Stimulatory Effect of an Extract of Lemna minor L. in Protecting Maize from Salinity: A Multifaceted Biostimulant for Modulating Physiology, Redox Balance, and Nutrient Uptake

Water and soil salinization significantly reduce crop yields. Among the strategies developed to counteract salt stress, biostimulants can maintain crop productivity, reversing its impact. In this context, there is interest in finding new substances that could act as biostimulants. Recently, the biostimulatory potential of Lemna minor L. (duckweed) extracts has been shown. This work aimed to highlight whether an extract from duckweed (Lemna extract—LE) could protect maize grown in salinity, exploring the mechanisms induced to improve crop resistance. Plants were grown by applying two concentrations of NaCl (150 and 300 mM), and some physiological, morphological, and biochemical traits were studied in control and salt-stressed samples, treated or not with LE. Salinity decreased shoots, roots, pigment, and soluble protein. LE prompted ameliorative changes at the root level and increased photosynthetic pigment and soluble protein. Furthermore, concerning the oxidative impairment provoked by salt stress, LE enhanced the cellular redox state, contrasting H2O2 and MDA accumulation and positively affecting the activity of superoxide dismutase (SOD—EC 1.15.1.1) and catalase (CAT—EC 1.11.1.6). The assessment of some mineral nutrients showed that LE stimulated their acquisition, especially for the highest salt dosage, explaining some benefits found for the parameters investigated.