Physiological and Biochemical Effects of an Aqueous Extract of Lemna minor L. as a Potential Biostimulant for Maize

Biostimulants are receiving increasing attention for their beneficial effects on crops, driving interest in identifying new plant extracts that could exert such stimulatory effects. This work aimed to evaluate the potential of an aqueous extract obtained from duckweed (Lemna minor L.), a freshwater species, to act as a biostimulant in maize. For this purpose, duckweed plants were collected from a natural basin and then transferred, stabilized, and grown under controlled conditions. The duckweed extract was first characterized through untargeted profiling, which revealed an abundance of bioactive phytochemicals. A relatively high amount of low-molecular-weight secondary metabolites such as phenolics (6714.99 mg kg−1) and glucosinolates (4563.74 mg kg−1) were present in the plant extract. Maize seeds were primed with different concentrations of this extract (0.01%, 0.05%, 0.50%, and 1.00%, dry weight/water volume), and some physiological and biochemical traits of the crop were recorded. The duckweed extract improved maize germination, biomass, leaf area, pigment content, and vigor index. The most effective treatment was the 0.50% concentration, which improved the majority of the measured growth traits. The extract at concentrations of 0.05%, 0.50%, and 1.00% stimulated the assimilation of nitrogen (N), phosphorous (P), potassium (K), calcium (Ca), magnesium (Mg), sodium (Na), iron (Fe), and copper (Cu). In summary, this study revealed that duckweed is a promising species that can be cultured and grown under controlled conditions for obtaining extracts with biostimulant properties.