Source-sink relationship in wheat as affected by defoliation and spikelet removal

Abstract

The relationship between source and sink affects the accumulation of grain dry matter in crops such as wheat. Wheat is a plant of high economic importance. The leaves are known as the source due to the production of photosynthetic materials. Photosynthetic materials made by the leaves are stored inside the seeds and the seeds are called the sink. Laboratory and field experiments were conducted to assess the impact of defoliation intensity and spikelet removal on seed yield, yield components, and germination traits of produced seeds in wheat. At the field experiment, studied factors included defoliation intensities (removal of 0, ½, and all leaves per plant) and spikelet removal (½ spikelet removal, no spikelet removal). Seeds produced under maternal plant conditions were assessed at the laboratory experiment. Results showed that wheat, Pishtaz cultivar, reacted to source and sink manipulation. Complete defoliation with ½ spikelet removal causes dramatically reduction of stem and leaf weight and spike weight. Under no leaf removal, ½ spikelet removal reduced wheat seed yield. Defoliation intensity and ½ spikelet removal had no significant effect on seed germination traits.  Wheat, cv. Pishtaz had little ability in changing seed size as one of the factors of sink strength under high photosynthate so the cultivar is more sink- than source- limited. Keywords: germination, leaf removal, maternal plant environment, seed vigour, Triticum aestivum