Abstract: The mobilization of N from reserve organs (leaves, roots, branches and trunk) to developing new organs was studied at different moments of the growth cycle. Three-year-old Valencia Late orange trees (Citrus sinensis (L.) Osbeck) were grown individually outdoors in 150 L containers filled with siliceous sand. Trees were irrigated with a nutrient solution labelled with potassium nitrate with an enrichment of 4 atom 15N % excess during a complete growth cycle. At the following year, plants were irrigated with unlabelled nutrient solution, and harvested throughout the growth cycle (flowering, fruit set, second flush, third flush, and dormancy). Total N and 15N analyses were carried out in the different organs of the plants. The highest amounts of N were found in leaves and roots (33–42% and 30–38%, respectively). Distribution of 15N was similar to that obtained for total N (42 and 39% of total 15N in leaves and roots, respectively) as is expected after a long period of labelling. Old leaves were the main reserve organs, contributing a 40–50% of the total N exported. Roots and aerial woody tissues exported between 30–35% and 15–25% of total reserve N, respectively. N exported by old leaves was approximately 57% of the N accumulated during the preceding year, while roots translocated 40% and trunk plus branches 35%. More than 70% of N accumulated in new organs during spring came from N stored in old organs.

EXPLOR_STEP=$WICRI_ROOT/Wicri/Bois/explor/OrangerV1/Data/Main/Exploration

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   |wiki=    Wicri/Bois
   |area=    OrangerV1
   |flux=    Main
   |étape=   Exploration
   |type=    RBID
   |clé=     ISTEX:42E9AD698891AF5E730944C016DBA54286CD10D5
   |texte=   Mobilization of the reserve N in citrus
}}