Ono Kiyomi, Hashiguchi Megumi, Tanaka Ryouichi, Hara Toshihiko
Institute of Low Temperature Science, Hokkaido University, Sapporo, Hokkaido, Japan.
J Plant Res. 2025 Mar;138(2):215-230. doi: 10.1007/s10265-024-01607-3. Epub 2024 Dec 17.
Sasa senanensis (a dwarf bamboo), an evergreen herbaceous plant native to the cool temperate regions of eastern Asia, endures seasonal temperature fluctuations and significant variations in light intensity typical for understory plants. Following snowmelt in early spring, the light intensity received by Sasa leaves surges, then diminishes as the canopy of upper deciduous trees develops. The current-year leaves of S. senanensis unfold under these shaded conditions, rendering the preservation of overwintering leaves vital for maintaining photosynthetic productivity in early spring. This study investigated the adaptations of overwintering leaves of S. senanensis to the low temperatures and elevated light conditions typical of early spring, examining whether these leaves dissipate absorbed light energy as heat and/or reduce their antenna size in response to increased light levels. Comprehensive analyses of Fv/Fm and photosynthetic pigment compositions were conducted throughout the spring to autumn seasons from 2014 to 2017. Our results indicate that Fv/Fm in overwintering leaves was initially low in early spring but increased gradually before the onset of shading, maintaining high levels under shaded conditions across all examined years. The chlorophyll a/b ratio increased post-snowmelt and decreased with intensified shading annually, with the exception of 2015, suggesting that reductions in antenna size are not essential for Fv/Fm recovery. Furthermore, the quantities and de-epoxidation state of xanthophyll cycle pigments increased after snowmelt despite rising temperatures, then decreased with progressive shading each year, indicating that overwintering leaves adapt to early spring conditions by modulating their xanthophyll cycle pigments. This study demonstrates that the overwintering leaves of S. senanensis exhibit a flexible response in photosystem pigments to variations in the light environment.
青篱竹（一种矮竹）是一种原产于东亚凉爽温带地区的常绿草本植物，能耐受季节性温度波动以及林下植物所特有的光照强度显著变化。早春融雪后，青篱竹叶接收到的光照强度激增，随后随着上层落叶乔木树冠的形成而减弱。当年生的青篱竹叶在这些遮荫条件下展开，因此越冬叶的保存对于维持早春的光合生产力至关重要。本研究调查了青篱竹越冬叶对早春典型的低温和高光条件的适应性，研究这些叶片是否会将吸收的光能以热量形式耗散和/或响应光照水平增加而减小其天线尺寸。在2014年至2017年的整个春至秋季节对Fv/Fm和光合色素组成进行了综合分析。我们的结果表明，越冬叶中的Fv/Fm在早春最初较低，但在遮荫开始前逐渐增加，在所有研究年份的遮荫条件下均保持较高水平。叶绿素a/b比值在融雪后增加，并且除2015年外每年随着遮荫加剧而降低，这表明天线尺寸的减小对于Fv/Fm恢复并非必不可少。此外，尽管温度升高，但叶黄素循环色素的含量和脱环氧化状态在融雪后增加，然后每年随着遮荫加剧而降低，这表明越冬叶通过调节其叶黄素循环色素来适应早春条件。本研究表明，青篱竹的越冬叶在光系统色素方面对光环境变化表现出灵活的响应。
