Abstract:

【Objective】The objective of this experiment is to reveal the effects of phenolic substance contents and PAL, LOX activities in soybean leaves under elevated O3 concentrations, which will provide a basis at the molecular level for the adaptive mechanism of secondary metabolism in plant. 【Method】 Open-top chambers (OTCs) were utilized to investigate the effects of phenolic compounds and antioxidant ability in soybean leaves under different O3 concentration at (80±10 nmol?mol-1 and 110±10 nmol?mol-1) . 【Result】 The results indicated that, compared with control, the O3 concentration at 80±10 nmol?mol-1 induced an increase (P＜0.05) of flavonoids content, polyphenols content and the activities of phenylalanineammonialyase (PAL), lipoxygenase (LOX), polyphenol oxidase (PPO). But the O3 concentration at 110±10 nmol?mol-1 induced an decrease (P＜0.05) of flavonoids content and PAL activity. Then superoxide anion ( ) production rate, hydrogen peroxide (H2O2) content, relative electrical conductivity and malondialdehyde (MDA) content in soybean leaves increased under ozone stress. 【Conclusion】 The activities of PAL and LOX can be activated under certain extent elevated O3 concentration, which are beneficial to the accumulation of phenolic substances as to protect the normal growth and development of soybeans. But antioxidant system can not tolerate oxidative damage caused by elevated O3 concentration, thus increasing membrane lipid peroxidation, which represents injured effects on soybean.

Key words: soybean (Glycine max.), elevated O3 concentration, phenolic substances, reactive oxygen species, antioxidant ability