Articles
SHORT- AND LONG-TERM CARBON ALLOCATION IN YOUNG WALNUT WITH TWO BRANCHES GROWN IN DIFFERENT LIGHT ENVIRONMENTS: A 13C – 14C DOUBLE TRACING EXPERIMENT
Article number
544_29
Pages
219 – 226
Language
English
Abstract
In order to investigate the effects of an heterogeneous within-crown light environment on carbon allocation, young scions of walnut (Juglans regia L.) cv.
Franquette were trained on two branches, one left in full sunlight and the other shaded resulting in a 67 % reduction in PAR. In September, the two branches were separately labeled with 14CO2 and 13CO2 respectively, so that the photosynthates from each branch could be traced independently at the same time.
Although some carbon movements could be detected within 5 days in both directions (including from the shaded branch to the sun branch), between-branch carbon movements were very limited: less than 1% of the diurnal net assimilation of a branch.
At this time of the year branch autonomy was nearly total, leading to increased relative respiratory losses and a moderate growth deficit in the shaded branch.
However, more significant carbon import movements into the branches occurred in winter, possibly representing up to 10 % of total branch reserves, which makes branch autonomy more questionable at this time scale.
It was even more so regarding reserve mobilization in spring, as new shoots from both branches got carbon mobilized from the whole plant.
From these results, the branch autonomy concept appeared valid for photosynthate allocation in the photosynthetically active season, however no rapid conclusion should be derived regarding the subsequent viability of new shoots the following seasons.
New shoots have a new opportunity to develop in spring, even though the bearing shoot was developed under adverse conditions.
As phloem is considered not functional in winter, it is suggested that xylem is involved as the pathway for carbohydrate movements at this time of the year.
This is in agreement with other results regarding sugar exchanges between the xylem vessels and the neighboring reserve parenchymas.
Franquette were trained on two branches, one left in full sunlight and the other shaded resulting in a 67 % reduction in PAR. In September, the two branches were separately labeled with 14CO2 and 13CO2 respectively, so that the photosynthates from each branch could be traced independently at the same time.
Although some carbon movements could be detected within 5 days in both directions (including from the shaded branch to the sun branch), between-branch carbon movements were very limited: less than 1% of the diurnal net assimilation of a branch.
At this time of the year branch autonomy was nearly total, leading to increased relative respiratory losses and a moderate growth deficit in the shaded branch.
However, more significant carbon import movements into the branches occurred in winter, possibly representing up to 10 % of total branch reserves, which makes branch autonomy more questionable at this time scale.
It was even more so regarding reserve mobilization in spring, as new shoots from both branches got carbon mobilized from the whole plant.
From these results, the branch autonomy concept appeared valid for photosynthate allocation in the photosynthetically active season, however no rapid conclusion should be derived regarding the subsequent viability of new shoots the following seasons.
New shoots have a new opportunity to develop in spring, even though the bearing shoot was developed under adverse conditions.
As phloem is considered not functional in winter, it is suggested that xylem is involved as the pathway for carbohydrate movements at this time of the year.
This is in agreement with other results regarding sugar exchanges between the xylem vessels and the neighboring reserve parenchymas.
Publication
Authors
A. Lacointe, T. Améglio, F.A. Daudet, J.S. Frossard, B. Saint-Joanis, M. Vandame, B. Adam, C. Bodet, M. Crocombette, S. Ploquin, E. Deléens, C. Lelarge, G.C. Song
Keywords
assimilate partitioning, heterogeneous environment, labeling, carbohydrates, winter redistribution, branch autonomy, Juglans regia L.
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