The modulation of plant secondary metabolism by the manipulation of nutrient solution (NS) electrical conductivity and biostimulant application has the potential to increase crop growth and the content of bioactive compounds, thus ameliorating the qualitative attributes of vegetables. A Graminaceae-derived protein hydrolysate (pH) and its molecular fractions PH1 (>10 kDa), PH2 (1 < x <10 kDa) and PH3 (<1 kDa) were applied on lettuce grown in a soilless system and irrigated with two levels of NaCl in the NS (0 and 30 mM). The different pH fractions provided distinct responses, with PH2 in saline conditions increasing lettuce fresh weight by 10.48%, and decreased Na, Cl, malate and citrate concentrations in the leaves by 37.24%, 15.45%,31.4% and 33.73% compared to control. Similar results were achieved by the fraction PH3. However, pH and its fractions PH2 and PH3 increased total flavonoids in salinity conditions, while pH and its fraction PH3 increased total phenolic acids in both saline and non-saline conditions. At the same time, all the 3 fractions of pH increased lutein in both conditions. Therefore, pH fractions should be casted, under tailored conditions, to achieve the desired growth and modulation of qualitative attributes. Nonetheless, omic approaches should be further recommended to support and clarify the mechanisms of these fractions.

通过控制营养液 (NS) 电导率和生物刺激素的应用来调节植物次生代谢，有可能促进作物生长和生物活性化合物的含量，从而改善蔬菜的品质属性。禾本科衍生的蛋白水解物(pH) 及其分子级分 PH1 (>10 kDa)、PH2 (1 < x<10 kDa) 和 PH3 (<1 kDa) 应用于在无土系统中生长的生菜，并在 NS（0 和 30 mM）中用两种水平的 NaCl 进行灌溉。不同的 pH 级分提供了不同的响应，与对照相比，盐碱条件下的 PH2 使生菜鲜重增加了 10.48%，并且叶片中的 Na、Cl、苹果酸盐和柠檬酸盐浓度降低了 37.24%、15.45%、31.4% 和 33.73%。分数 PH3 获得了类似的结果。然而，pH 及其组分 PH2 和 PH3 在盐度条件下增加了总黄酮类化合物，而 pH 及其组分 PH3 在咸水和非咸水条件下增加了总酚酸。同时，在两种条件下，所有 3 个 pH 级分都增加了叶黄素。因此，应在定制条件下铸造 pH 级分，以实现所需的质量属性的增长和调制。尽管如此，应该进一步推荐组学方法来支持和阐明这些分数的机制。