Effects of experimental warming on Betula nana epidermal cell growth tested over its maximum climatological growth range.

Fabian E Z Ercan,Mariusz Lamentowicz,Juha Mikola,Tarja Silfver,Friederike Wagner-Cremer,Kristiina Myller,Sandra Słowińska,Elina Vainio,Daan Blok,Michał Słowiński

doi:10.1371/journal.pone.0251625

Abstract

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.

Highlights

A warmer environment affects plant growth and metabolism, causes shifts in phenology, and alters survival and reproductive success [1, 2]
For all localities we studied leaf samples collected from plots with ambient temperature and those collected from plots treated with either open top chambers (OTC) or ceramic heaters to induce warming (Table 1)
The B. nana epidermal cell undulation index (UI) was compared between the ambient, or control (C) temperature and warming (W) for each site (Fig 4)

Summary

Introduction

A warmer environment affects plant growth and metabolism, causes shifts in phenology, and alters survival and reproductive success [1, 2]. Such adjustments in vegetation are expected to be especially pronounced in northern high latitudes, where ongoing climate change leads to rapidly warming growth conditions [3]. In order to quantify and predict future vegetation dynamics, field experiments are performed in various sites across the globe Such in-situ experiments generate realistic settings, where environmental background conditions are maintained, while relevant abiotic growth parameters such as temperature are adjusted [4, 5]. The ontogenetic succession of leaf growth and maturation, is understudied the degree of leaf maturity is an important indication for response potential to such minor changes in growth conditions that might not be captured by using other traits [12]

Methods

Results

Conclusion