The effect of vascular system of spike on the yield and yield components of the Atrak wheat

For investigating the impact of the vascular transfer system of the main rachis on the yield and yield-components of Atrak wheat, an experiment was conducted in the Educational-Research site of the IAU, Saveh Branch, during 2008-2009 farming year. The internodes of the spike, the number and the size of the central vascular bundles, and the manner of their distribution were examined in this study. The results indicated a significant relationship between the number of spikelets on the rachis and the number of the central vascular bundles on its lower part. The number of the central vascular bundles decreased toward the upper parts of the rachis. This decrease was averagely about 0.5 vessels in each internode between the first to the fourth internodes in the lower part, 1.2 between the fifth to the fourteenth internodes in the central part, and 0.7 from the fifteenth internode to the terminal spikelet in the upper part. The size of the vascular bundles across the rachis decreased according to a special model. The largest portion of the vascular bundles were observed in the central part of the rachis and then in the lower and upper parts, respectively. There was a positive correlation between the number and weight of the grains and the number and size of the vascular bundles allocated to each spikelet across the rachis, given that the spikelets with the maximum average of grain weight and number, located on the central part of the spike, had the largest number and size of the vascular bundles compared to the spikelets on the other parts of the rachis.