Abstract:

Hormone content in Peaonia ostti‘Fengdan’seeds from 8 stages after sowing under 25 ℃ and 4 ℃ treatments was analyzed by ultra-performance liquid chromatography/tandem mass spectrometric（UPLC-MS/MS）method. Four signal transduction genes expression（PoGID1a，PoGAMYB4，PoGAI and PobZIP）were tested by qRT-PCR. The results showed that‘Fengdan’seeds could germinate under 25 ℃ treatment，while it could not germinate within 100 days after sowing（DAS）under 4 ℃ treatment. The GA₃ content increased first and then decreased under two treatments，while it was significantly higher in seed at 17 DAS（seed hypocotyls germination stage）under 25 ℃ treatment than that under 4 ℃ treatment. The ABA content decreased continuously under 25 ℃ treatment，while it increased rapidly after a short period decrease under 4 ℃ treatment，and it was significantly higher than 25 ℃ treatment at 7–17 DAS. It was deduced that the high level of GA₃ content at 17 DAS under 25 ℃ treatment could promote seed germination and the high level of ABA content under 4 ℃ treatment inhibited seed germination. The expression patterns of PoGID1a and PoGAI under 25 ℃ and 4 ℃ treatments showed an up-to-down trend，while the expression level of PoGID1a and PoGAI（21 d excluded）were higher and lower，respectively under 25 ℃ treatment than that under 4 ℃ treatment. The expression pattern of PoMYB4 showed an increasing trend under 25 ℃ treatment，while it increased slightly at the initial stages and then decreased under 4 ℃ treatment. On the whole，the expression level of PoMYB4 under 25 ℃ treatment was significantly higher than that under 4 ℃ treatment，at 3–100 DAS. The expression pattern of PobZIP was similar to ABA content change，and it was significantly higher under 4 ℃ treatment than that under 25 ℃ treatment. Therefore，it was suggested that seed germination was controlled by GA and ABA. GA promoted seed germination by positively regulating GA signal ，while ABA inhibited seed germination by positively regulating ABA signal transduction PobZIP expression.transduction PoGID1a and PoGAMYB4 and negatively regulated PoGAI

Key words: tree peony, Peaonia ostii, low temperature, GA, ABA, signal transduction, seed germination