This study intended to clarify whether low irradiance, high temperature or both acted as a trigger inducing summer dormancy in Daphne pseudomezereum (Dpm), a wintergreen shrub native to Japanese mixed forests. A 2-year growth chamber experiment was conducted in Otsu, Japan where, in the first year, 3 provenances of Dpm were raised in two irradiance levels by two temperature regimes to observe their effects on leaf phenology. The results showed a clear effect of temperature, but not irradiance, on leaf phenology. In the second year, the experiment was repeated using different Dpm plants and applying only the two temperature regimes. The results confirmed those obtained in the first year, where the temperature regime that tracked normal field condition induced summer dormancy similar to field populations. In both years, when plants were kept over the summer under a cool temperature regime mimicking field conditions in April, most plants did not undergo summer dormancy (i.e., becoming “evergreen”). In contrast to phenology, leaf morphology (i.e., LMA), and photosynthetic capacity (e.g., A_max) did respond to irradiance levels consistent with shade adaptive changes, but were not affected by temperature. Simulated carbon gain using previously determined parameters for Dpm and the chamber microclimate data found that only plants in the warm treatment experienced carbon deficit in mid-summer. These findings suggest that summer temperature alone and the attendant rise in respiration can alter internal carbon balance and trigger the onset of summer dormancy in Dpm.

这项研究旨在阐明低辐照度，高温或两者均是引起达芙妮假mezereum夏季休眠的诱因（Dpm），一种日本混合森林原生的冬绿色灌木。在日本大津市进行了为期2年的生长室实验，在第一年中，在两种辐照水平下，通过两种温度制度，提高了3种Dpm的Dpm种源，以观察其对叶片物候的影响。结果表明温度对叶片物候有明显的影响，但辐照度没有。在第二年，使用不同的Dpm工厂并仅应用两种温度方案重复了该实验。结果证实了第一年获得的结果，在该温度下，追踪正常田间条件的温度机制导致夏季休眠类似于田间种群。在这两个年度中，当植物在模拟夏季气候的酷暑条件下于4月在夏季保存时，大多数植物都没有经历夏季休眠（即，变得“常绿”）。与物候相反，叶片形态（即LMA）和光合能力（例如，一个_最大值）没有到辐射水平与遮阳的适应性变化一致的回应，但并没有受到温度的影响。使用先前确定的Dpm参数和室内微气候数据模拟的碳增加量发现，只有处于温暖处理的植物在仲夏才出现碳缺乏。这些发现表明，仅夏季温度和随之而来的呼吸上升会改变内部碳平衡并触发Dpm夏季休眠的开始。