Dendrophysiological study on tree-ring oxygen and hydrogen isotopes using pulse-labeling with heavy water

2021 Fiscal Year Final Research Report

• Project/Area Number: 19K06179
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 40020:Wood science-related
• Research Institution: Forest Research and Management Organization
• Principal Investigator: Kagawa Akira 国立研究開発法人森林研究・整備機構, 森林総合研究所, 主任研究員 等 (40353635)
• Co-Investigator(Kenkyū-buntansha): 内海 泰弘 九州大学, 農学研究院, 准教授 (50346839)
• Project Period (FY): 2019-04-01 – 2022-03-31
• Keywords: 同位体 / パルスラベリング / 葉面水分吸収 / 重水 / 酸素 / 水素 / 光合成

Outline of Final Research Achievements

In biology textbooks, conventional photosynthetic illustrations mention only root uptake water, and it has been assumed that oxygen and hydrogen in cellulose originates from this water. However, recent studies show that plants also absorbs liquid water from leaves, and this is called "foliar water uptake". In our study, I pulse-labelled Japanese cedar saplings with heavy water during rainy season, when active earlywood formation happens. Therefore, radial growths during rainy seasons account for a significant contributions to tree-ring oxygen and hydrogen isotope ratios. I studied how foliar-absorbed water is then incorporated into the biomass of needles, roots and branches in the form of oxygen and hydrogen in cellulose etc. The results suggested that not only root-absorbed water, but also significant percentage of foliar-absorbed water is incorporated into biomass, in the form of oxygen and hydrogen in cellulose etc.

Free Research Field

同位体年輪気候学、樹木生理学、木材解剖学

Academic Significance and Societal Importance of the Research Achievements

本研究により、根から吸収した水だけではなく、葉から吸収した水も植物バイオマスの形成に用いられているという知見が得られた。この知見は、例えば苗木や農作物の栽培において潅水方法を最適化することにより（または水分と肥料を混ぜて与える葉面施肥方法を最適化することにより）、植物の成長量を最大化することに役立つ可能性がある。