Is there any ¹²C/¹³C fractionation during starch remobilisation and sucrose export in potato tubers?

Abstract

The delta(13)C (carbon isotope composition) variations in respired CO(2), total organic matter, proteins, sucrose and starch have been measured during tuber sprouting of potato (Solanum tuberosum) in darkness. Measurements were carried out both on tubers and on their growing sprouts for 23 days after the start of sprout development. Sucrose was slightly (13)C-depleted compared with starch in tubers, suggesting that starch breakdown was associated with a small isotope fractionation. In sprouts, all biochemical fractions including sucrose were (13)C-enriched compared with source tuber-sucrose, suggesting that sucrose translocation from tuber to sprouts fractionated against (12)C. However, both apparent fractionations were explained by the consumption of (13)C-depleted carbon for respiration or growth that enriched in the (13)C sucrose molecules left behind. In addition, whole tuber sucrose is constantly composed of recent sucrose from starch breakdown and old sucrose associated with an inherited, slightly (13)C-depleted pool. We therefore conclude that any fractionation at either the starch breakdown or the sucrose translocation level is unlikely under our conditions.

Changes in 13C/12C of oil palm leaves to understand carbon use during their passage from heterotrophy to autotrophy

“…leaflet replenishment), a rapid transition occurred with a 13 C-depletion of OM and an increase in chlorophyll content; and (iii) autotrophic leaves were 13 C-depleted suggesting they were mainly using photosynthates. Our results also confirmed the 13 C-depletion in autotrophic tissues (leaflets) compared to heterotrophic ones (rachis and petiole) already reported for other species, 16 but we showed huge changes during leaf development. The present results on the use of the carbon isotope composition for investigating the leaf growth and development at plant scale for oil palm open new insights into the carbon metabolism and allocation studies of other sink organs such as trunk, roots and bunches.…”

“…Another hypothesis is that adult autotrophic leaves (source) supplied carbon to young heterotrophic leaves with photosynthetic carbohydrates originally 13 C-depleted, which were then enriched in 13 C during remobilisation and transportation, as suggested by many authors. 11,15,16,24 Fructose was also believed to participate in leaf growth: its concentration in heterotrophic leaves was higher (from 3 to 7 mg g À1 DW) than that of other sugars. It might also participate through important translocation, perhaps from the first 12 autotrophic leaves to the leaves under elongation.…”

Woody tissue photosynthesis and its contribution to trunk growth and bud development in young plants

“…However, Bathellier et al . (2008) and Maunoury‐Danger et al . (2009) demonstrated that during ontogeny of Phaseolus vulgaris L. seeds and during sprouting of Solanum tuberosum tubers sucrose export was not associated with fractionation.…”

“…Considering the more general concept of carbon sources versus carbon sinks, another interesting study can be added for comparison. Maunoury‐Danger et al . (2009) found that when sprouting occurs in Solanum tuberosum tubers in the dark, sucrose δ 13 C in the heterotrophic sprouts (i.e.…”

“…(2009) demonstrated that during ontogeny of Phaseolus vulgaris L. seeds and during sprouting of Solanum tuberosum tubers sucrose export was not associated with fractionation. Maunoury‐Danger et al . (2009) alternatively explained this enrichment by arguing that 13 C depleted carbon is consumed in respiratory metabolism and in tissue synthesis of the sprout, resulting in a 13 C enrichment of sprout sucrose.…”