Utilization of Chlorella sp. as biostimulant in the germination of melon seeds (Cucumis melo L.)

Bioactive microalgae compounds have been shown to be excellent stimulants for seed germination. This study aimed at the production of biomass of Chlorella sp. through the modulation of the culture medium and its further use as bioestimulant in melon seed germination (Cucumis melo L.). Chlorella sp. cells were grown in medium containing distinctive levels of nitrogen (N), phosphorus (P), potassium (K) and carbon (C), and analyzes of yield, hygroscopic behavior and the amino acid profile of the biomass were carried out for all treatments. In addition, mechanical hydrolysis of the biomass through high-energy wet grinding was performed, obtaining suitable particle size. After biomass characterization, an aqueous solution of the hydrolyzate was used for biostimulation of melon seeds. The different growth medium composition affected biomass yield and amino acid profile. The most significant effects for seed biostimulation were obtained during growth in medium containing intermediary or low levels of NPK and C, with germination index (GI) of 92 and 95%, and germination speed index (GSI) of 8.00000 and 8,26087 seedlings.day-1, respectively. It is concluded that the modulation of the cultivation of Chlorella sp. is a viable strategy for the production of active compounds. The hydrolysates of Chlorella sp. demonstrated a biostimulant potential and can be a source of molecules for many applications in agriculture.