Abstract: Oat （Avena sativa L.） is an important forage in the world, and its growth is affected by water stress and hormone metabolism regulation. In this study, polyethylene glycol 6000 （PEG-6000） was used to simulate moderate drought（15% PEG）and severe drought（25% PEG）,and 0.5 and 1 mmol·L^-1 γ-aminobutyric acid （GABA）were sprayed at the seedling stage of oats under different drought stresses, respectively. The aims were to investigate the effects of exogenous GABA on the growth and chlorophyll fluorescence characteristics of oat seedlings under drought stress. The results showed that：（1）with the aggravation of drought,the plant height,leaf length,leaf width,root length and aboveground biomass of oat seedlings decreased,especially under severe drought stress（P<0.05）,while the leaf length,leaf width,root length and aboveground biomass of oats increased significantly after foliar application of GABA（P<0.05）；（2）drought stress led to the decrease of chlorophyll content,PSII actual photoenergy conversion efficiency（Fv'/Fm'）,photochemical quenching coefficient（qP）and PSII electron transport rate（ETR）and increase the percentage of antenna thermal dissipation percentage （Hd）of oat seedlings,on the contrary,the total amount of chlorophyll,Fv'/Fm',qP,ETR and Hd increased significantly after foliar application of GABA,especially under severe drought stress（P<0.05）,the effect of 1 mmol·L^-1 application is most pronounced；（3）correlation analysis showed that aboveground biomass per plant（ABP）was significantly positively correlated with Fm',Fv'/Fm'（P<0.05）,while root-shoot ration（R-SR） was negatively correlated with Hd（P<0.05）.Therefore,in the case of drought,GABA can be sprayed to alleviate the inhibition of drought on the photosynthesis and growth of oat seedlings.

Key words: γ-aminobutyric acid, Drought stress, Oats, Seedling growth, Chlorophyll fluorescence parameters

摘要： 燕麦（Avena sativa L.）作为一种世界性的重要饲草,其生长受到水分胁迫的影响和激素代谢调节。本研究利用PEG-6000模拟了中度干旱（15%）和重度干旱（25%）,在不同干旱胁迫下于燕麦幼苗期喷施0.5和1 mmol·L^-1 γ-氨基丁酸（γ-aminobutyric acid,GABA）,探究外源GABA对干旱胁迫下燕麦幼苗生长和叶绿素荧光特性的影响。结果表明：（1）随干旱程度的加剧,燕麦幼苗的株高、叶长、叶宽、根长和地上生物量呈降低趋势,特别是重度干旱胁迫下显著降低（P<0.05）,叶面喷施GABA后,燕麦的叶长、叶宽、根长和地上生物量则得到了显著提高（P<0.05）；（2）干旱胁迫导致燕麦幼苗叶绿素含量、PSⅡ实际光能转换效率（Fv'/Fm'）,光化学猝灭系数（Photochemical quenching coefficient,qP）和PSⅡ电子传递速率（Electron transport rate,ETR）的降低和天线热耗散百分率（Antenna thermal dissipation percentage,Hd）的升高,相反,叶面喷施GABA后,尤其是重度干旱胁迫下,叶绿素总量,Fv'/Fm',qP,ETR,Hd均显著增加（P<0.05）,其中1 mmol·L^-1的影响最为明显；（3）相关性分析表明,地上部生物量（Aboveground biomass per plant,ABP）与Fm',Fv'/Fm'呈显著正相关（P<0.05）,根冠比（Root-shoot ratio,R-SR）却与之相反,两者均与Hd呈显著负相关（P<0.05）。因而,燕麦在遭受干旱的情况下,可以喷施GABA可以缓解干旱对燕麦幼苗光合和生长的抑制作用。

关键词: γ-氨基丁酸, 干旱胁迫, 燕麦, 幼苗生长, 叶绿素荧光参数