2025-04-23 京都大学
京都大学の研究グループは、落葉広葉樹33種の葉の力学・化学特性を比較し、「ケイ素濃度が高い葉は硬いが脆い」とする仮説を検証した。ガラス成分であるケイ素は炭素の代用として細胞壁を強化するが、同時に葉の脆さを高める可能性があることが示された。これは、植物がケイ素を取り込むか否かの進化的選択に影響する要因を解明する手がかりとなり、植物の多様なケイ素利用戦略の理解に貢献する。
<関連情報>
- https://www.kyoto-u.ac.jp/ja/research-news/2025-04-23-0
- https://www.kyoto-u.ac.jp/sites/default/files/2025-04/web_2504_Onoda-1621b81238a8455fbc8020fa318882ac.pdf
- https://nph.onlinelibrary.wiley.com/doi/10.1111/nph.70079
広葉樹の落葉樹33種において、ケイ素は葉の薄板の剛性を高めるが引張強度は高めないが、セルロースはその両方を高める Across 33 broad-leaved deciduous woody species, silicon enhances leaf lamina stiffness but not tensile strength whereas cellulose enhances both
Hirofumi Kajino, Yusuke Onoda, Kaoru Kitajima
New Phytologist Published: 10 April 2025
DOI:https://doi.org/10.1111/nph.70079
Summary
- Silicon (Si) has been hypothesized to be a metabolically cheaper substitute for carbon-based cell wall components to support leaves. However, how the biomechanical function of Si, deposited as amorphous silica, differs from cell wall components remains untested. Here, we tested the hypothesis that species with higher leaf Si concentrations have stiffer but more brittle leaf lamina.
- We measured the mechanical properties, including modulus of elasticity (E), tensile strength (σmax), and maximum strain (εmax), tissue density, and the concentrations of Si and cell wall components for 33 deciduous broad-leaved woody species.
- Multiple regression results showed that tissue density, Si concentration, and cellulose concentration contributed positively to E and negatively to εmax. By contrast, tissue density and cellulose concentration, but not Si concentration, contributed to σmax. No significant contribution of lignin concentration to mechanical properties was detected.
- These results suggest that Si might function as a substitute for cellulose to increase stiffness but not the strength of a lamina. Greater Si concentration decreased εmax without increasing σmax, which made the lamina more brittle. The brittleness associated with Si might explain a potential cost or disadvantage of using Si, which would elucidate the trade-offs between species with different leaf Si concentrations.
