Effect of Low-Pressure Radio Frequency Plasma on Ajwain Seed Germination

Abstract

In this article, we study the effect of low-pressure radio frequency (RF) plasma on seed germination and growth of the ajwain plant. Ajwain seed is a medicinal plant that possesses antibacterial and antioxidant properties. Results show that RF plasma treatment of ajwain seed improves seed germination rate by ~11%. The best result was observed at a plasin seed wettability and plant growth parameters including shoot and root length improvement after plasma treatment.

Biochemical and Physiological Plant Processes Affected by Seed Treatment with Non-Thermal Plasma

“…As shown in Table 1 , the effects of seed treatment using different NTP devices and protocols have been extensively studied in a wide variety of plants including the main strategic crops (such as wheat, corn, legumes, and oilseeds). Stimulating effects of seed treatment on seed germination in vitro have been demonstrated in most of the publications [ 37 , 41 , 42 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 , 58 , 59 , 60 , 61 , 62 , 63 , 64 , 65 , 66 , 67 , 68 , 69 , 70 , 71 , 72 , 73 , 74 , 75 , 76 , 77 , 78 , 79 , 80 , 81 , 82 , 83 , 84 , 85 , 86 , 87 , 88 , 89 , 90 , 91 , 92 , 93 ,…”

Entering the plasma agriculture field: An attempt to standardize protocols for plasma treatment of seeds

“…This process is repeated for the available plasma parameters, although it is not practical to vary every parameter in Sections 3 and 5. The most convenient variables to be scanned are those in Section 5, namely, plasma treatment time, [9,23,24,27,30,33,35,38,39,[39][40][41]48,[55][56][57]62,69,75,77,78,81,85,92,94,95,99,116,117] voltage or power, [19,22,23,59,78,[82][83][84]86,89,92,118] flow rate, [119] or gas type and mixture. [24,30,36,77,89,92,118] More rarely studied are the excitation frequenc...…”

“…Low-pressure RF plasmas, heated by a continuous oscillating electron current, [93] feature standard excitation frequencies of, for example, 5.28 MHz [79][80][81]127] or the common industrial, scientific, and medical standard frequency of 13.56 MHz. [28,77,78,[82][83][84][86][87][88][89]117,120] A microwave plasma torch used a 2.45 GHz power supply, [119] and gliding arc discharges have been explored at 50 Hz. [9,76] Voltage and current: The discharge peak voltage values in DBDs depend on the gas mixture, pressure, and discharge gap.…”

“…As a rule of thumb, seeds placed on an electrode are nominally in direct contact with the plasma, as in a VDBD, an SDBD (except for the lateral nonuniformity in Figure 4), [21,45,47,[55][56][57][58] or an RF capacitively coupled reactor. [82,83,120] This proximity to the plasma leads to the most heating, the strongest etching via ion bombardment, and the highest concentration of reactive radicals and UV radiation. If the seed substrate is separate but placed closely parallel to an SDBD, so that the seeds are approximately within the plasma glow, this results in a weaker form of direct contact.…”

“…The mechanisms of plasma-seed treatments as a potential seed processing technology are reviewed by Waskow et al, [14] and some of the corresponding plasma devices found in the literature are listed in Figure 3. Among the papers cited in the present study, the most common plasma sources include planar dielectric barrier discharges (DBDs) in various forms as shown in Figure 3(1), followed by DBD plasma jets as shown in Figure 3(2) [10,36,[65][66][67][68][69][70][71][72][73][74] ; low-pressure plasma in a vacuum chamber as shown in Figure 3(3) [28,43,[75][76][77][78][79][80][81][82][83][84][85][86][87][88][89] ; and less common devices such as gliding arcs, [9,43,76,90] and corona arrays as shown in Figure 3(4). [43,91,92] The various types of plasma sources in Figure 3 can be summarized as follows: A DBD generates plasma by timevarying high voltage (kV) between two electrodes; the dielectric barrier is to prevent arcing between electrodes that could otherwise occur following the electrical breakdown of the gas.…”