Comparative study on growth, physiological and biotic stress resistance of cucumber (Cucumis sativus L.) by exogenous application of jasmonic acid and methyl jasmonate under greenhouse conditions

Abstract JA is a defensive plant hormone, and its derivative MeJA is widely used in scientific research as an exogenous plant regulator to plants under biotic or abiotic stress. In recent years, the comparative study of MeJA and JA has become a new field for JA researchers, but most of them remain in laboratory experiments. Differences between the response of JA compounds to biotic stress in crops under greenhouse conditions, is not studied well. In this study, we studied the difference of two JA compounds in the regulation of physiological, growth and biotic stress resistance of cucumber under greenhouse conditions. We have three key findings: (1) JA compounds can significantly enhance the antioxidant activity, defense secondary metabolite accumulation and stress-resistance of cucumber. (2) MeJA increased the accumulation of lignin in cucumber leaves by elevating the activities of enzymes related to lignin biosynthesis (PAL, POD, LAC), which resulted in lower value of plant stress rating than JA. (3) MeJA also had a greater limiting effect on cucumber biomass accumulation than JA, which may be another reason for the lower plant stress rating. Our research has provided suggestions and experience for relevant agricultural production and follow-up scientific research.