Abstract
The objectives of this study were to clarify the interspecific variation on (i) the structure of spikelet and reproductive organs, (ii) the relationship between the size of spikelets and the reproductive organs, and (iii)the surface structure of anther. Oryza breviligulata had the longest spikelet and O. sativa had the shortest. O.sativa had the broadest spikelet and 0. meridionalis had the narrowest. 0. longistaminata had the longest anther while 0.breviligulata had the smallest. O. longistamenata had the longest stigma and 0. sativa had the smallest. The spikelet length had a significant positive correlation with the stigma, but it had almost no correlation with the anther length. The anther length and the stigma length had a positive significant correlation. The spikelet width and stigma length had a negative significant correlation. A difference in the degree of development of cuticular ridges on the anther surface was observed according to species, position of spikelet on a panicle and region in an anther. It was more dense on the surface of the upper region of an anther than on the lower one, and in the spikelets of higher position on a panicle than in those of lower position. The difference in the development of cuticular ridges on the anther surface due to spikelets position on a panicle was more conspicuous in wild species than in cultivated species.
