Marine microalgae extracts as plant biostimulant to boost baby leaf lettuce production

The application of biostimulants derived from microalgae may represent a promising strategy to enhance fruit and vegetable yields, particularly in the context of ongoing climate change. Yet, comprehensive studies assessing the efficacy of specific marine microalgae species on leafy vegetable crops are still limited. Addressing this gap, the present work aimed to evaluate the effects of two marine microalgae Nannochloropsis gaditana and Porphyridium sp. on the growth and quality of baby leaf lettuce (Lactuca sativa L.). Extracts from both species were first chemically characterized and then applied via foliar spray in aqueous solution. At the end of the cultivation cycle, both treatments significantly enhanced nitrogen assimilation and water uptake, leading to increased biomass production. Notably, plants treated with microalgae extracts exhibited higher fresh weight (+ 31%), increased leaf number and plant height. Additionally, both treatments improved nutrient use efficiency and contributed to more effective water management. Gene expression analysis further revealed that extracts from N. gaditana and Porphyridium sp. modulated the expression of genes involved in nitrogen uptake and assimilation, supporting the observed improvement in nitrogen agronomic efficiency in lettuce. Collectively, these findings support the potential of N. gaditana and Porphyridium sp. as eco-friendly biostimulants capable of enhancing the sustainability and efficiency of leafy vegetable production systems.