Age, allocation and availability of nonstructural carbon in mature red maple trees

Abstract

SummaryThe allocation of nonstructural carbon (NSC) to growth, metabolism and storage remains poorly understood, but is critical for the prediction of stress tolerance and mortality.We used the radiocarbon ( 14 C) 'bomb spike' as a tracer of substrate and age of carbon in stemwood NSC, CO 2 emitted by stems, tree ring cellulose and stump sprouts regenerated following harvesting in mature red maple trees. We addressed the following questions: which factors influence the age of stemwood NSC?; to what extent is stored vs new NSC used for metabolism and growth?; and, is older, stored NSC available for use?The mean age of extracted stemwood NSC was 10 yr. More vigorous trees had both larger and younger stemwood NSC pools. NSC used to support metabolism (stem CO 2 ) was 1-2 yr old in spring before leaves emerged, but reflected current-year photosynthetic products in late summer. The tree ring cellulose 14 C age was 0.9 yr older than direct ring counts. Stump sprouts were formed from NSC up to 17 yr old. Thus, younger NSC is preferentially used for growth and day-to-day metabolic demands. More recently stored NSC contributes to annual ring growth and metabolism in the dormant season, yet decade-old and older NSC is accessible for regrowth.

Nonstructural Carbon in Woody Plants

“…The ages of sugar and starch were similar, implying regular interconversion between these compounds. Similar results were found in Acer rubrum L., where NSC age increased with the age of the tree; however, comparatively younger NSC was found in more vigorous trees (12). Ten-year-old NSC was allocated to new root growth following a major hurricane disturbance in a dry tropical forest (139), red maple stump sprouts were grown from remobilized NSC in roots as old as 17 years (12), and new roots in desert palms were produced from remobilized NSC as old as >60 years (R. Vargas, C. Czimczik, S. Bullock, X. Xu & S. Djuricin, unpublished data).…”

“…Similarly, resprouting requires the use of belowground NSC to rebuild both stem and foliage, and observations suggest that plants are able to draw upon much older NSC reserves to do so than they commonly use for annual growth and maintenance (12). Observations suggest that obligate resprouters are actively storing NSC.…”

“…New roots, leaf buds, and flowers grow from stored NSC up to two years old (52,139), and stored NSC up to three or four years old has been incorporated into tree ring cellulose growth (54,65). NSC used for root (14,22,51) and stem (12,87) respiration can be several years old.…”

The Role of Xylem Parenchyma in the Storage and Utilization of Nonstructural Carbohydrates

“…The sapwood NSCs have been analyzed in a number of ecological studies (Hoch et al 2003 ;Sauter and Wellenkamp 1998 ;Ashworth et al 1993 ;Palacio et al 2007 ;Carbone et al 2013 ), providing insights into the size and dynamics of the wood parenchyma carbohydrate pool. In the following sections, we will review the NSC accumulation patterns observed in different tree species and different woody organs and discuss changes in NSC concentration and composition that occur throughout the growing season.…”

Geographic pattern and effects of climate and taxonomy on nonstructural carbohydrates of Artemisia species and their close relatives across northern China

“…NSCs provide an essential buffer against fluctuations in carbon (C) supply and C demand for plants and can be used in various ways, such as supporting plant metabolism, promoting new tissue growth, producing protective compounds or storing C for future use (Chapin et al 1990;Herms and Mattson 1992;Carbone et al 2013;Piper and Fajardo 2014). Allocation of NSC to storage tissues by plants can be either a passive process, when C supply exceeds C demands (Chapin et al 1990), or an active process, when NSC is stored at the expense of growth (Wiley and Helliker 2012).…”