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Keywords
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cold plasma, cumin seeds, germination indices, growth characteristics, ultrasound
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Abstract
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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 40C) 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 USinduced
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 ≤ 35C and P ≤ 120 W.
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