Effect of foliar application of amino acids biostimulants on growth, macronutrient, total phenols contents and antioxidant activity of soilless grown lettuce cultivars

Biostimulants containing amino acids and minerals have been used commercially to promote plant growth, yield and nutritive value of food crops. Limited studies on biostimulants application are available on lettuce production in soilless systems. This research was conducted to determine the effects of foliar application of amino acids biostimulants (PerfectoseTM, liquid) on yield and leaf quality of two lettuce cultivars, romaine and iceberg, under soilless conditions. Plants of both lettuce cultivars were sprayed with three different concentrations of Perfectose at 0 (control, only water), 2 and 4 ml L-1. Perfectose was applied twice during the crop cycle. Foliar application of Perfectose resulted in increasing lettuce fresh yield by 25.7 and 39%, dry yield by 28.6 and 55.3% and leaf number per head by 18.8 and 22.8% over control for iceberg and romaine cultivars, respectively. In comparison to untreated plants, applica-tion of Perfectose at the rate 4 ml L-1 had increased leaf nutrient contents of N, P, K and Mg, phenols, flavonoids and antioxidant activity by 20.5, 25.1, 19.8, 58.5, 28.4, 30.6 and 35.7%, respectively over both cultivars. Romaine cultivar has produced higher fresh and dry yields, leaf number, leaf N, P, K, Mg, total phenols and flavonoids contents and antioxidant activity in comparison to iceberg cultivar especially at 4 ml L-1 rate. However, the iceberg cultivar was more responsive (in terms of percentage change) to Per-fectose application by generally enhancing leaf N, K, total phenols and flavonoids contents and antioxi-dant activity than in romaine cultivar. Therefore, application of amino acids stimulant Perfectose is considered efficient in enhancing the yield and nutritive value of lettuce and the efficiency is dependent on used cultivar under soilless conditions.(c) 2023 SAAB. Published by Elsevier B.V. All rights reserved.