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Acta Prataculturae Sinica ›› 2023, Vol. 32 ›› Issue (8): 141-151.DOI: 10.11686/cyxb2022252

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Nitric oxide regulation of secondary metabolite accumulation in Medicago sativa seedlings under drought stress

Bao-qiang WANG1,2,3(), Wen-jing MA1(), Xian WANG1,4, Xiao-lin ZHU1,4, Ying ZHAO1,2,3, Xiao-hong WEI1,2,3,4()   

  1. 1.College of Life Science and Technology,Gansu Agricultural University,Lanzhou 730070,China
    2.Gansu Key Laboratory of Crop Improvement & Germplasm Enhancement,Lanzhou 730070,China
    3.Gansu Provincial Key Laboratory of Aridland Crop Science,Lanzhou 730070,China
    4.College of Agronomy,Gansu Agricultural University,Lanzhou 730070,China
  • Received:2022-06-16 Revised:2022-10-19 Online:2023-08-20 Published:2023-06-16
  • Contact: Xiao-hong WEI

Abstract:

The aim of this study was to determine the effects of nitric oxide (NO) on the accumulation of metabolites and the activities of key metabolic enzymes in leaves and roots of drought-stressed alfalfa (Medicago sativa). The NO donor sodium nitroprusside and the NO scavenger carboxy-2-phenyl-4,4,5,5-tetramethylimidazolineoxyl-l-oxyl-3-oxide (c-PTIO) were applied as foliar sprays to potted alfalfa plants under simulated drought conditions (using polyethylene glycol-6000). The contents of total phenols, flavonoids, lignans, and anthocyanins increased and then decreased in the leaves and roots of alfalfa during the drought treatment, while the activities of phenylalanine aminolytic enzymes and polyphenol oxidase increased. These trends were promoted by application of exogenous NO, which increased the total phenolic content by 33.08% and led to higher phenolic contents during the late stages of drought stress, thereby reducing drought-induced damage. In contrast, application of the NO inhibitor c-PTIO inhibited the accumulation of phenolic compounds and reduced the activity of key metabolic enzymes in drought-stressed alfalfa seedlings. Thus, exogenous NO promoted the accumulation and retention of secondary metabolites and increased antioxidant enzyme activity in alfalfa to levels higher those under drought stress alone. This greatly reduced the severity of drought damage in alfalfa plants, and improved their drought tolerance. These findings improve our understanding of the plant response to drought stress, and highlight the potential use of an NO donor as a tool to improve the drought tolerance of alfalfa.

Key words: nitric oxide, drought stress, alfalfa, secondary metabolite