Microalgal biomass application promotes growth and alleviates salt stress in melon plants stimulating antioxidant metabolism

High soil and water salinity are limiting factors for the growth and production of melon (Cucumis melo L). Therefore, the search for sustainable alternatives to mitigate the deleterious effects of salt stress is highly relevant. The aim of this work was to evaluate the effects of the concentration and form of application of the microalga Asterarcys quadricellularis on biometric and biochemical variables of two melon cultivars grown in conditions with and without saline stress. The experimental design was completely randomized with four replications in a triple factorial scheme: two cultivars (Goldex and Dal & iacute;), two growing conditions (with and without NaCl) and six A. quadricellularis application methods (foliar spraying, drip irrigation and the simultaneous application of foliar spraying and drip irrigation at concentrations of 0.5 mL L-1 and 1.0 mL L-1) in addition to the absence of microalgae application in the two growing conditions and in the two cultivars, totaling 28 treatments. Plants under saline conditions treated with the microalga showed a significant increase in chlorophyll, carotenoids, total free amino acids, proteins, proline, total sugars, phenolic compounds, and increased antioxidant enzyme activity, reducing lipid peroxidation. There was also a significant effect on biometric variables, providing an increase in fresh mass, stem diameter, fresh and dry stem mass, root length and number of flowers. Thus, A. quadricellularis stimulated metabolic changes mitigating the effects of salinity in both cultivars. Therefore, the application of this microalga can be a sustainable alternative for mitigating the effects of salt stress in melon plants.