Germination improvement of fenugreek seeds with cold plasma: Exploring long-lasting effects of surface modification

Abstract

Pre-sowing cold plasma (CP) treatment of seeds is a proven method for enhancing seed germination and plant growth. This paper presents a study on the long-lasting effects of CP treatment on fenugreek (Trigonella foenum-graecum) seeds to elucidate the basic mechanism of plasma action and pave the way for future field experiments. The seeds were subjected to short-duration treatments (10 and 20 s) using the kINPen 11 plasma jet and then stored for 3 months before sowing. After this period, the treated seeds exhibited higher germination efficiency, and the resulting seedlings were longer and more vigorous compared to normal seedlings. The improvement in germination was particularly noticeable for a treatment time of 20 s. Although we observed the age-related hydrophobic recovery, the plasma-treated seeds consistently showed better wettability than the control group. However, no direct correlation was found between wettability and germination improvement. Scanning electron microscopy (SEM) analysis revealed increased surface roughness and microstructuring of the outer layers of the seed coat after plasma treatment, while X-ray photoelectron spectroscopy (XPS) indicated an increase in the O/C ratio, as well as the presence of calcium and potassium. These findings suggest that the argon plasma etched the uppermost layer of the seed coat, leading to structural changes. It is suspected that the observed faster germination and growth of plasma-treated seeds is seeds due to these long-lasting changes in the seed coat structure, which may disrupt its tissues and open access to the interior of the seed. Under appropriate conditions, this facilitates an increase in the metabolic activity of the embryo. Such a mechanism can be considered as plasma scarification of the seed. This study highlights the potential of cold plasma technology as a viable and simple strategy for improving seed germination and plant growth in the long term, with important implications for the agricultural sector.