Palaeoecology, Department of Physical Geography, Utrecht University, Utrecht, The Netherlands.
Kevo Subarctic Research Institute, Biodiversity Unit of the University of Turku, Utsjoki, Finland.
PLoS One. 2021 May 19;16(5):e0251625. doi: 10.1371/journal.pone.0251625. eCollection 2021.
Numerous long-term, free-air plant growth facilities currently explore vegetation responses to the ongoing climate change in northern latitudes. Open top chamber (OTC) experiments as well as the experimental set-ups with active warming focus on many facets of plant growth and performance, but information on morphological alterations of plant cells is still scarce. Here we compare the effects of in-situ warming on leaf epidermal cell expansion in dwarf birch, Betula nana in Finland, Greenland, and Poland. The localities of the three in-situ warming experiments represent contrasting regions of B. nana distribution, with the sites in Finland and Greenland representing the current main distribution in low and high Arctic, respectively, and the continental site in Poland as a B. nana relict Holocene microrefugium. We quantified the epidermal cell lateral expansion by microscopic analysis of B. nana leaf cuticles. The leaves were produced in paired experimental treatment plots with either artificial warming or ambient temperature. At all localities, the leaves were collected in two years at the end of the growing season to facilitate between-site and within-site comparison. The measured parameters included the epidermal cell area and circumference, and using these, the degree of cell wall undulation was calculated as an Undulation Index (UI). We found enhanced leaf epidermal cell expansion under experimental warming, except for the extremely low temperature Greenland site where no significant difference occurred between the treatments. These results demonstrate a strong response of leaf growth at individual cell level to growing season temperature, but also suggest that in harsh conditions other environmental factors may limit this response. Our results provide evidence of the relevance of climate warming for plant leaf maturation and underpin the importance of studies covering large geographical scales.
目前，许多长期、自由大气植物生长设施正在探索北方地区植被对持续气候变化的响应。开顶式气室（OTC）实验以及主动增温的实验装置侧重于植物生长和性能的许多方面，但有关植物细胞形态变化的信息仍然很少。在这里，我们比较了原位增温对芬兰、格陵兰和波兰矮桦（Betula nana）叶片表皮细胞扩张的影响。这三个原位增温实验的地点代表了 B. nana 分布的对比区域，芬兰和格陵兰的地点分别代表了低和高北极的当前主要分布区，而波兰的大陆地点则是 B. nana 全新世微避难所的遗留地。我们通过对 B. nana 叶片角质层的微观分析来量化表皮细胞的侧向扩张。这些叶子是在具有人工增温和环境温度的配对实验处理地块中产生的。在所有地点，在生长季结束时收集两年的叶子，以促进地点之间和地点内部的比较。测量的参数包括表皮细胞的面积和周长，并使用这些参数计算细胞壁波动的程度作为波动指数（UI）。我们发现实验增温下叶片表皮细胞扩张增强，除了温度极低的格陵兰地点外，处理之间没有显著差异。这些结果表明，在个体细胞水平上，叶片生长对生长季温度有强烈的响应，但也表明在恶劣条件下，其他环境因素可能会限制这种响应。我们的结果提供了气候变暖对植物叶片成熟的重要性的证据，并强调了涵盖大地理尺度研究的重要性。
