Mechanisms and Signaling Associated with LPDBD Plasma Mediated Growth Improvement in Wheat

This study investigates the effect and mechanisms of low pressure dielectric barrier discharge (LPDBD) produced with Ar/O₂ and Ar/Air technique causing biological stimulation leading to improved germination and growth in wheat. Both plasma treatments caused rougher and chapped seed surface along with noticeable improvement in seed germination in wheat. Beside this, seed H₂O₂ concentration significantly increased compared to controls subjected to Ar/O₂ and Ar/Air while this phenomenon was more pronounced due to Ar/Air plasma. Analysis of plants grown from the plasma treated seeds showed significant improvement in shoot characteristics, iron concentration, total soluble protein and sugar concentration in comparison with the controls more efficiently due to Ar/O₂ plasma than that of Ar/Air. Further, none of the plasma treatments caused membrane damage or cell death in root and shoot of wheat. Interestingly, Ar/O₂ treated plants showed a significant increase (2-fold) of H₂O₂ compared to controls in both root and shoot, while Ar/Air plasma caused no changes in H₂O₂. This phenomenon was supported by the biochemical and molecular evidence of SOD, APX and CAT in wheat plants. Plants derived from Ar/O₂ treated seeds demonstrated a significant increase in SOD activity and TaSOD expression in roots of wheat, while APX and CAT activities along with TaCAT and TaAPX expression showed no significant changes. In contrast, Ar/Air plasma caused a significant increase only in APX activity in the shoot. This suggests that Ar/O₂ plasma caused a slight induction in H₂O₂ accumulation without triggering the H₂O₂ scavengers (APX and CAT) and thus, efficiency affect growth and development in wheat plants. Further, grafting of control and Ar/O₂ treated plants showed a significant increase in shoot biomass and H₂O₂ concentration in grafts having Ar/O₂ rootstock regardless of the type scion attached to it. It indicates that signal driving Ar/O₂ plasma mediated growth improvement in wheat is possibly originated in roots. Taken together, this paper delivers new insight into the mechanistic basis for growth improvement by LPDBD technique.