血皮槭种子休眠特性及休眠原因

Characteristics and Mechanism of Seed Dormancy of Acer griseum

【目的】血皮槭种子存在深度生理胚休眠,制约其种群恢复和生产应用。探究血皮槭种子休眠机制,寻求解除休眠的方法,可为血皮槭及其他植物的种子休眠机制研究和生产实践提供参考。【方法】对血皮槭种子自然状态下萌发过程进行动态观测,研究其自然休眠时长;通过3~12个月低温层积、切离胚以及不同浓度赤霉素溶液处理,探寻打破血皮槭种子休眠的方法;利用休眠的血皮槭种子各部分浸提液处理小麦种子做发芽试验,分析各处理组小麦种子的发芽势、发芽率和发芽指数,分析血皮槭种子中抑制其萌发的物质存在部位;通过代谢组技术,探究影响血皮槭种子休眠的具体物质。【结果】1)自然状态下,血皮槭种子休眠时间约为29个月;血皮槭种子经3~12个月的低温层积、切离胚和200、400、800 mg·L^(–1)浓度的赤霉素溶液处理均不能打破休眠。2)休眠血皮槭种子的种翅和外种皮浸提液处理的小麦种子发芽势和发芽率高于对照组;休眠血皮槭种子种胚浸提液处理的小麦种子发芽势、发芽率和发芽指数显著低于对照组(P<0.01);打破休眠的血皮槭种子种胚浸提液处理的小麦种子发芽势、发芽率和发芽指数显著高于休眠的种子种胚浸提液处理组。3)血皮槭休眠的种子种胚和打破休眠的种子种胚中显著差异代谢物分别为289个和215个,通过二级谱图匹配这些显著差异代谢物在正离子模式下有146个,负离子模式下有109个;差异倍数(|log2FC|)最大的20个代谢物中,有19个在种子打破休眠后含量显著减少,它们主要分布在脂肪酰基类和苯及其取代衍生物类中;通过一级谱图,定性了一类显著差异代谢物——酚磷酸;脂肪酰基类和酚类代谢物在影响血皮槭种子休眠中起关键作用,抑制血皮槭种子发芽的物质是脂肪酰基类的2-羟基辛酸、茉莉酸、反式-2-辛烯酸和十三碳二元酸,以及酚类的甲基生姜酚、黄尿酸、香草酸甲酯。【结论】血皮槭种子休眠属于深度生理胚休眠,休眠时间约为29个月;血皮槭种子的种翅、外种皮和内种皮对其萌发没有抑制作用,且种翅和外种皮中含有促进种子发芽的物质;抑制血皮槭种子发芽的物质存在于种胚中;血皮槭种子休眠并不是单一的内源性物质造成的,可能是多种物质的互作或者叠加的结果。

【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.