In situ assessment of seasonal variation of assimilated carbon transfer to biochemical compounds by tracing 13C after pulse labelling on Quercus petraea
Résumé
Allocation of assimilated carbon among organs and more specially to biochemical compounds is affected by the
environment and affects tree growth, the contribution of each organ to autotrophic respiration, and, in fine, carbon
sequestration in the ecosystem.
The aim of this study (ANR CATS) was to assess the seasonal evolution of the contribution of assimilated carbon
to leaf, stem and root biochemical compounds and the contribution of photo-assimilates to leaf exportation and
autotrophic respiration. In situ 13C pulse labeling of 10–15 m tall trees was conducted in the field on six sessile
oak (Quercus petraea) throughout the growing season (i.e. in May, July and September). Leaf, stem and root 13C
content of starch, soluble sugars, structural matter and total organic matter was analyzed during 30 days after
labeling. 13C content in leaf respired CO2 was also determined
In leaves, the proportion of 13C allocated to total organic matter decreased in average by 48% during the first
3 days after the three labeling date. The proportion of leaf respired 13C stayed stable at 4% of total recovered
13C all along the season. Leaves exported the main part of assimilated 13C to other compartments during the 3
days after labeling with an hourly export rate comprised between 0.5 and 0.8 %. Whatever the labeling date, 6
hours after labeling, in leaves, 60% of labeled organic matter corresponded to starch, soluble sugars and structural
matter. In May, this proportion remained similar 30 days after labeling date. However partitioning between each
biochemical fraction changed : during the 6 first days after labeling, starch corresponded to the most labeled
compound, thereafter structural matter became the more labeled : it reveals the use of starch for leaf growth at this
period. For July and September labeling, the proportion of labeling organic matter corresponding to starch, soluble
sugars and structural matter decrease to 50 and 40% respectively, until day 30 after labeling. In this fraction, the
allocation to structural matter increase to 30% and 20 % respectively for July and September labeling. For those
dates, 13C also participated to construction of the leaves but in a lower extent: it progressively diminishes along
the season.
In stems and roots, the proportion of 13C allocated to starch, soluble sugars and structural matter increased from
40 % to 80% whatever the season from the first day after labeling to day 30. For May and July labeling, the
allocation to structural matter significantly increased: from 10 % the first day after labeling to 70 % the day 30
after labeling. 13C assimilated in May and in July contribute to the structure of stems and roots. For September
labeling, allocation of 13C to starch clearly increased from 5 % to 25 % during the month after labeling and
showed the priority to reserve accumulation at this period.
This type of study allow determination of allocation to metabolites and exportation rates which are rarely studied
Domaines
Biologie végétaleOrigine | Fichiers produits par l'(les) auteur(s) |
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