Shiono Katsuhiro, Koshide Akiko, Iwasaki Kazunari, Oguri Kazumasa, Fukao Takeshi, Larsen Morten, Glud Ronnie N
Department of Bioscience and Biotechnology, Fukui Prefectural University, Fukui, Japan.
HADAL and Nordcee, Department of Biology, University of Southern Denmark, Odense, Denmark.
Front Plant Sci. 2022 Jul 29;13:946776. doi: 10.3389/fpls.2022.946776. eCollection 2022.
Submergence during germination impedes aerobic metabolisms and limits the growth of most higher plants. However, some wetland plants including rice can germinate under submerged conditions. It has long been hypothesized that the first elongating shoot tissue, the coleoptile, acts as a snorkel to acquire atmospheric oxygen (O) to initiate the first leaf elongation and seminal root emergence. Here, we obtained direct evidence for this hypothesis by visualizing the spatiotemporal O dynamics during submerged germination in rice using a planar O optode system. In parallel with the O imaging, we tracked the anatomical development of shoot and root tissues in real-time using an automated flatbed scanner. Three hours after the coleoptile tip reached the water surface, O levels around the embryo transiently increased. At this time, the activity of alcohol dehydrogenase (ADH), an enzyme critical for anaerobic metabolism, was significantly reduced, and the coleorhiza covering the seminal roots in the embryo was broken. Approximately 10 h after the transient burst in O, seminal roots emerged. A transient O burst around the embryo was shown to be essential for seminal root emergence during submerged rice germination. The parallel application of a planar O optode system and automated scanning system can be a powerful tool for examining how environmental conditions affect germination in rice and other plants.
发芽期间的淹水会阻碍有氧代谢，并限制大多数高等植物的生长。然而，包括水稻在内的一些湿地植物能够在淹水条件下发芽。长期以来，人们一直推测，第一个伸长的茎组织——胚芽鞘，起着通气管的作用，获取大气中的氧气（O）以启动第一片叶子的伸长和种子根的长出。在这里，我们通过使用平面氧传感器系统可视化水稻淹水发芽过程中的时空氧动态，为这一假设获得了直接证据。在进行氧成像的同时，我们使用自动平板扫描仪实时跟踪茎和根组织的解剖发育。胚芽鞘尖端到达水面三小时后，胚周围的氧水平短暂升高。此时，对无氧代谢至关重要的乙醇脱氢酶（ADH）的活性显著降低，覆盖胚中种子根的胚根鞘破裂。在氧短暂激增大约10小时后，种子根长出。胚周围的短暂氧激增被证明是水稻淹水发芽过程中种子根长出所必需的。平面氧传感器系统和自动扫描系统的并行应用可以成为研究环境条件如何影响水稻和其他植物发芽的有力工具。
