On the air atmospheric pressure plasma treatment effect on the physiology, germination and seedlings of basil seeds

Abstract

Basil (Ocimum basilicum) seeds were treated for different exposure times with a non-equilibrium plasma produced by a volume dielectric barrier discharge in humid air at atmospheric pressure. Plasma treatment did not change the seed structure and morphology, as visualized by high-resolution computed x-ray microtomography. A faster and higher germination rate was observed with plasma treatment of 1 and 3 min. Plantlets grown in sand, after both 2 and 3 weeks, showed a more developed root apparatus and better biometric parameters, compared to plants developing from non-treated seeds. After the plasma treatment, internal redistribution of macro and micronutrients was observed by using micro x-ray fluorescence spectroscopy. In particular P, K and Mg concentrated in the radicle, moving from the endosperm and cotyledons, while Zn, initially concentrated in specific tissues of the cotyledon, appeared more homogeneously distributed inside the whole seed after the plasma treatment. Significant variations in electrical impedance spectra were also observed after plasma treatment. This element redistribution in the seed was caused by the intense electrical field generated by the volume dielectric barrier discharge plasma, causing a movement of important micro and macronutrients from the storage regions of the seed towards the radicle tissues. This ion movement could explain the observed faster germination of the plasma-treated seeds. Indeed, such movement of ions is similar to what is generally observed in seed tissues during germination. The plasma treatment therefore somehow anticipates and implements the mobilization of key nutrients towards the radicle, resulting in faster and higher germination of the seeds as well as improved characteristics of the basil plantlet, especially at the root level.

Mechanisms of Plasma-Seed Treatments as a Potential Seed Processing Technology

“…Ambrico et al [50] instead used µ-XRF and showed the concentration and redistribution of macro-and micronutrients such as potassium after plasma treatment. As an example, on the one hand, the diffusion of potassium into the seed interior may improve the germination through enzyme activation, help with water retention, or detoxify ROS [134].…”

Plasma agriculture: Review from the perspective of the plant and its ecosystem

“…The direct treatment of seeds is predominantly performed with dielectric barrier discharges (DBDs) in ambient air. [ 51,65–92 ] The seeds are, thus, exposed to a variety of long‐ and short‐lived RONS (e.g., O, OH, O 3 , H 2 O 2 , N, NO, NO 2 − , NO 3 − ) and, in the case of volumetric DBDs (VDBD), to ions and the electric field. [ 93 ] Most studies report plasma dose‐dependent increased germination rate, increased root length, and enhanced growth of the seedlings.…”

“…Transverse sections of basil seeds showed remobilization of some key micro‐ and macronutrients from the cotyledons and endosperm into the embryonic radicle. [ 70 ] The authors suggest that the electric field of their VDBD promotes the element mobilization. Future characterization of the timing of this response will help clarify whether this remobilization is mediated by plant transporters.…”

Surface Dielectric Barrier Discharge plasma: a suitable measure against fungal plant pathogens

“…Among those, the atmospheric pressure low temperature plasma (LTP) represents a novel promising tool 5 . LTPs can be produced with different discharge configurations, such as corona, micro-hollow cathode, gliding arc, atmospheric uniform glow, dielectric barrier discharges, plasma jet and needle [6][7][8][9][10][11][12][13][14] .…”