Cold Plasma Treatment Effects on Corn (Zea mays L.) Yield and Iron and Zinc Concentration

IntroductionToday, it is an inevitable necessity to make use of advanced and efficient technologies in order to increase productivity and gain a better economic status. Among different methods attracted the attention of researchers for enhancement in quantity and quality yield, cold plasma technique as a modern procedure has shown a promising prospects. Despite the importance of using cold plasma in agriculture, studies have focused more on the effect of this technique on reducing microbial load in agricultural products, less on absorption of nutrients in plants. Therefore, the objectives of this experiment were to evaluate the impacts of plasma treatment of corn seeds and plasma activated water (PAW) on growth and concentration of zinc and iron in the shoots of corn. Materials and MethodsThis research was conducted as a factorial experiment based on completely randomized design (CRD) with 3 replications in a research greenhouse in agricultural and natural resources research and education center of Khorasan Razavi. The factors of experiment were three types of seed (control seeds, seeds treated with dry plasma and wet plasma), two kinds of irrigation water (distilled water and PAW) and two levels of foliar spray (without foliar spray and foliar spray with iron and zinc). Required mass of soil, was gathered, air-dried, sieved from 5 mm mesh and weighted in 6 packs. Based on the soil test values the required macro, micronutrients (except for iron and zinc) was calculated and added to the soil, and then the soil samples were moved to the pot. PLASMA BIOTEC Company located in Khorasan Razavi Park of Sciences and Technology, Mashhad, Iran performed plasma treatment of seeds and water. Plasma treated corn seeds were planted on May 18th with a density of 6 seeds in each pot. Plantlets were reduced to 2 plants after germination and establishment and irrigation was continued with desired treatments. Shoots of each pot was cut 8 weeks after sowing, 1 cm above the ground and delivered to the laboratory, where the samples were washed, dried, grounded  and the concentration of zinc and iron were measured using the atomic absorption device (Perkin Elmer, 2380) in dry ash digested in 2 N HCl acid. Data were statistically analyzed by SAS statistical software (version 9.4). Comparison of means for the main effects and interactions was performed by Tukey’s test at 5 percent confidence interval. Results and DiscussionComparison of means for the interaction effects of water × seed × foliar spray showed that the minimum concentration of iron (147.67 mg/kg) was observed in plants grown from non-treated seeds, not foliar sprayed and irrigated with non-PAW (treatment 1 in Table 7). On the other hand, plants grown from wet plasma treated seeds and received foliar spray showed the highest concentration of iron regardless of irrigation water type (treatments 10 and 12 in Table 7). Comparison of means also shows that iron concentration in plants grown from dry plasma treated seeds had no significant difference with that of non-treated seeds (treatments 1 and 5 or 2 and 6). The mean comparison results for zinc concentrations showed that the minimum value was related to plants grown from non-treated seeds, not foliar sprayed and irrigated with non-PAW (treatment 1 in Table 8). The comparison of the simple effects of the type of seed on the concentration of zinc in shoots (Table 6) showed that wet plasma seeds caused a significant increase in the concentration of zinc. However, comparison of means for the interaction effects of water × seed × foliar spray showed that the effect of plasma treatment on zinc concentration was effective only in treatments that received foliar spray (comparison of treatment 2 with 10 in table 8). Based on these results the highest zinc concentration was observed in plants grown from wet plasma seeds and received foliar spray at the same time (treatment 12 in Table 8). In addition, the comparison of treatment 1 with treatment 4 and treatment 9 with treatment 2 indicates that in order to increase the concentration of zinc in plant, plasma treatment of seeds cannot replace the foliar spray method. Comparison of means for the interaction effects of water × seed × Foliar spray showed that the minimum yield was observed in plants grown from non- treated seeds, irrigated with non- activated water and not sprayed with iron and zinc solution (treatment 1 in Table 9). However, the similar treatment which grown from wet plasma treated seeds (treatment 9), showed significantly higher yield. Dry plasma, without foliar spray and without PAW (treatment 5) had no significant priority over the control. Plants grown from seeds treated with wet plasma and without foliar spray could not significantly show more iron and zinc content over the control, while their shoot yield was higher. ConclusionBased on the findings of this study, it can be inferred that irrigation with PAW and utilizing seeds treated with dry plasma exhibited no significant impact on augmenting zinc and iron content, as well as shoot yield. Conversely, wet plasma treatment, while not yielding significant enhancements in the concentration of iron and zinc within the plant, did result in increased yield. It is crucial to note that the extent of influence exerted by factors such as frequency and duration of seed exposure to plasma conditions on the observed outcomes may vary significantly. Therefore, optimizing methodology and conducting further research in this domain are imperative for a comprehensive understanding of these processes.