Microalgae enhanced plant growth and yield, and improved leaf color in soilless lettuce.

Microalgae can stimulate plant growth through bioactive compounds such as cytokinins, gibberellins, and abscisic acid. Here, we present novel insights into applying live microalgae cultures-Chlorella sp. and Scenedesmus obliquus-at different concentrations in lettuce cultivation, cv. 'Emocion'. Plants were grown in perlite under greenhouse conditions. Microalgae suspensions were prepared using fresh weight concentrations of 0.775, 0.0775, and 0.00775 g L-1, corresponding to cell densities of 2 × 107, 2 × 106, and 105 cells mL-1, respectively, and applied to the substrate as 140 mL per plant. The control received no microalgae application. Chlorella sp. significantly improved head weight and total yield, with the 0.775 g L-1 concentration being the most effective. Total yield increase was 18.3% compared to the control. For S. obliquus, the optimal effect was observed at 0.0775 g L-1, yielding a 2.7% higher yield than the control. Heatmap analysis revealed two primary treatment clusters, separating Chlorella sp. from S. obliquus and the control, with Chlorella sp. closely associated with yield-enhancing parameters. We concluded that Chlorella sp. application can effectively increase yield with 0.775 g L-1 identified as the most beneficial dose. Future research should investigate the mechanisms of microalgae-plant interactions and evaluate their applicability across various crops and cultivation systems.