Effects of Exogenous Regulating Substances on Physiological Characteristics of Erythrophleum fordii Seedlings Under Lead Stress

【Objective】This paper aims to study the effect of exogenous regulators on physiological characteristics and stress resistance of Erythrophleum fordii subjected to lead stress, and to explore the response mechanism of the plant to lead ions, so as to provide theoretical guidance for the cultivation, and introduction of and its function in restoring heavy metal contaminated soil.【Method】In this study, one-year-old seedlings of E. fordii were treated with different concentrations of betaine (BT), salicylic acid (SA), methyle jasmonate(MeJA) and calciumchloride(CaCl2), and then the seedlings were subjected to lead stress(10 mmol•L-1). The activity of antioxidant enzymes (superoxide dismutase (SOD), peroxidase (POD), catalase (CAT)), contents osmotic adjustment substances [proline (PRO), soluble sugar (SS), soluble protein (SP)], leaf cell membrane permeability [malondialdehyde (MDA), relative conductivity(RC)] and chlorophyll content (SPAD value)in E. fordii seedlings were measured.【Result】The results showed that lead stress significantly inhibited the growth of seedlings, resulting in a significant decrease in the content of osmotic adjustment substances, a significant increase in MDA content and RC, and inhibition of photosynthetic pigment synthesis. Compared with the non-stress control(CK1), the activities of SOD, POD and CAT increased by 7.0%, 1 221.6% and 121.0%, respectively. The results showed hat E. fordii seedlings had a certain resistance to lead stress. The exogenous regulators had significant effects on activating antioxidant enzymes activities, increasing PRO and SP content, reducing MDA content and RC, and promoting the synthesis of chlorophyll, but had no promotion effect on SS content. Compared with the treatments of lead stress (CK2), MeJA of 0.1 mmol•L-1 increased SOD activity by 13.2%, BT of 100 mg•L-1enhanced CAT activity by 17.7%, SA of 25 mg•L-1improved POD activity by 36.2%, MeJA of 1 mmol•L-1improved PRO content by 157.3%, BT of 1 000 mg•L-1increased SP content by 71.9%, CaCl2 of 5 mmol•L-1enhanced SPAD value by 22.9%, BT of 100 mg•L-1 decreased MDA content by 58.9%, and BT reduced the RC to some extent. Correlation analysis showed that there was a direct or indirect internal correlation between those physiological indicators. Physiological indicators promoted or antagonized each other, and regulated dynamic repair of damage by lead stress.【Conclusion】Exogenous regulators can effectively alleviate the damage of lead to E. fordii seedlings. According to its overall benefit contribution, the performance of exogenous regulators in adaptively inducting lead resistance is 1 mmol•L-1MeJA>20 mmol•L-1CaCl2>100 mg•L-1BT>5 mmol•L-1 CaCl2>0.1 mmol•L-1 MeJA>500 mg•L-1 BT>CK2. © 2021, Editorial Department of Scientia Silvae Sinicae. All right reserved.