Is the remobilization of S and N reserves for seed filling of winter oilseed rape modulated by sulphate restrictions occurring at different growth stages?

How the remobilization of S and N reserves can meet the needs of seeds of oilseed rape subject to limitation of S fertilization remains largely unclear. Thus, this survey aims to determine the incidence of sulphate restriction [low S (LS)] applied at bolting [growth stage (GS) 32], visible bud (GS 53), and start of pod filling (GS 70) on source–sink relationships for S and N, and on the dynamics of endogenous/exogenous S and N contributing to seed yield and quality. Sulphate restrictions applied at GS 32, GS 53, and GS 70 were annotated LS32, LS53, and LS70. Long-term 34SO42− and 15NO3− labelling was used to explore S and N partitioning at the whole-plant level. In LS53, the sulphur remobilization efficiency (SRE) to seeds increased, but not enough to maintain seed quality. In LS32, an early S remobilization from leaves provided S for root, stem, and pod growth, but the subsequent demand for seed development was not met adequately and the N utilization efficiency (NUtE) was reduced when compared with high S (HS). The highest SRE (65±1.2% of the remobilized S) associated with an efficient foliar S mobilization (with minimal residual S concentrations of 0.1–0.2% dry matter) was observed under LS70 treatment, which did not affect yield components

Remobilization of leaf S compounds and senescence in response to restricted sulphate supply during the vegetative stage of oilseed rape are affected by mineral N availability

The impact of sulphur limitation on the remobilization of endogenous S compounds during the rosette stage of oilseed rape, and the interactions with N availability on these processes, were examined using a long-term 34SO42− labelling method combined with a study of leaf senescence progression (using SAG12/Cab as a molecular indicator) and gene expression of the transporters, BnSultr4;1 and BnSultr4;2, involved in vacuolar sulphate efflux. After 51 d on hydroponic culture at 0.3 mM 34SO42− (1 atom% excess), the labelling was stopped and plants were subject for 28 d to High S-High N (HS-HN, control), Low S-High N (LS-HN) or Low S-Low N (LS-LN) conditions. Compared with the control, LS-HN plants showed delayed leaf senescence and, whilst the shoot growth and the foliar soluble protein amounts were not affected, S, 34S, and SO42− amounts in the old leaves declined rapidly and were associated with the up-regulation of BnSultr4;1. In LS-LN plants, shoot growth was reduced, leaf senescence was accelerated, and the rapid S mobilization in old leaves was accompanied by decreased 34S and SO42−, higher protein mobilization, and up-regulation of BnSultr4;2, but without any change of expression of BnSultr4;1. The data suggest that to sustain the S demand for growth under S restriction (i) vacuolar SO42− is specifically remobilized in LS-HN conditions without any acceleration of leaf senescence, (ii) SO42− mobilization is related to an up-regulation of BnSultr4;1 and/or BnSultr4;2 expression, and (iii) the relationship between sulphate mobilization and up-regulation of expression of BnSultr4 genes is specifically dependent on the N availability

Programme PHYTOREF. Etablissement d'un référentiel pour les méthodes chimiques de diagnostic des risques liés à la phytodisponibilité des éléments en traces dans les sols. Etude de faisabilité

Convention ADEME *Laboratoire Sols et Environnement. ENSAIA-INPL/INRA. 2, av. de la forêt de Haye. BP 172. Vandoeuvre-Lès-Nancy cedex. France Diffusion du document : Laboratoire Sols et Environnement. ENSAIA-INPL/INRA. 2, av. de la forêt de Haye. BP 172. Vandoeuvre-Lès-Nancy cedex. FranceProgramme PHYTOREF. Etablissement d'un référentiel pour les méthodes chimiques de diagnostic des risques liés à la phytodisponibilité des éléments en traces dans les sols. Etude de faisabilit