Exogenous Spermidine Priming Mitigates the Osmotic Damage in Germinating Seeds of Leymus chinensis Under Salt-Alkali Stress

Chen Hongna; Shi Junmei; Tao Leyuan; Han Xiaori; Lin Guolin; Cheng Xianguo

doi:10.3389/fpls.2021.701538

Exogenous Spermidine Priming Mitigates the Osmotic Damage in Germinating Seeds of Leymus chinensis Under Salt-Alkali Stress

Front Plant Sci. 2021 Oct 13:12:701538. doi: 10.3389/fpls.2021.701538. eCollection 2021.

Authors

Chen Hongna^{1

2}, Shi Junmei², Tao Leyuan¹, Han Xiaori², Lin Guolin², Cheng Xianguo¹

Affiliations

¹ Laboratory of Plant Nutrition and Biology, Institute of Agricultural Resources and Regional Planning, Chinese Academy of Agricultural Sciences, Beijing, China.
² College of Land and Environment, Shenyang Agricultural University, Shenyang, China.

Abstract

Spermidine (Spd) is known to protect macromolecules involved in physiological and biochemical processes in plants. However, it is possible that Spd also plays an osmotic regulatory role in promoting the seed germination of Leymus chinensis (L. chinensis) under salt-alkali stress. To investigate this further, seeds of L. chinensis were soaked in Spd solution or distilled water, and a culture experiment was performed by sowing the soaked seeds in saline-alkaline soils. The data showed that the Spd priming resulted in an increase of more than 50% in soluble sugar content and an increase of more than 30% in proline content in the germinating seeds. In addition, the Spd priming resulted in an increase of more than 30% in catalase activity and an increase of more than 25% in peroxidase activity in the germinating seeds and effectively mitigated the oxidative damage to the plasma membrane in the germinating seeds under salt-alkali stress. Moreover, the Spd priming of seeds affected the accumulation of polyamine (PA) and maintained the activities of macromolecules involved in physiological metabolism in germinating seeds exposed to salt-alkali stress. Furthermore, the Spd priming treatment increased the hydrogen peroxide (H₂O₂) level to more than 30% and the Ca²⁺ concentration to more than 20% in the germinating seeds, thus breaking the dormancy induction pathways in L. chinensis seeds through beneficial hormone enrichment. This study provides an insight into the Spd-mediated regulation pathway during exogenous Spd priming of L. chinensis seeds, which mitigates osmotic and oxidative damage and maintains the integrality of the cell lipid membrane. Thus, exogenous Spd priming increases PA oxidase activity and maintains the accumulation of H₂O₂. We found that the H₂O₂ beneficially affected the balance of Ca²⁺ and hormones, promoting the vigor and germination of L. chinensis in response to salt-alkali stress.

Keywords: Leymus chinensis; germination; polyamine oxidase; salt-alkali stress; spermidine.