Dynamics of Nitrogen Uptake and Mobilization in Field-grown Winter Oilseed Rape Brassica napus from Stem Extension to Harvest I. Global N Flows between Vegetative and Reproductive Tissues in Relation to Leaf Fall and their ResiduReport as inadecuate




Dynamics of Nitrogen Uptake and Mobilization in Field-grown Winter Oilseed Rape Brassica napus from Stem Extension to Harvest I. Global N Flows between Vegetative and Reproductive Tissues in Relation to Leaf Fall and their Residu - Download this document for free, or read online. Document in PDF available to download.

1 PIAF - Laboratoire de Physique et Physiologie Intégratives de l-Arbre Fruitier et Forestier 2 EVA - Ecophysiologie Végétale, Agronomie et Nutritions 3 The University of Queensland Brisbane

Abstract : Background and Aims Despite its high capacity to take up nitrate from the soil, winter oilseed rape Brassica napus is characterized by a very low N recovery in the reproductive tissues under field conditions. A significant part of the N taken up is lost to the soil in dead leaves during the growth cycle. An accurate description of N dynamics at the whole plant level in each compartment under field conditions should lead to a better understanding of N allocation in B. napus and improvements in the nitrogen harvest index. Methods An experiment was conducted in field conditions using sequential weekly 15 N labelling to follow N uptake, partitioning and mobilization. Nitrogen labelling 2Á5 kg N ha À1 ; 10 % excess was analysed weekly from stem extension to harvest to distinguish between uptake of new N labelled and mobilized N unlabelled in the different plant components. Key Results and Conclusions N requirements for seed filling were satisfied mainly by N mobilized from vegetative parts about 73 % of the total N in pods. Determination of the endogenous N flow showed that there was net transfer of N to the pods by leaves 36 %, stem 34 %, inflorescences 22 % and taproot 8 %. Precise study of N flow from leaves at different nodes revealed the existence of two main groups of leaves in terms of their apparent capacity to mobilize N; 30–60 % and 70–80 % of peak N content occurring during flowering and pod filling, respectively. Moreover, the latter group was found to be the main source of endogenous N from leaves. The mobilization of endogenous N from these leaves was prolonged and concomitant with N accumulation in the pods. A complex pattern of N mobilization from the leaves, to vegetative or reproductive tissues, was revealed. These results will be used to model N partitioning during the growth cycle.

Keywords : Brassica napus Leaf node 15N labelling Dynamics Uptake Partitioning Mobilization





Author: Philippe Malagoli - Philippe Laine - Laurence Rossato - Alain Ourry -

Source: https://hal.archives-ouvertes.fr/



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