Nonstructural carbohydrate-balance response to long-term elevated CO₂ exposure in European beech and Norway spruce mixed cultures: biochemical and ultrastructural responses

Abstract

Two dominant central European tree species (Fagus sylvatica L. and Picea abies (L.) Karst.), in a mixed culture in semi-open glass domes, were used to simulate the reaction of forests to long-term elevated CO2 (EC) in a mountainous area (Beskydy Mountains, the Czech Republic). We investigated the effects of EC on soluble carbohydrate levels and composition. Starch content was evaluated using two methods: biochemical (glucose content after enzymatic hydrolysis) and stereological (starch grain proportion, size, and number in chloroplasts). In beech and spruce foliage, no significant changes in total soluble carbohydrate levels were observed. In spruce, starch content determined biochemically increased under EC, whereas no changes were detected in beech. The starch content determined stereologically increased only in beech. In spruce, EC exposure caused comparable starch increases in current-year and previous-year needles, although the former had a higher starch content and numerous larger starch grains regardless of CO2 concentration. In both species, the biochemical determination of carbohydrates exhibited greater individual tree uniformity, in contrast to large intraspecies variability. No changes in leaf soluble carbohydrates under long-term elevated CO2 demonstrate the ability of the studied tree species to efficiently allocate the photosynthates among the sinks. Thus, no photosynthetic downregulation via carbohydrate-level signalling can be expected.

Unbiased Estimation of Norway Spruce (Picea Abies L. Karst.) Chloroplast Structure: Heterogeneity Within Needle Mesophyll Under Different Irradiance and [Co2]

“…In the case of starch grain characteristics, this bias could mask CO 2 concentration impact if only TEM analysis is used. If the possibility of using SUR for chloroplast Image Anal Stereol 2019;38:83-94 evaluation is impeded by the extreme laboriousness or technical constraints, we recommend to combine TEM analysis with other physiological approaches, e.g., starch biochemical assessment (Mašková et al, 2017) or determination of photosystem activities and fluorescence parameters.…”

“…For chloroplast ultrastructural studies in broad leaves, the first or upper layers of leaf photosynthetic tissue, mesophyll, ( Fig. 1A) are often analysed (Günthardt-Goerg et al, 2000;Wheeler and Fagerberg 2000;Valkama et al, 2003;Velikova et al, 2009;Sun et al, 2011;Mašková et al, 2017). The first layer of mesophyll receives more incident irradiance than its deeper layers and thus, it can be regarded as the most important layer for photosynthesis.…”

Stereology, an Unbiased Methodological Approach to Study Plant Anatomy and Cytology: Past, Present and Future

“…Volume densities of thylakoids, starch, plastoglobuli and stroma inside chloroplasts were estimated by measuring the corresponding areas using the pointcounting method (Kutík et al, 1995;Miroslavov et al, 1996;Fagerberg and Bornman, 1997;Razem and Davis, 1999;Vassilyev, 2000;Wheeler and Fagerberg, 2000;Griffin et al, 2001;Gabarayeva and Grigorjeva, 2002;Pechová et al, 2003;Vičánková and Kutík, 2005;Gregoriou et al, 2007;Kubínová and Kutík, 2007;Holá et al, 2008, Mašková et al 2017.…”