Current plant growth trends coupled with advanced analysis and in-field monitoring are oriented towards new agricultural inputs that protect and stimulate plant development. New nano-formulations sprays are being developed in order to help plants fight biotic and abiotic stress (i.e., osmoprotectants, biostimulants, biopesticides, or elicitors) [1]. The main categories of plant biostimulants include protein hydrolysates, polyamines, aminoacids, other N-containing compounds, seaweed extracts (alginate), botanicals, chitosan, other biopolymers, inorganic compounds (Si, Se), beneficial fungi, humic acids, fulvic acids, and beneficial bacteria [1,2].
A solution of 1% chitosan (CS) was prepared by dissolving it in 1% acetic acid. Further, it was mixed with 0.5% gallic acid that was dissolved in ethanol. The mixture was rigorously shaken using a vortex for 30 min, which allowed the gallic acid to act as an ionotropic crosslinker for chitosan. The nanodispersion was added in a 0.2% bacterial nanocellulose suspension, previously obtained by purification and microfluidization of Kombucha pellicles [3], the cellulosic nanofibrils having the role of a stabilizing net. Alginate was added as a 1% water solution due to its muco-adhesive properties and final stabilization role as a hydrogel containing crosslinked chitosan-gallic acidnanoparticles.
The viscosity of the system with 1% CS was lower, which allows us to recommend it for further spray-drying formulations. The system with 3% CS was homogeneous and more viscous, suggesting a possible application as soil amendment for soils depleted in nutrients. The prepared nanoformulations have potential biostimulant activity due to polyphenolic gallic acid, water retention-releasing characteristics of highly hydrophilic NDBNC, and plant nutrition properties through chitosan and alginate decomposition.
The NDBNC-alginate hydrogel contains gallic acid-chitosan dispersed nanoparticles that can be used in their concentrated form as biostimulant hydrogel that can beapplied on soil around plants roots, or in a 100x diluted form for foliar application. These biostimulant nanoformulations can be used for plant growth and protection during drought periods.
Acknowledgments
This work was supported by the Romanian Ministry for Research and Innovation and National Authority for Scientific Research (ANCS) and Executive Unit for Financing Higher Education, Research, Development and Innovation (UEFISCDI) through the project NEXT-STIM PN.19.23.01.03 contract no. 23N/2019.
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