Can atmospheric plasma change the physical-chemical characteristic and the germination potential of Pityrocarpa moniliformis (Benth.) and Senna siamea (Lam.) seeds?

Abstract

Plasma consists of an atmosphere formed by one or more partially or totally ionized gases consisting of molecules, ions, radicals, atoms and electrons which interact with each other and form a reactive environment capable of modifying surfaces, configuring itself as an innovative technology for this purpose. The present work evaluated the effect of plasma generated by a dielectric barrier discharge (DBD) source on the physical, chemical and germinative characteristics of Pityrocarpa moniliformis (Benth.) and Senna siamea (Lam.) seeds. The seeds were submitted to plasma obtained by dielectric barrier in coplanar plates with a voltage of 10 KV and a frequency of 4KHZ for 10 minutes. The seeds of both species had their physical structures analyzed using scanning electron microscopy (SEM). The crack areas were calculated using the ImageJ® software program. Chemical analyzes were performed using a Fourier transformed infrared spectrometer (FTIR) with whole seeds to obtain wavelengths in the region between 400 to 4000 cm-1. A completely randomized design was used for the germination test, with four replications of 25 seeds for each species in a controlled environment at 25ºC. To do so, the seeds were distributed on Germitest paper soaked with distilled water for 18 days, with the germination percentage, germination speed index (GSI) and daily germination being evaluated. The data were subjected to analysis of variance and the treatment means were compared at a significance level of 5% probability using the Tukey test. All statistical analyzes were performed using the System software program for statistical analysis of agronomic trials (AgroEstat) version 1.0. The result of the plasma application in the seeds of both species was satisfactory, as it modified the physical and chemical structure, thereby providing an increase in the germination percentage of P. moniliformis, but did not promote changes capable of increasing germination in S. siamea seeds. With the obtained results, the DBD plasma constitutes an efficient technique to overcome seed dormancy by modifying the physical structure and chemical properties, providing an increase in the germination of P. moniliformis. However, it was not able to alter the impermeability of S. siamea seeds.