Silicon promotes growth and root yield of Glycyrrhiza uralensis under salt and drought stresses through enhancing osmotic adjustment and regulating antioxidant metabolism

Abstract

Silicon promotes beneficial effects that improve plant tolerance to salt and drought stresses though the mechanisms that cause these effects remain poorly understood. Glycyrrhiza uralensis Fisch. ex DC. (G. uralensis) is an important Chinese herb plant of the family Leguminosa. In this study, pot experiments were conducted to investigate the long-term effects of silicon on growth and physio-biochemical characteristics of two-year-old G. uralensis subjected to salt and drought stresses. The results showed that all stress treatments decreased G. uralensis growth and this adverse effect was reversed by addition of silicon. Added silicon also affected physio-biochemical characteristics of G. uralensis, and these effects varied depending on levels of salt and drought stresses and the developmental stages of the studied plants. Silicon reduced Na+ content and correspondingly increased K+/Na+ ratio. Silicon also increased soluble sugar and proline contents under salt combined drought stress respectively at 110 days and increased soluble protein content under all stress treatments at 70 days. Silicon increased catalase and ascorbate peroxidase activities under all stress treatments. Silicon also increased glutathione reductase activity, which was accompanied by increasing glutathione content under salt combined drought stress. These changes caused decrease of reactive oxygen species, malondialdehyde content and membrane permeability correspondingly. In sum, silicon benefited alleviation of osmotic and oxidative stresses induced by salt and drought stresses on G. uralensis mediated by regulating osmolytes to improve water status and antioxidants to maintain membrane stability.