The relations between panicle characters of intersubspecific heavy panicle hybrid rice and vascular bundles in neck panicle

The characters of vascular bundle in neck panicle and grain filling of intersubspecific heavy panicle hybrid rice (IHPHR) were studied. The results were as follows: The IHPHR had more vascular bundles, much larger areas of single vascular bundle, much larger areas of all vascular bundles, much larger areas of all phloem and much larger areas of all xylem in neck panicle than intervarietial hybrid rice (IHR), which increased the number of the second branches and the number of grains in second branch and enlarged the panicle of IHPHR. IHPHR had a lower burdened capacity of spikelet number and matter to fill the grains in the conducting tissue than IHR. So, IHPHR had not only larger panicle but also normal grain filling and heavier panicle. IHPHR overcame the main physiological barriers of intersubspecific hybrid rice-large panicle but limited flow of photosynthetic product to the panicle that led to poor grain plumpness. The results also indicated that the breeding of IHPHR was a effective measure for the rice breeding of super high yield.