Sound waves increases the ascorbic acid content of alfalfa sprouts by affecting the expression of ascorbic acid biosynthesis-related genes

Previous studies have shown that sound wave treatment can affect the expression of plant genes and improve the growth. So, we investigated the ability of sound waves to increase AsA (l-ascorbic acid) content in alfalfa (Medicago sativa) sprouts in this study. Sprouts were exposed to a range of sound wave frequencies for two 1-h periods per day for various numbers of days. Most sound wave treated sprouts had a higher AsA content than untreated sprouts. In addition, the activity level of superoxide dismutase, an enzyme with potent antioxidative properties, was increased in sound wave-treated sprouts. The AsA content varied in response to sound wave treatment. Most processing conditions, including 500 and 1000 Hz, increased AsA content by 24-50%; however, some treatment conditions caused reduced AsA content during sprout growth. Furthermore, AsA content during sprout storage was increased by most sound wave treatment conditions, with 13-36% increases observed following 800 and 1000 Hz sound wave treatments compared to untreated sprouts. To investigate the mechanisms underlying changes in AsA content, we analyzed the expression levels of AsA biosynthesis-related genes. We found that several genes, including VTC1, VTC2, VTC4, GME, L-GalDH, GLDH, MDHAR, and DHAR1, displayed differential expression in response to sound wave treatment. Therefore, sound wave treatment may be a viable method for increasing the nutritional contents of sprouted vegetables.