Growth Stimulation of Durum Wheat and Common Buckwheat by Non-Thermal Atmospheric Pressure Plasma

Abstract

The grains of durum wheat (Triticum durum Desf.) and achenes of common buckwheat (Fagopyrum esculentum Moench) were tested after treatment with two sources of non-thermal atmospheric pressure plasma (DCSBD, MSDBD) with different treatment times (0, 3, 5, 10, 20, 30, and 40 s). The effect of these treatments was monitored with regard to the seed surface diagnostics (water contact angle-WCA, chemical changes by Fourier transform infrared spectroscopy-FTIR); twenty parameters associated with germination and initial seed growth were monitored. A study of the wettability confirmed a decrease in WCA values indicating an increase in surface energy and hydrophilicity depending on the type of seed, plasma source, and treatment time. Surface analysis by attenuated total reflectance FTIR (ATR-FTIR) showed no obvious changes in the chemical bonds on the surface of the plasma-treated seeds, which confirms the non-destructive effect of the plasma on the chemical composition of the seed shell. A multivariate analysis of the data showed many positive trends (not statistically significant) in germination and initial growth parameters. The repeated results for germination rate and root/shoot dry matter ratio indicate the tendency of plants to invest in underground organs. Durum wheat required longer treatment times with non-thermal plasma (10 s, 20 s) for germination and early growth, whereas buckwheat required shorter times (5 s, 10 s). The responses of durum wheat grains to the two non-thermal plasma sources used were equal. In contrast, the responses of buckwheat achenes were more favorable to MSDBD treatment than to DCSBD.

Keywords: Fagopyrum esculentum; Triticum durum; low-temperature plasma; plasma treatment; seed; seedling.

Figure 1

Effect of NTP treatment with DCSBD and MSDBD on the WCA measured on durum wheat grains and buckwheat achenes at optimal treatment times (buckwheat: DCSBD = 10 s, MSDBD = 5 s; durum wheat: DCSBD = 20 s, MSDBD = 30 s). The droplet images are assigned to resulting WCA values in graphs using arrows.

Figure 2

ATR-FTIR spectra of buckwheat and wheat durum before (control sample) and after plasma treatment with DCSBD and MSDBD in ambient air at optimal treatment times (buckwheat: DCSBD = 10 s, MSDBD = 5 s; durum wheat: DCSBD = 20 s, MSDBD = 30 s). Peaks of characteristic functional groups are marked by numbers above the peak (assignment of numbers is in Table 1). The * at the number in spectrum of durum wheat marks the extra functional groups present only in this spectrum (to preserve the same numbering in both spectra).

Figure 3

Heatmap histogram correlation between measured characteristics and used non-thermal plasma treatments. Two plasma treatments (DCSBD and MSDBD) in various time expositions on buckwheat and durum wheat are presented. Subfigures (A–D) correspond to individual combinations between NTP type and plant species. The abbreviations of the characteristics are explained in the 4.5. Germination and Early Growth.

Figure 4

Plots of Principal Component Analysis (PCA) on measured characteristics in treated buckwheat and durum wheat by non-thermal plasma treatments (DCSBD and MSDBD) after various time expositions. Subfigures (A–D) correspond to individual combinations between NTP type and plant species. The abbreviations of the characteristics are explained in the 4.5. Germination and Early Growth.

Figure 5

Photo of the DCSBD (A) and MSDBD (B) plasma source and view of the location of the seeds in the plasma area (C,D).