杂交鹅掌楸体胚再生植株淹水胁迫下叶片超微结构及光合特性变化

摘要

[目的]研究不同淹水胁迫处理时间下杂交鹅掌楸植株表型、叶绿体超微结构及光合特性的响应变化,揭示杂交鹅掌楸在淹水胁迫下的响应机制,为其栽培管理和多涝害地区的应用推广提供理论依据.[方法]以无菌培养条件下3～5个叶片的杂交鹅掌楸体胚再生植株为研究对象,采用无菌水完全淹没植株的方法模拟水淹灾害,以正常培养条件为对照,研究不同淹水胁迫处理时间(1、3、5、7和7天后恢复处理2天)下杂交鹅掌楸植株表型、光合特性的响应变化以及对叶绿体超微结构的影响.[结果]1)在不同时间的淹水胁迫处理中,杂交鹅掌楸体胚植株受涝害的程度随着淹水时间的延长而明显加重;植株叶片从基部开始卷曲、黄化甚至脱落,但顶芽无明显变化,这可能是杂交鹅掌楸在淹水胁迫中启动相应保护机制以应对淹水胁迫环境.2)淹水胁迫处理过程中叶绿体肿胀变形,膜系统严重损伤,甚至降解,基粒和基质片层堆叠紊乱,淀粉粒不断积累,嗜锇颗粒电子密度增大,胁迫后期出现聚集现象,说明淹水胁迫导致杂交鹅掌楸叶绿体超微结构严重破坏.3)淹水胁迫处理过程中净光合速率、气孔导度和蒸腾速率呈明显下降趋势,而细胞间CO2浓度呈缓慢上升趋势;光系统Ⅱ的光合电子传递速率、光化学淬灭系数、最大光化学效率和光化学实际量子产量均呈现显著下降趋势,淹水7天并恢复处理2天后光合作用特性参数出现一定程度的恢复,这表明淹水胁迫使杂交鹅掌楸关闭了与外界进行气体交换的气孔通道,并对光系统Ⅱ活性中心造成严重损伤.[结论]长时间淹水胁迫可引起杂交鹅掌楸叶绿体超微结构的破坏,进而损伤光系统Ⅱ反应中心,进而光能转换效率降低,造成叶片光合作用能力降低,最终严重影响植株生长发育.因此,在杂交鹅掌楸的栽培管理中土壤水分含量不宜长期过高.%[Objective] In this study,we investigated the changes of the phenotype,chloroplast ultrastructure and photosynthetic characteristics of Liriodendron sino-americanum under waterlogging stress,to reveal the response mechanism of L.sino-americanum in waterlogged stress and thereby provide a theoretical basis for promotion of cultivation and application in waterlogged districts.[Method] L.sino-americanum somatic embryo regeneration seedlings with 3-5 leaves were subjected to sterile waterlogging treatment for various durations (1d,3d,5d,7d,and 2d recovery after 7days waterlogging),and the effects of the treatments on phenotype,chloroplast ultrastructure and photosynthetic characteristics were investigated.[Result] The results indicated that:1) The longer waterlogging treatment led to more severe damages to L.sino-americanum seedlings including curled and yellow leaves,or even leaves fell off from the base.However,the apical buds had no obvious changes,which could be due to the defense mechanism initiated by L.sino-americanum under waterlogging stress.2) Waterlogging stress resulted in swelled chloroplasts and severe damages to the chloroplast ultrastructure of L.sino-americanum including degradation of chloroplast membrane system,loose and disordered arrangement of grana and stoma lamella,accumulation of starch grains,and osmiophilic granules density increased and and gathered together at the late stage of stress.3) The net photosynthetic rate,stomatal conductance and transpiration rate were decreased whereas intercellular CO2 concentration was increased slowly.The electron transport rate,photochemical quenching coefficient,photochemical efficiency and photochemical actual quantum yield in photosynthesizerⅡ showed a significant decline.The photosynthetic characteristics were partially restored after 2 days recovery treatment after 7d waterlogging stress.These data suggested that waterlogging stress caused serious damage in photosynthesizer Ⅱ activity center,and L.sino-americanum reduced gas exchanges by closing the stomata.[Conclusion] Taken together,waterlogging stress can cause the damages of chloroplast ultrastructure of L.sino-americanum,and then damage the photosynthesizer Ⅱ activity center,resulting in a decrease in leaf photosynthetic capacity and inhibition on growth and development of L.sinoamericanum seedlings,but the seedlings may obtain to certain degree resistance under short-term waterlogging stress.