Analysis of threshold of breeding resources necessary for fruit induction of subtropical evergreen broad-leaved trees

2022 Fiscal Year Final Research Report

• Project/Area Number: 17K07846
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Forest science
• Research Institution: University of the Ryukyus
• Principal Investigator: Taniguchi Shingo 琉球大学, 農学部, 教授 (80444909)
• Project Period (FY): 2017-04-01 – 2023-03-31
• Keywords: 樹木繁殖 / 開花結実 / 豊凶周期（マスティング） / 13C安定同位体 / 繁殖資源 / 非構造性炭水化物 / リュウキュウコクタン / 亜熱帯島嶼

Outline of Final Research Achievements

We attempted to elucidate the pattern of transport of photosynthetic products of reproductive resources obtained in photosynthetic organs (sources) of leaves to reproductive organs (sinks) of flowers and fruits by 13C stable isotope tracer method (from which source to which sink at each reproductive stage) and its mechanism in manipulation experiments. As a result, it was found that "the photosynthate of the current year of fruiting" was mainly consumed in a good harvest year, while "carbohydrates stored in the branches in the previous year of fruiting were first consumed and then the photosynthate of the current year was consumed" in a normal or bad harvest year. However, the experimental hypothesis that a poor crop in the year following a good crop year was caused by a carbon and nitrogen deficiency in the tree body due to sinking too much carbon and nitrogen in the good crop year, which inhibited flower bud differentiation in the following year, was not clearly understood.

Free Research Field

森林科学

Academic Significance and Societal Importance of the Research Achievements

亜熱帯常緑広葉樹の光合成産物（炭水化物）を安定同位体の標識法を用いて生理的な観点から繁殖資源の配分特性を把握した本研究の成果は、果実の豊凶現象の発生に対する至近要因ならびに究極要因の新たな解釈と豊凶現象の発生メカニズムの解明につながる基礎知見となることが期待される。本研究は13C安定同位体の標識法により繁殖ステージごとに繁殖資源の供給源と配分先を判明することができた。これらの結果をもとに、結実の豊凶現象の発生メカニズムと周期性に関する議論をさらに発展させることになり、学術的な意義は高い。しかし、炭素と窒素を多量に集積した翌年に樹体内の炭素・窒素不足が花芽分化を阻害する現象の解明はできなかった。