Heat stress is known to induce photoinhibition, leaf senescence, and nutrient remobilization in terrestrial plants with apical growth, however, its effect on blade erosion and associated-changes in chemical compositions has rarely been studied in marine macroalgae with intercalary growth such as kelp. The present study examined the combined effects of ocean warming (23 and 26°C), irradiance (30 and 180 μmol m–2 s–1), and nutrient enrichment (enriched and non-enriched) on photosystem II maximum efficiency (Fv/Fm) in the kelp Eisenia bicyclis. It also investigated the effect of ocean warming on the kelp’s relative growth rates based on five morphological parameters and three chemical compositions (carbon, nitrogen, and phlorotannnins). A warming effect on photoinhibition (i.e., decline in Fv/Fm) was only detected under the higher irradiance combined with nutrient-enrichment condition. Under this condition, elevated temperature decreased relative growth rates to negative values, indicating occurrence of apical blade erosion. Temperature elevation also caused increases in nitrogen and phlorotannin contents within the whole body, but not carbon content. Moreover, nitrogen content in the meristems at 26°C was higher than that at 23°C, although such a difference was not observed with phlorotannin content. These results suggested that heat-induced apical blade erosion promoted nitrogen accumulation in the meristems, located in the lower part of the blade, in E. bicyclis.

中文翻译：

---

热应激通过层间生长的棕色巨藻中的顶端叶片侵蚀促进分生组织中的氮积累

众所周知，热应激会在具有顶端生长的陆生植物中诱导光抑制、叶片衰老和养分再动员，但是，很少在海带等层间生长的海洋大型藻类中研究其对叶片侵蚀和相关化学成分变化的影响。本研究考察了海洋变暖（23 和 26°C）、辐照度（30 和 180 μmol m–2 s–1）和营养物富集（富集和非富集）对光系统 II 最大效率（Fv/ Fm) 在海带 Eisenia bicyclis 中。它还根据五种形态参数和三种化学成分（碳、氮和根皮单宁）研究了海洋变暖对海带相对生长率的影响。对光抑制的升温效应（即，Fv/Fm 的下降仅在较高的辐照度与营养丰富的条件下检测到。在这种情况下，升高的温度将相对增长率降低到负值，表明发生了顶端叶片侵蚀。温度升高也导致全身氮和根皮单宁含量增加，但碳含量不增加。此外，26°C 时分生组织中的氮含量高于 23°C 时的氮含量，尽管根皮单宁含量没有观察到这种差异。这些结果表明，热诱导的顶端叶片侵蚀促进了 E. bicyclis 叶片下部分生组织中氮的积累。表明发生顶端叶片侵蚀。温度升高也导致全身氮和根皮单宁含量增加，但碳含量不增加。此外，26°C 时分生组织中的氮含量高于 23°C 时的氮含量，尽管根皮单宁含量没有观察到这种差异。这些结果表明，热诱导的顶端叶片侵蚀促进了 E. bicyclis 叶片下部分生组织中氮的积累。表明发生顶端叶片侵蚀。温度升高也导致全身氮和根皮单宁含量增加，但碳含量不增加。此外，26°C 时分生组织中的氮含量高于 23°C 时的氮含量，尽管根皮单宁含量没有观察到这种差异。这些结果表明，热诱导的顶端叶片侵蚀促进了 E. bicyclis 叶片下部分生组织中氮的积累。