Effect of gibberllin application on sink strength and remobilization of wheat cultivars under terminal drought stress

Hormones play an important role in grain filling regulation (as a reproductive sinks) and the demand for assimilates from current photosynthesis and remobilization sources as well. The objective of this study was to improve sink strength through GA3 application, measuring remobilization and yield under terminal drought stress. Twenty wheat cultivars were cultivated in a split split plot arrangement based on RCBD design with three replications, full irrigation and 40% of field capacity being main plots, GA3 foliar application (60 μM) and control (No GA3) were regarded as sub-plots and wheat cultivars were sub-sub-plots. Grain yield, biological yield, yield components and remobilization (by internodes) were estimated. Significant variation among cultivars was observed under both full irrigation and stress treatments. However, the response of the cultivars to the gibberellin application was almost the same. Drought stress reduced grain yield (33%), biological yield (20%), 1000-seed weight (14%), number of grains per spike (14%) and remobilization (8%), but application of gibberellin increased these traits under both conditions. Gibberellin foliar application at the wheat pollination stage had a positive effect on sink strength and remobilization, especially under full irrigation conditions. Under drought stress conditions, the positive effect of gibberellin application on the studied traits was less due to the reduction of grain filling period. Based on the results of present experiment, foliar application of gibberellin is not recommended under drought stress conditions.