Intra-annual dynamics of non-structural carbohydrates in the cambium of mature conifer trees reflects radial growth demands

Abstract

The presence of soluble carbohydrates in the cambial zone, either from sugars recently produced during photosynthesis or from starch remobilized from storage organs, is necessary for radial tree growth. However, considerable uncertainties on carbohydrate dynamics and the consequences on tree productivity exist. This study aims to better understand the variation in different carbon pools at intra-annual resolution by quantifying how cambial zone sugar and starch concentrations fluctuate over the season and in relation to cambial phenology. A comparison between two physiologically different species growing at the same site, i.e., the evergreen Picea abies Karst. and the deciduous Larix decidua Mill., and between L. decidua from two contrasting elevations, is presented to identify mechanisms of growth limitation. Results indicate that the annual cycle of sugar concentration within the cambial zone is coupled to the process of wood formation. The highest sugar concentration is observed when the number of cells in secondary wall formation and lignification stages is at a maximum, subsequent to most radial growth. Starch disappears in winter, while other freeze-resistant non-structural carbohydrates (NSCs) increase. Slight differences in NSC concentration between species are consistent with the differing climate sensitivity of the evergreen and deciduous species investigated. The general absence of differences between elevations suggests that the cambial activity of trees growing at the treeline was not limited by the availability of carbohydrates at the cambial zone but instead by environmental controls on the growing season duration.

How does climate influence xylem morphogenesis over the growing season? Insights from long-term intra-ring anatomy inPicea abies

“…The late summer temperature association is instead probably linked to carbon mobilization and deposition rates at the time of wall thickening (sink activity) (Hoch et al, 2002;Körner, 2015), which were apparently strongly related to temperature at high elevation. Our observations support previous findings that carbon fixation and carbohydrate mobilization are constrained by temperature at the altitudinal limit of a species (Hoch and Korner, 2003;Simard et al, 2013). Examples of this relationship are also given by observations that the long-lasting wall thickening process can be slowed or interrupted by reduced temperatures at the end of summer (Gindl, 1999;Vaganov et al, 2006;Xu et al, 2013), in extreme cases resulting in rings characterized by thin walls (known as light rings; Filion et al, 1986) or unlignified walls (known as blue rings; Piermattei et al, 2014) in the last cells.…”

Compound-Specific Carbon Isotopes and Concentrations of Carbohydrates and Organic Acids as Indicators of Tree Decline in Mountain Pine

“…More detailed information can be derived from the individual carbohydrates (sucrose, glucose, and fructose), and sugar alcohols (e.g., pinitol), but also from compounds like organic acids (malate and citrate) that are involved in more "downstream metabolic processes" leading to systematic but varying 13 C-enrichment of sink organs (such as stem) in comparison to leaves [20]. Thus far, there have been few investigations analyzing δ 13 C of individual carbohydrates and organic acids [19][20][21][22][23][24][25][26] using high-performance liquid chromatography (HPLC). However, even fewer investigations were applied in natural forest ecosystems to address questions of tree eco-physiology [19,22,23,26,27].…”

“…Thus far, there have been few investigations analyzing δ 13 C of individual carbohydrates and organic acids [19][20][21][22][23][24][25][26] using high-performance liquid chromatography (HPLC). However, even fewer investigations were applied in natural forest ecosystems to address questions of tree eco-physiology [19,22,23,26,27]. Therefore, further studies are needed to understand how environmental changes impact δ 13 C values and concentrations of individual compounds at the leaf level in declining trees.…”

Xylogenesis: Coniferous Trees of Temperate Forests Are Listening to the Climate Tale during the Growing Season But Only Remember the Last Words!

“…Thus, this process depends mainly on the carbohydrates produced by photosynthesis, for which light is the indispensable energy source (Kozlowski and Pallardy, 1997). However, wall thickening involves numerous and complex metabolic processes, which are considered the most sensitive to temperature among all the physiological processes related to tree carbon balance (Donaldson, 2001;Körner, 2003;Simard et al, 2013;Cuny et al, 2015). Finally, we expect that the environmental factors influence the rate of the processes, which directly reflects the physiological state of the plant as well as the influence of the environment, rather than their duration, which is tightly associated with genetic control and developmental constraints (Uggla et al, 1996(Uggla et al, , 2001Tuominen et al, 1997).…”