849 ISSN 1021-4437, Russian Journal of Plant Physiology, 2016, Vol. 63, No. 6, pp. 849–860. © Pleiades Publishing, Ltd., 2016. Original Russian Text © L.A. Ivanova, A.G. Chanchikova, D.A. Ronzhina, N.V. Zolotareva, V.V. Kosulnikov, R.M. Kadushnikov, L.A. Ivanov, 2016, published in Fiziologiya Rastenii, 2016, Vol. 63, No. 6, pp. 860–872. Leaf Acclimation to Experimental Climate Warming in Meadow Plants of Different Functional Types L. A. Ivanova a, *, A. G. Chanchikova c , D. A. Ronzhina a , N. V. Zolotareva b , V. V. Kosulnikov c , R. M. Kadushnikov c , and L. A. Ivanov a a Botanical Garden, Ural Branch, Russian Academy of Sciences, ul. 8 Marta 202a Yekaterinburg, 620144 Russia b Institute of Ecology of Plants and Animals, Ural Branch, Russian Academy of Sciences, Yekaterinburg, 620144 Russia c Yeltsin Ural Federal University, Yekaterinburg, 620002 Russia *e-mail: Larissa.Ivanova@botgard.uran.ru Received November 13, 2015 Abstract—The use of open-top chambers (OTCs) installed in natural plant cover is one of the approaches to study plant responses to climate change. Three OTCs made from polyethylene film were installed on a herb- grass meadow in the subzone of the southern taiga before the beginning of the growing season. A significant increase in the average daily temperature values (by 0.5°C) and the relative humidity (by 10%) compared to control conditions was observed inside the chambers. Plant height, leaf parameters, and the pigments content were studied for six species of meadow plants during the growing season in two variants—inside the chamber and outside the chamber (control); more than 20 quantitative parameters of the mesophyll were studied for four of the species. It was found that the differences in microclimatic conditions had no effect on plant height and leaf area. A slight decrease in the thickness and density of the leaves and an increased water content were noted inside the OTCs. In contrast to weak changes in external leaf parameters, the internal leaf structure and the content of photosynthetic pigments varied considerably. Warming caused the reduction of the content of chlorophyll and carotenoids per unit leaf area in the majority of studied species, except for Veronica cha- maedrys L., but the ratio of pigment forms did not change. Changes in the pigments content in the leaf were associated with some structural rearrangements in the mesophyll, whose mechanism depended on the func- tional properties of the species. Increased size of palisade cells and the number of chloroplasts per cell was noted in the ruderal species (R/CSR-strategist) Taraxacum officinale Wigg. s. l.; the reduction of chlorophyll content per leaf area occurred due to the decrease in chlorophyll content per a single chloroplast. Decreased number of cells and chloroplasts per leaf unit area without any changes in their size was marked for the species with S/CSR strategy Alchemilla vulgaris L. s. 1. and V. chamaedrys L. in a chamber, but the content of chlo- rophyll per a chloroplast increased. An increase in the number of cells and a simultaneous decrease in their size was observed in CR-strategist Cirsium setosum (Willd.) Bess. inside the OTC; the chlorophyll content per chloroplast did not change. It was concluded that the acclimation of plants to short-term climate warming was associated with the restructuring of leaf mesophyll, whose mechanism depended on the functional prop- erties of the species. Keywords: leaf traits, mesophyll structure, chlorophyll, carotenoids, climate change, open top chamber, plant functional types DOI: 10.1134/S102144371605006X INTRODUCTION Global climate change observed in recent decades is associated with a progressive increase in the tem- perature and the concentration of “greenhouse” gases in the atmosphere [1]. Continuous emission of green- house gases, caused by human activities, also contrib- utes to climate change [1, 2]. “Greenhouse effect” should cause the adaptive changes in the structural and functional organization of plants, the direction and extent of which may vary in different species. Some species may be more sensitive to climate warm- ing than the others [2–4]. Species reaction may depend on its functional properties, such as the type of ecological strategy. Stress-tolerants (S-strategists) have a high capacity for physiological acclimation under changing climate conditions, while the compet- itors (C-strategists) respond to changed conditions by rapid changes in the morphology and growth; ruderals (R-strategists) respond by reduced growth and increased reproductive function [5]. Climate change Abbreviations: A mes /A—mesophyll cell surface area per leaf area, A chl /A—chloroplast surface area per leaf area, OTC—the open top chamber, LMA—leaf mass area, df—the number of degrees of freedom, F—Fisher’s test, p—probability, R 2 —determination coefficient. RESEARCH PAPERS