Remplissage en azote des siliques et des graines de colza (Brassica napus L.) : estimation des flux par marquage isotopique et caractérisation des protéines impliquées dans la mise en réserve

Oilseed rope (Brassica napus L.) is known for its high capacity to absorb mineral N from the soil profile and therefore can be grown as a catch crop to reduce nitrate leaching from arable cropping systems. However, the N harvest index of this crop is usually low, due in part to a low ability to remobilize N from leaves and to the fall of N-rich leaves which allows a significant amount of N to return to the environment. Our hypothesis of work was that the efficiency with which leaf N is mobilized to the seeds might be improved by increasing N storage within the plant through alternative sinks. It has, for example, been shown in both herbaceous and woody species that N con be transiently stored as vegetative storage proteins (VSP), which con be hydrolyzed to supply developing sinks with N. The objectives of this study were first, to quantify and distinguish by N-15 labelling between the origin of the N used for pod filling, namely from uptake or from vegetative tissue mobilization, secondly to describe the kinetic behaviour of different source tissues and, lastly, to identify some proteins that might be involved in N storage.