1Laboratory of Horticultural Sciences, National Agronomic Institute of Tunisia (INAT), University of Carthage, 43 Av. Charles Nicolle-1082, Tunis, Tunisia
2Higher School of Agriculture of Kef (ESA Kef), University of Jendouba-7119, Le Kef, Tunisia
3Laboratory of Agricultural Sciences and Techniques, National Institute of Agricultural Research of Tunisia (INRAT), University of Carthage, Tunisia
4National Institute of Field Crops (INGC), Boussalem, Jendouba, Tunisia
5Research Laboratory Ecosystems & Aquatic Resources, National Agronomic Institute of Tunisia (INAT), University of Carthage, 43 Av. Charles Nicolle-1082, Tunis, Tunisia
Received:01 May 2025 / Accepted:28 July 2025 / Published Online: 09 August 2025
Abstract
Seaweed extracts are substances rich in numerous plant growth stimulating molecules such as macro and micronutrients as well as hormones and have been used in agriculture for decades for their renown activity in promoting plant development. This research was conducted to examine the efficiency of two aqueous seaweed extracts as biostimulants in enhancing the growth and mineral composition of lettuce (Lactuca sativa var. longifolia) grown in aquaponics. Therefore, lettuce plants were grown under a greenhouse in a Nutrient Film Technique aquaponic system. The green algae extracts were prepared from Chaetomorpha linum and Ulva linza and their application was done by foliar spraying. Results showed that C. linum extract positively affected lettuce growth and biomass production. Indeed, this treatment enhanced the majority of the parameters studied: a significant increase in the number of leaves (20.56 leaves developed per plant, P < 0.05), the root length (22.30 cm, P < 0.05) and the shoot dry weight (13.68 g, P < 0.05) was observed. The chlorophyll and carotenoids contents of aquaponically grown lettuce were enhanced by the application of the aforementioned treatment, nevertheless these differences were not statistically significant. Overall results related to the mineral composition highlighted the effectiveness of U. linza extract. This latter treatment has significantly improved the Ca (by 8.75%, P < 0.05), Fe (by 2.71%, P < 0.05), Cu (by 26.88%, P < 0.05), Mn (by 7.92%, P < 0.05) and Zn (by 45.35%, P < 0.05) contents in lettuce leaves. These findings prove the potential of the studied algae extracts as biostimulants, thus encouraging their use in the enhancement of aquaponically grown lettuce productivity.
Keywords: NFT, Chaetomorpha linum, Ulva linza, Nile Tilapia, Biostimulant
