Effect of green technologies of cold plasma and airborne ultrasound wave on the germination and growth indices of cumin (Cuminum cyminum L.) seeds

Current research is considered to study the effect of nonthermal physical field technologies of atmospheric cold plasma (CP) and ultrasound waves (US) on the germination and seedling indices of cumin seeds. In this regard, different drying strategies were planned in a single and combined form using a lab-scale cold plasma unit and ultrasound-assisted air dryer. Various duration of CP pretreatment (CPt: 0, 15, and 30 s), ultrasound power (P: 0, 60, 120, and 180 W), and air temperature (T: 30, 35, and 40 degrees C) were practiced to investigate the changes in germination traits and microstructure characteristics of cumin seeds. It was found that CP pretreatment and ultrasound treatment in a single form significantly increased germination percentage, germination index, and germination rate as well as seeding vigor of cumin seeds. The morphological alteration in the surface of the seeds, which modifies the seed surface hydrophilicity and accelerates water uptake, may be the leading cause of CP and US-induced modification in the germination power. The highest stimulatory effect belonged to the combined application of cold plasma and ultrasound wave when the cumin seeds were treated with an appropriate CP dose and ultrasound energy. So that, the maximum germination percentage (92%), germination index (14.91), and germination rate (21.33%), as well as the highest values of seedling vigor index I (178.67 mm) and vigor index II (420.72 mg), were in possession of pretreatment with CPt: 15 s before ultrasound-assisted drying at T <= 35 degrees C and P <= 120 W. Practical Applications This study demonstrates the potential of cold plasma and ultrasound wave before and during air drying of cumin seeds, respectively. Cold plasma was used as a nonthermal and nonchemical pretreatment strategy before air drying of cumin seeds in ultrasound-assisted dryer. A single application of cold plasma caused a significant increase in germination percentage, germination index, and germination rate of cumin seeds. The positive effect of cold plasma on the studied parameter of cumin seeds intensified when it was supported by airborne low-power ultrasound waves during air drying.