摘要：
[Objective] Cotton seedlings are predisposed to chilling injury,and proper low-temperature pretreatment may improve the cold tolerance.The aim of this study is to analyze the effects of 12 °C cold acclimation to 4 °C cold tolerance by observing the leaf cell ultrustructure of Jinmian 49 and Keneng 0518 cotton seedlings.[Method] Cotton seeds of the two varieties were delinted and soaked for appropriate time,then cultured at 28 °C/12 h lighting condition.At stage of euphylla,half of the seedlings were placed at 12 °C/12 h lighting acclimation for 5 days,leaving the others as control (non-cold acclimation);Then all placed at 4 °C/12 h lighting treatment for 5 days,and leaf cell ultrastructure were observed and compared.[Result] In the 4 °C cold tolerance process,Jinmian 49 and Keneng 0518 with cold acclimation at 12 °C for 5 days kept better chloroplast,accumulated starch grain and high electron absorbing material;Keneng 0518 also kept integrated nucleus membrane,congregated arrangement of mitochondrion,tubular or bubbly endoplasmic reticulum.[Conclusion] These results indicated that cotton seedlings could adapt to 4 °C cold tolerance through better chloroplast,accumulating starch grain and high electron absorbing material after 12 °C cold acclimation.%[目的]棉花苗期易受低温伤害,适宜的低温锻炼可以提高棉苗耐冷性.通过观察晋棉49、科能0518棉苗真叶细胞超微结构,分析12°C低温锻炼对4°C冷胁迫适应性的影响.[方法]将上述2个品种脱绒后的棉种浸泡适当时间,于28°C/12 h光照条件下培养至长出至少2片真叶后,均分为2组:一组作为对照(未低温锻炼),另一组于12°C/12 h光照条件下低温锻炼5d,然后2组均于4°C/12h光照条件下冷胁迫5d,在电镜下观察、比较、分析其真叶细胞超微结构的变化.[结果]经过12°C锻炼5d后在4°C冷胁迫过程中,相比未经锻炼处理,晋棉49叶绿体结构更完整,且积累淀粉粒,细胞之中出现高电子吸收物质;科能0518叶绿体结构也更完整,积累更多的淀粉粒,核膜完整,线粒体聚集排列、结构完整,内质网呈管状和泡状,细胞内同样出现大量高电子吸收物质.[结论]经过12°C低温锻炼,棉苗可以通过维持叶绿体的完整性,积累淀粉粒,在细胞质中积累高电子吸收物质来适应4°C冷胁迫.
