Exogenous silicon relieve drought stress and salt stress of Glycyrrhiza uralensis seedlings by regulating proline metabolism and nitrogen assimilation

Abstract

ABSTRACT This article studies the effect and mechanism of Si on drought and salt tolerance of Glycyrrhiza uralensis by focusing on the pathways of proline metabolism and nitrogen assimilation. G. uralensis was analysed under control, 70 mM NaCl, 15% PEG-6000 and 70 mM NaCl+15% PEG-6000 with or without Si. The results showed that Si increased P5Cs and δ-OAT activities by 16.29% and 5.85% under drought-salt stress, respectively. Si increased PDH by 28.14% under salt stress and increased proline by 27.6% and 33.0% under drought and drought-salt stresses in proline metabolism. In addition, Si increased NO3 − by 36.9%, 42.63% and 44.07% under drought, salt and drought-salt stresses, respectively, increased GOGAT by 50.9% under salt stress, increased GDH by 34.78% and 25.44% under salt and drought-salt stresses in the process of N assimilation. Moreover, Si decreased H2O2 and MDA contents by 15.27%, 15.57%, 25.18% and 43.05%, 7.59%, 21.44% under drought, salt and drought-salt stresses, respectively. In sum, Si could increase the proline content by increasing P5Cs activity; meanwhile, Si also regulated the synthesis pathway of proline by improving N assimilation. Thus, the tolerance of G. uralensis to drought-salt stress was further enhanced by eliminating excessive ROS and reducing lipid peroxidation impairment.