A prominent hypothesis for the adaptive value of anthocyanin production in the autumn leaves of trees and shrubs is that anthocyanins protect leaves from photooxidative stress at low temperatures, allowing a better resorption of nutrients-in particular, nitrogen-before leaf fall. While there is evidence that anthocyanins enable photoprotection, it is not clear whether this translates to improved nitrogen translocation and how this can explain inter-specific variation in autumn colours. A recent comparative analysis showed no correlation between temperature and anthocyanin production across species but did not analyse nitrogen content and nitrogen resorption efficiency. Here, we provide this comparison by analysing the nitrogen content of mature and senescent leaves and their autumn colours in 55 species of trees. We find no correlation between the presence of anthocyanins and the efficiency of nitrogen resorption. We find, instead, that nitrogen resorption is more efficient in species with yellow autumn colours, pointing to chlorophyll resorption, rather than anthocyanin synthesis, as the main determinant of nitrogen translocation efficiency. Hence, our results do not corroborate the photoprotection hypothesis for the evolution of autumn colours.

中文翻译：

---

对秋天颜色演变的光保护假设的测试：叶绿素吸收，而不是花青素的产生，与氮转运相关。

树木和灌木秋叶中花青素产生的适应性价值的一个突出假设是，花青素在低温下保护叶子免受光氧化应激，从而在落叶前更好地吸收养分，特别是氮。虽然有证据表明花青素具有光保护作用，但尚不清楚这是否会转化为改善的氮转运，以及这如何解释秋季颜色的种间差异。最近的一项比较分析表明，温度和物种间花青素产量之间没有相关性，但没有分析氮含量和氮再吸收效率。在这里，我们通过分析 55 种树木的成熟和衰老叶片的氮含量及其秋天的颜色来提供这种比较。我们发现花青素的存在与氮再吸收效率之间没有相关性。相反，我们发现氮再吸收在秋季黄色的物种中更有效，这表明叶绿素再吸收而不是花青素合成是氮转运效率的主要决定因素。因此，我们的结果并未证实秋季颜色演变的光保护假设。