中国农业科学

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最新录用:低温胁迫对番茄幼苗不同叶龄叶片叶绿素荧光成像特性的影响

胡雪华1,刘宁宁1,陶慧敏1,彭可佳1,夏晓剑2,胡文海1
  

  1. 1井冈山大学生命科学学院江西吉安 333009;2浙江大学农业与生物技术学院园艺系,杭州 310058
  • 发布日期:2022-07-14

Effects of Chilling on Chlorophyll Fluorescence Imaging Characteristics of Leaves with Different Leaf Ages in Tomato Seedlings

HU XueHua1, LIU LingLing1, TAO HuiMin1, PENG KeJia1, XIA XiaoJian2, HU WenHai1 #br#   

  1. 1School of Life Sciences, Jinggangshan University, Ji’an, Jiangxi 343009; 2College of Agriculture and Biotechnology, Zhejiang University, Hangzhou, 310058
  • Online:2022-07-14

摘要: 【目的】研究番茄幼苗第2叶(成熟叶)和第4叶(新生叶)叶绿素荧光成像特性对低温胁迫的响应,并分析低温胁迫下番茄不同叶龄叶片光合活性区域相对面积及荧光参数值的变化,以探明番茄幼苗不同叶龄叶片对低温胁迫的适应机制。【方法】以番茄品种‘中蔬4号’(Solanum lycopersicum L. cv Zhongshu No.44叶期幼苗为材料,对番茄幼苗进行低温(8℃,200 μmol·m-2·s-1)处理15 d后常温(26℃白天/20℃夜晚,500 μmol·m-2·s-1)恢复1 d,于处理不同时期对幼苗全株进行叶绿素荧光成像,并比较第2叶和第4叶的叶绿素荧光成像特性。【结果】低温处理期间,第4叶的光合活性区域相对面积(RAP)仅在处理前期(5 d)有所下降,而全株和第2叶的RAP则随处理时间的延长持续下降,但常温恢复1 d即可完全恢复。低温处理下PSII调节性能量耗散的量子产量(Y(NPQ))PSII非调节性能量耗散的量子产量(Y(NO))和非光化学猝灭(NPQ)的荧光活性区域相对面积(RAF)与RAP基本一致,但PSII实际光化学效率(Y(II))和光化学猝灭(qP)的RAF则显著低于RAP。低温处理前期(5 d),番茄幼苗光合活性区域的PSII最大光化学效率(Fv/Fm)Y(NPQ)NPQ急剧下降和Y(NO)急剧上升,随后,Fv/Fm保持不变,但Y(NPQ)NPQ有所上升,Y(NO)则下降。但是,低温处理1 d即导致光合活性区域Y(II)的急剧下降,随后维持不变。令人感兴趣的是,番茄全株和第4叶的光合活性区域qP仅表现在处理第1 d时小幅下降,随后则维持高于处理前水平,而第2qP则在第5 d有明显上升后又迅速下降。总体上第4叶光合活性区域的Fv/FmY(II)Y(NPQ)NPQqP明显高于第2叶,Y(NO)低于第2叶。【结论】番茄幼苗可通过主动降低叶片光合活性区域面积来适应低温胁迫,而叶片热耗散能力在低温处理前期受到抑制,直到处理后期才逐渐发挥其光保护作用;低温胁迫下番茄幼苗优先保护生长点和新生叶,成熟叶主要通过可逆降低光合活性区域面积来适应低温胁迫,而新生叶则主要通过维持相对较高的PSII反应中心光化学和热耗散能力防御低温光抑制;低温导致新生叶光合活性区域中部分有活性的PSII反应中心关闭的同时,刺激了剩余有活性PSII反应中心开放程度的提高,这将有利于低温胁迫解除后恢复期光合活性的恢复。


关键词: 番茄, 低温胁迫, 叶绿素荧光成像, 光抑制, 叶龄

Abstract: ObjectiveThis study analyzed the characteristics of chlorophyll fluorescence imaging of the 2nd (mature) and 4th (newly born) leaves of tomato seedlings in response to chilling stress, aiming to probe the mechanism by which leaves with different ages adapted to chilling stress in tomato seedlings.【Method】In this study, Solanum lycopersicum L. cv Zhongshu No.4 was used as the research material. The tomato seedlings in the 4-leaf stage were treated at chilling (8℃, 200 μmol·m-2·s-1) for 15 d and then recovered at normal temperature (26℃ day/20℃ night, 500 μmol·m-2·s-1) for 1 d. Chlorophyll fluorescence imaging of the whole seedlings was measured at different stages of treatment, and the characteristics of chlorophyll fluorescence imaging of the 2nd and 4th leaves were compared. 【Result】The results showed that the relative area of photosynthetically active regions (RAP) on the 4th leaves decreased slowly during the first 5 d of the chilling stress, while the RAP on the 2nd leaves and the whole plants decreased steadily during the whole chilling treatment. The RAP recovered completely after 1 d of recovery. Under chilling treatment, the relative area of fluorescence active regions (RAF) for quantum yield of regulatory energy dissipation (Y(NPQ)), quantum yield of nonregulatory energy dissipation (Y(NO)), and nonphotochemical quenching (NPQ) showed similar changes as that of RAP. However, the RAF of effective PSII quantum yield (Y(II)) and coefficient of photochemical quenching (qP) were significantly lower than RAP. Maximum PSII quantum yield (Fv/Fm), Y(NPQ), and NPQ decreased while Y(NO) increased sharply in the photosynthetically active region in tomato seedlings during the first 5 d of the chilling treatment. In the following days, the Fv/Fm remained unchanged, whereas Y(NPQ) and NPQ increased and Y(NO) decreased. However, Y(II) declined sharply 1 d after chilling stress and then remained unchanged. Interestingly, qP in the photosynthetic active region of the 4th leaves decreased only slightly after 1 d of chilling treatment, and then maintained higher than that before treatment. However, qP of the 2nd leaves increased significantly on the 5th day and then decreased rapidly. Overall, the Fv/Fm, Y(II), Y(NPQ) and qP in the 4th leaves were higher than those in the 2nd leaves, whereas the Y(NO) were relatively lower in the 4th leaves.【Conclusion】The study found that tomato seedlings responded to chilling stress by decreasing the area of photosynthetically active regions. The regulatory nonphotochemical quenching, which plays a central role in photoprotection, was inhibited in the early stage, but gradually increased during the later stage of chilling treatment. Mature leaves adapted to chilling stress likely by decreasing the size of photosynthetically active regions, while higher capacities of PSII photochemistry and thermal dissipation were maintained in the newly born leaves in response to chilling stress. Protection of the shoot apex and the newly born leaves may be the priority of tomato seedlings in response to chilling stress. For newly born leaves, chilling induced the closure of some active PSII reaction centers, but improved the operating efficiency of the remaining active PSII reaction centers, which is potentially beneficial for the recovery of photosynthetic activity during the recovery period.


Key words: tomato (Solanum lycopersicum L.), chilling stress, chlorophyll fluorescence imaging, photoinhibition, leaf age