关键词: 血皮槭, 种子休眠, 发芽抑制物, 代谢组

Abstract:

Objective: Acer griseum is a plant native to China that is endangered and also an excellent ornamental tree species. However, the seeds of A. griseum have deep physiological dormancy, which hinders its population restoration and production application. This study aims to better understand the seed dormancy mechanism of A. griseum and to find ways to alleviate dormancy, so as to provide reference for the research of seed dormancy mechanism of A. griseum and other plants and production practice. Method: The germination process of A. griseum seeds in natural condition was dynamically observed to study the natural dormancy duration. Low temperature stratification, detachment of embryos, and different concentrations of gibberellin solution were conducted to explore methods to break the dormancy of A. griseum seeds. Wheat seeds were treated with extracts from various parts of dormant A. griseum seeds, and the germination vigor, germination rate, and germination index of wheat seeds in each treatment group were analyzed to identify the location of substances that inhibited the germination of A. griseum seeds. Finally, metabolomics techniques were used to explore the specific substances that could affect the dormancy of A. griseum seeds. Result: 1) In natural condition, the dormancy duration of A. griseum seeds was approximately 29 months. Low temperature stratification for 3–12 months, detachment of embryos, and 200, 400, and 800 mg·L^–1 concentrations of gibberellin solution did not break the dormancy of A. griseum seeds. 2) Wheat seeds treated with extracts from the wings and outer seed coat of dormant A. griseum seeds had higher germination vigor and germination rate than those in the control group. Wheat seeds treated with extracts from the embryos of dormant A. griseum seeds had significantly lower germination vigor, germination rate, and germination index than those in the control group (P < 0.01). The germination vigor, germination rate, and germination index of wheat seeds treated with extracts from the dormancy-broken A. griseum seed embryos had no differences compared to those in the control group. 3) The metabolomics analysis showed that there were 289 and 215 significantly different metabolites in the dormant and dormancy-broken A. griseum seed embryos, respectively. These significantly different metabolites were matched through secondary spectra, with 146 in the positive ion mode and 109 in the negative ion mode; Among the 20 metabolites with the highest multiple of difference (|log₂FC|), 19 showed a significant decrease in content after seed dormancy was broken, mainly distributed in fatty acyl groups and benzene and its substituted derivatives. A class of significant differential metabolites, phenolic phosphates, were identified through a first-order spectra. These metabolites included fatty acyls and phenolic compounds, and they played a key role in affecting the seed dormancy of A. griseum. The substances that inhibited the seed germination of A. griseum were fatty acyl 2-hydroxyoctanoic acid, jasmonic acid, trans-2-octenoic acid, and 1, 11-undecanedicarboxylic acid of the fatty acyls and methylgingerol, xanthurenic acid, and methyl vanillate of the phenols. Conclusion: The dormancy of A. griseum seeds belongs to deep physiological embryo dormancy, with a dormancy period of about 29 months. The seed wings, outer seed coat, and inner seed coat of A. griseum have no inhibitory effect on its germination, and the seed wings and outer seed coat contain substances that promote seed germination. The substances that inhibit the germination of A. griseum seeds exist in the embryo. The dormancy of A. griseum seeds is not caused by a single endogenous substance, but may be the result of the interaction or superposition of multiple substances. Breaking the dormancy of A. griseum seeds using gibberellin may not be effective, and more research is needed to find effective methods to break the dormancy.

Key words: Acer griseum, seed dormancy, germination inhibitors, metabolomics