Influence of Sink Size on 15N and 13C Allocation during Different Phenological Phases of Spring Wheat Cultivars

Abstract

The scientific objective of this study was to answer the question of whether sink limitation is also true for high quality wheat varieties. We examined the incorporation of 15N and 13C during phenological phases into vegetative parts and grains of Elite wheat Triso (E) and Quality wheat Naxos (A) when the spike is halved. Three splits of fertilizer were applied at EC 11, EC 30, EC 59, whereby 10% at EC 30 and EC 59 was 15N, and plants were also labelled with 13CO2. The application of only the third split as 15N, combined with spike-halving, resulted in a significantly higher 15N-content (+11%) of 0.486 mg 15N/g DM, compared to the control (0.437 mg15N/g DM). Labelling whole plants with 13CO2 at EC 59 resulted in a significantly higher 13C-content—40%—(0.223 mg 13C/g DM) of the grains of the control for Triso at the fully-ripe stage (EC 89), compared to Naxos (0.160 mg 13C/g DM). This superiority was reduced to 34%, and was also demonstrated by spike-halving (0.226 mg 13C/g DM, 0.169 mg 13C/g DM). Remobilization of 15N for control and spike-halving treatments were 68.2% and 61.1%, respectively. This clearly demonstrates that the reduction of the sink size by spike-halving leads to a 7% reduction in the remobilization of 15N from vegetative to reproductive tissues.