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

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Maunoury-Danger, Florence | Bathellier, Camille | Laurette, Julien | Fresneau, Chantal | Ghashghaie, Jaleh | Damesin, Claire | Tcherkez, Guillaume

Edité par CCSD ; Wiley -

International audience. The δ13C (carbon isotope composition) variations in respired CO2, 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 13C‐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 13C‐enriched compared with source tuber‐sucrose, suggesting that sucrose translocation from tuber to sprouts fractionated against 12C. However, both apparent fractionations were explained by the consumption of 13C‐depleted carbon for respiration or growth that enriched in the 13C 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 13C‐depleted pool. We therefore conclude that any fractionation at either the starch breakdown or the sucrose translocation level is unlikely under our conditions.

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