounds. The application of a low dose of abiotic stress is considered a sustainable pre-harvest strategy to modify the nutraceutical value of horticultural products. In this work, we explored the response of two differently colored (red or green) baby leaf lettuce varieties to four NaCl concentrations in the nutrient solution (from 1 to 30 mM), using a full factorial design. We focused on leaf morphological parameters and possible phytochemical enhancement of the main polyphenols and anthocyanins, analyzed by LC-MS. The response to low-to-moderate salt stress exposure was affected mainly by salt concentration for leaf traits or by the cultivar for leaf color, with very limited factors’ interactions. Multivariate analysis indicated a predominant role of the genotypic factor in shaping differences in the two weeks growing cycle for baby leaf lettuce. Phytochemically, different dose–response models to sub-optimal saline conditions may be applied to the various compounds. A significant hormetic stimulation was present only for cyanidin-malonyl glucoside, the main anthocyanin present in the red cultivar.
Highlights
Lettuce (Lactuca sativa L.) is an annual species of the Asteraceae family that has become one of the most popular fresh vegetables worldwide [1]
The evaluation of leaf traits at harvest indicated that the fresh weight of the harvested leaves per plant (LFW), water content (WTC), leaf area (LA) and number (LN), specific leaf area (SLA), and leaf succulence (LSH) were significantly affected by the genotype (Table 1)
Our study indicated that a short exposure to low-to-moderate salt stress caused divergent responses among phytochemicals in fresh cut lettuce growing at high density
Summary
Lettuce (Lactuca sativa L.) is an annual species of the Asteraceae family that has become one of the most popular fresh vegetables worldwide [1]. The growing appreciation of lettuce is due to the high level of antioxidants in relation to the low caloric value as well as its vitamin and mineral content [3,4]. Polyphenols share the ability of an antioxidant activity in vitro, with possible wide-ranging protective cellular roles [7]. This large and widespread class of phytochemical influences relevant commercial features of lettuce, such as the color and the damage-induced leaf browning [8,9]
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