Alteration of Wheat Source-Sink Relation by Nitrogen and Spikelet Removal

The source and sink relationships determine the amount and distribution of biomass in plants. Field and laboratory experiments were conducted to study the effect of nitrogen rate and spikelet removal on seed yield and germination traits of wheat. The field experiment was conducted employing sink manipulation (no spikelet removal and ½ spikelet removal) and source manipulation (nitrogen rate of 0, 75, and 150 kg ha-1). This study was performed as a factorial experiment in a randomized complete block design with three replications. Seeds obtained from the field experiment were subjected to determine the effect of the sink and source manipulation on seed germination traits in the laboratory experiment. Results showed that most traits under study were not affected by source and sink manipulation. Seed yield and seed weight were not affected by spikelet removal and varying nitrogen applications. Although some of the wheat spikelets have been removed, those plants have been able to maintain the number of seeds per spike and the weight of a single seed. The use of nitrogen at the spike emergence stage did not affect the seed yield of the Pishtaz cultivar. Nitrogen needed for the seeds could be compensated by the re-mobilization of nitrogen from various plant organs such as the stem. Nitrogen application of 150 kg ha-1 with the removal of ½ spikelets improved seed germination (%) and vigor comparing control (no spikelet removal with no nitrogen application). Considering that seed yield and seed weight did not change under the influence of source and sink manipulation, it can be concluded that Pishtaz wheat is more sink-limited than source-limited.