Hydrogen sulfide (H₂S) has emerged as a gasotransmitter capable of exhibiting many beneficial properties in plants including the survival of plants under environment stressors, as well as increase their harvest yields. Although H₂S is an exciting new frontier in agriculture, what is needed in this field is a method to add chemicals that slowly release H₂S over well-defined time periods, will release biocompatible and safe chemicals in addition to H₂S, and will not diffuse away from roots of plants. Here, we report the addition of a dithiophosphate that will release H₂S slowly by hydrolysis and its encapsulation into microparticles of poly(lactic acid) [PLA]. The microparticles were prepared by a modified solvent evaporation technique. Tert-butanoldithiophosphate phenethylamine salt was loaded into PLA microparticles. The external morphology and the composition of the tert-butanoldithiophosphate phenethylamine salt loaded particles was examined by scanning electron microscope (SEM), powder X-ray diffraction (PXRD), and energy dispersive X-ray analysis (EDX). It was shown that surface of the microparticles was rough and contained tert-butanoldithiophosphate phenethylamine salt. The release profiles of tert-butanoldithiophosphate phenethylamine salt from the microparticles showed that 61% and 74 % of tert-butanoldithiophosphate phenethylamine salt was released at pH 7.2 and pH 6.0 respectively after 30 days. The H₂S release from the microparticles were determined using modified methylene blue method, and it was shown that nearly 20 μM and 12 μM of H₂S was released from 20% and 10% loaded microparticles respectively over 4 weeks. To demonstrate the potential applications of micro particles in agriculture, we also describe their effects on the growth of radish 4.5 weeks after exposure to milligram loadings of micro particles.

Nimesh Pasan Ranasinghe Ranasinghe Arachchige

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