Abstract: Panicum virgatum L.,Paspalum notatum Flugge,Paspalum dilatatum Poir,×Festulolium Asch et Graebn.,Phalaris arundinnaceaL.and Lolium perenne L.are important forage grasses but their productivity are often limited by the summer drought stress in most areas of China.There are research evidences showing these six species differ in their growing traits and production performance under drought stress;however research is lacking to understand the response of ultrastructure of mesophyll cells to water stress in different plant species,which is highly relevant to the mechanism of plant drought tolerance.In order to provide morphological and physiological indications for selection,introduction and breeding of the species,the effect of water stress on the ultrastructure and physiological function of chloroplast and mitochondria in mesophyll cells in the six grass species were studied under pot culture conditions using transmission electron microscope(TEM) and measurement of the chlorophyll content and net photosynthetic rate,respectively.The results showed that,after 8 d water stress,the chloroplasts swelled,became round,and moved towards the center of the cell.Some plastoglobulis and starch grains were found inside the chloroplasts.Grana and envelope in severely affected chloroplasts were disrupted.The mitochondria had better tolerance to water stress than chloroplasts and the number of mitochondria increased under water stress.The net photosynthetic rate was closely related to the change in chloroplast structure.The six grass species were classified into three groups with different tolerance to water stress: P.virgatum and Pa.notatum as the high tolerant,×Festulolium and Ph.arundinnacea as the medium tolerant,and Pa.dilatatum and L.perenne as the poor tolerant.

Key words: Gramineous grass, Water stress, Chloroplast, Mitochondria, Ultrastructure, Net photosynthetic rate

摘要： 利用透射电镜技术,研究了水分胁迫下柳枝稷(Panicum virgatum L.)、巴哈雀稗(Paspalum notatum Flugge)、毛花雀稗(Paspalum dilatatum Poir)、羊茅黑麦草(×Festulolium Asch.et Graebn.)、草芦(Phalaris arundinnacea L.)及多年生黑麦草(Lolium perenne L.)6种禾本科牧草叶肉细胞叶绿体和线粒体超微结构的变化,并结合对叶绿素含量和光合速率的测定,分析了其生理功能对水分胁迫的响应,旨在为耐旱草种的选择、引种和选育提供形态学和生理学依据。结果表明,经过8 d水分胁迫后,6种牧草的叶绿体均膨大变圆并向细胞中央移动;叶绿体内分布有一定数量的嗜锇颗粒和少量淀粉粒,受伤害严重的叶绿体中的基粒和被膜破损;线粒体数目均增加,且对水分胁迫的耐受性强于叶绿体;光合速率的高低与叶绿体的结构变化相关。可将6种牧草分为3个不同的抗旱等级:柳枝稷和巴哈雀稗抗旱性较强,羊茅黑麦草和草芦抗旱性中等,多年生黑麦草和毛花雀稗抗旱性较弱。

关键词: 禾草, 水分胁迫, 叶绿体, 线粒体, 超微结构, 净光合速率