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

Dubousset, L., Etienne, P., Avice, J.C.
Journal of experimental botany 2010 v.61 no.15 pp. 4313-4324
Brassica napus var. napus, bolting, buds, developmental stages, filling period, leaves, pods, rapeseed, roots, seed development, seed quality, seeds, source-sink relationships, stems, sulfates, sulfur, surveys, yield components
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 ³⁴SO[Formula: see text] and ¹⁵NO[Formula: see text] 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.