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Acta Prataculturae Sinica ›› 2021, Vol. 30 ›› Issue (4): 160-169.DOI: 10.11686/cyxb2020173

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Endogenous hormone responses to nitric oxide in alfalfa seedlings under PEG stress

Xiao-fang ZHANG1,2,3(), Xiao-hong WEI1,2,3(), Fang LIU1, Xue-mei ZHU1   

  1. 1.College of Life Science and Technology,Gansu Agricultural University,Lanzhou 730070,China
    2.Gansu Key Lab of Crop Improvement and Germplasm Enhancement,Lanzhou 730070,China
    3.Gansu Provincial Key Laboratory of Aridland Crop Science,Lanzhou 730070,China
  • Received:2020-04-13 Revised:2020-07-13 Online:2021-04-20 Published:2021-03-16
  • Contact: Xiao-hong WEI

Abstract:

This research studied the endogenous hormone responses to nitric oxide (NO) in leaves and roots of 50-day old alfalfa seedlings under PEG stress. Polyethylene glycol (PEG-6000) was used as the osmotic regulator to simulate drought stress. Exogenous spraying of NO releasing agent sodium nitroprusside (SNP) and NO scavenger carboxy-PTIO (cPTIO), and liquid chromatography/mass spectrometry methods were used to study the response of four endogenous hormones (abscisic acid, ABA; indole-3-acetic acid, IAA; salicylic acid, SA; gibberellin, GA3) to NO in the leaf and root systems of alfalfa seedlings under PEG stress. Treatments included in the experiment were: T1, distilled water (CK), T2, PEG added; T3, SNP+PEG added; and T4, cPTIO+PEG added. It was found that: 1) The application of exogenous NO under PEG stress (T3) can promote the NO content in the leaf and root of alfalfa, and the NO scavenger cPTIO (T4) significantly reduced the NO content in leaves of alfalfa. 2) With increasing duration of PEG stress, the levels of ABA and SA in leaves and roots increased gradually, but the ABA and SA levels in the root system increased later than those in the leaves. On the 8th day of stress, the leaf ABA content in plants of T3 was 6.68 times higher than the SA content, while the ABA content in plants of T4 was 77.22% higher than the SA content, and the leaf ABA content in leaves of T3 plants was significantly higher than that in roots. 3) NO rapidly induces an increase in the IAA and GA3 concentrations in leaves and roots. On the 4th day of stress, the IAA levels in leaves under exogenous NO treatment were 1.65 times higher than in the cPTIO scavenger treatment. Meanwhile the IAA concentration in roots was 8.70% higher in T4 than T3, and the GA3 content in leaves and roots of T3 was 54. 49% and 84. 65% higher, respectively, than in T4. GA3 content reached its maximum on the second day of treatment and decreased thereafter. In summary, NO is here shown to regulate the growth and stress resistance of alfalfa plants by raising or lowering the metabolic levels of IAA, ABA, GA3 and SA, the regulation of ABA and SA in alfalfa is particularly prominent.

Key words: Medicago sativa, PEG stress, nitric oxide, endogenous hormone