A novel biostimulant from chitosan nanoparticles and microalgae-based protein hydrolysate: Improving crop performance in tomato

Biostimulant compounds act on plant's growth and metabolism, increasing tolerance to abiotic and biotic stresses, besides allowing higher crop yields. Some of these compounds are unstable under certain environmental conditions, degrading during field applications. Nanoparticles have been applied in several areas including agriculture, allowing to preserve active compounds, increasing their solubility and stability, as well as the efficiency in delivering bioactive molecules to plants. This study firstly developed two lecithin/chitosan-based nanoparticle formulations (NP) as carriers of a Arthrospira platensis protein hydrolyzate (PH -68.9 mg mL- free amino acids) and further evaluated their effects on tomato plants metabolism and growth. The NP formulations containing the hydrolyzate did not differ as to their polydispersion index, zeta potential, and mean particle size. To test the effects on plant growth, tomato plants were transplanted into soil and weekly sprayed with PH (2 mg mL-1), its nanoderivative forms (NP) containing free amino acids (0.3, 0.8, 1.2, 1.6, and 2.0 mg mL-1), and NP control (without amino acids). NP and PH were effective in stimulating tomato growth, increasing by up to 49.5 % plant height in the vegetative phase. In the fruitage stage, NP treatments (0.3 and 0.8 mg mL-1) exhibited optimal outcomes, enhancing chlorophyll, carotenoid, flavonoid, and epigallocatechin amounts in leaves, alongside increased lycopene content in fruits. This confirms the growth-stimulating impact of the developed NPs on tomato plants both in vegetative and fruiting phases. These findings resonate with nanoliposome-encapsulated active compounds' exceptional efficiency, highlighting their potential for sustainable agricultural practices.