Wheat seed vigor and seedling physiology using dielectric barrier discharge plasmas

Wheat production cannot fully meet the ever-increasing growth rate of the demand in recent years. It is of great practical significance to improve the seed quality and crop growth for high wheat yield. Currently, the commonly-used methods include the seed soaking with chemical reagent, field application of fertilizer and pesticide after seeding, and genetic improvement of crops. But all of them have some limitations. Therefore, a green and safe physical technology is required to improve the seed vigor and crop growth in production. Fortunately, dielectric barrier discharge (DBD) low-temperature plasma has been used to promote the germination and growth of vegetable seeds, particularly in the degradation of mycotoxins in agricultural products. However, little has been reported on the role in the quality of wheat seeds. This study aims to reveal the direct effects of low-temperature plasma treatment on the wheat seed vigor and seedling physiology. Jimai 22 and Bainong 307 were treated by DBD low-temperature plasma with argon as gas source. A systematic investigation was made to explore the effects of different treatment times (0, 6, 9, 12, and 15 s) on seed germination and seedling growth, morphological structure of seed coat, metabolic physiology and antioxidant activity of seedlings. The results showed that the DBD low-temperature plasma treatment significantly increased the germination rate of wheat seeds, seedling root length, fresh dry weight and vigor index. The water absorption rate of wheat seeds increased under all treatment time conditions. The water absorption of wheat seeds increased by 6.4% (Jimai 22) and 5.9% (Bainong 307), respectively (P<0.05), when the treatment time was 9 s. The contact angles of wheat seeds decreased gradually with the increase of treatment time, indicating the increasing wettability of wheat seed. Once treated for 9 s, the structure of seed coat was blurred with the outstanding cracks. There was the increase in the content of photosynthetic pigments and soluble proteins in the newborn seedlings of wheat seeds after treatment. The total chlorophyll contents in the seedlings significantly increased by 7.1% (Jimai 22) and 11.4% (Bainong 307) at the treatment time of 9 s, respectively, while the contents of soluble protein in the seedlings increased the most, when the treatment time was 12 s. There was the higher antioxidant capacity of the newborn seedlings of wheat seeds after treatment. The contents of malondialdehyde in the wheat seedlings decreased by 15.6% (Jimai 22) and 18% (Bainong 307), respectively (P<0.05), when the treatment time was 9 s. Therefore, DBD low-temperature plasma was effectively improved the wheat seed vigor and the seedling physiological properties. A potential seed enhancement can be achieved in the seed quality and subsequent wheat growth in crop production.