水分胁迫对三叶青叶绿体超微结构及黄酮合成关键酶的影响

  目的  探究水分胁迫对三叶青Tetrastigma hemsleyanum叶绿体超微结构及黄酮合成关键酶活性的影响，有利于提升三叶青的品质。  方法  以2年生三叶青实生苗为材料，通过控水盆栽试验(设置水涝、干旱和对照)，分析水分胁迫对三叶青叶绿体超微结构、块根总黄酮质量分数以及黄酮合成途径中的3个关键酶[苯丙氨酸解氨酶(PAL)、查尔酮合成酶(CHS)和查尔酮异构酶(CHI)]活性的影响。  结果  干旱和水涝均引起三叶青叶片叶绿体数量减少，叶绿体质体小球的数量增多、体积变大、颜色变浅，叶绿体基粒片层结构不再整齐紧密；干旱时，三叶青总黄酮质量分数在胁迫12 d达到峰值，水涝时则在胁迫16 d达到峰值，而PAL、CHS和CHI等3个关键酶则在黄酮质量分数达到峰值前期或者是同期表现出较高的活性；随着胁迫时间的延长，黄酮质量分数和关键酶活性都有不同程度的下降，黄酮质量分数与PAL、CHS、CHI活性均显著相关(P＜0.05)。  结论  适度的水分胁迫可提高三叶青块根中黄酮类化合物的质量分数以及相关酶的活性。图7表1参36

Effects of water stress on chloroplast ultrastructure and key enzymes of flavonoid synthesis in Tetrastigma hemsleyanum

  Objective  This study aims to investigate the effects of water stress on the ultrastructure of chloroplast and the activity and content of key enzymes in the flavonoid synthesis pathway of Tetrastigma hemsleyanum, so as to improve the quality of T. hemsleyanum.  Method  With two-year-old seedlings of T. hemsleyanum as materials, and through water control pot experiments (setting waterlogging, drought, and the control), the effects of water stress on chloroplast ultrastructure, root flavonoid content and the activities of three key enzymes [phenylalanine ammonia lyase(PAL), chalcone synthase(CHS) and chalcone isomerase(CHI)] in flavonoid synthesis pathway were analyzed.  Result  Drought and waterlogging both caused the decrease of chloroplast number in the leaves, and they moved toward the center of the cell instead of clinging to the cell wall. Besides, the number of plastid globules in the chloroplast increased and the volume became larger, the color became lighter, and the lamella structure of chloroplast was no longer neat and compact. The total flavonoid content of T. hemsleyanum reached the peak on the 12th day under drought stress, and reached the peak on the 16th day under waterlogging stress. Analysis of key enzyme activities in the biosynthetic pathway of flavonoids showed that the activities of PAL, CHS and CHI increased successively in the early stage of the maximum flavonoid content or during the same period, but with the extension of stress time, the total flavonoid content and key enzyme activities decreased in varying degrees. There was a significant correlation between the content of flavonoids and the activities of PAL, CHS, and CHI (P＜0.05).  Conclusion  Moderate water stress can increase the content of flavonoids in the roots of T. hemsleyanum and enhance the activity of related enzymes. [Ch, 7 fig. 1 tab. 36 ref.]