Vermicompost improves the physiological and biochemical responses of blessed thistle (Silybum marianum Gaertn.) and peppermint (Mentha haplocalyx Briq) to salinity stress

In this study, we examined whether vermicompost enhances a plant's tolerance to salinity. We analyzed the physiological responses of the aerial parts and roots of the herbal stress-resistant plants blessed thistle and peppermint with NaCl and cow manure vermicompost and inorganic fertilizer. Salinity greatly enhanced the accumulation of malondialdehyde (MDA) and proline in the aerial parts and roots of the two species, but did not affect chlorophyll content. The K+/Na+ and Ca2+/Na+ ratios and the total soluble protein content were decreased in the aerial parts and roots under salinity conditions in both species. Under normal conditions, vermicompost enhanced plant growth and increased the K+/Na+ and Ca2+/Na+ ratios and total soluble protein content while inorganic fertilizer treatment increased the total soluble protein content and proline content in both species. Proline content in both species was greatly decreased under vermicompost treatment than inorganic treatment under normal conditions. Furthermore, under high salinity conditions, vermicompost treatment significantly reduced the MDA content and increased total soluble protein content and the K+/Na+ and Ca2+/Na+ ratios than stress-treated plants. Vermicompost had complex effects on the antioxidant enzyme activities of plants grown under high salinity treatment. Our results show vermicompost mitigates the effects of salinity stress.