Vegetative Proliferations of Floral Spikelets in Oryza sativa L.: VI. Development of proliferated spikelets (propagules) by means of soil cultivation

Abstract

The experiment was carried out to observe the development of proliferated spikelets (propagules) in rice cultivated in flooded soil and attempts were made to discuss the significance of the development of propagules in the propagation of rice. The propagules used in the experiment were obtained from ears of two mutant strains (P0), one induced by ethylene imine on the cultivar of Akibare (strain II) and the other induced by X-ray irradiation on the cultivar Reimei (strain II). It was observed that three propagules, two from strain I and one from strain II, could produce roots and ears (P1) when transplanted in flooded soil. And each of them produced spikelets with same kind of abnormalities as those in P0 plants. Abnormalities observed in case of strain I were as follws; 1) Successive initiation of leaf-like glumes forming a leafy shoot from the base of the spikelet, 2) Initiation of adventitious roots at the basal portion of spikelets, 3) Remarkable elongation of empty glumes having more veins than the normal ones, and 4) Initiation of rachilla-like protuberance in the stems. In case of strain II abnormalities were, 1) Remarkable elongation of the lemma having more veins than the normal ones, 2) Aditional initiation of glumes at the inner portion of lemma and palea, and 3) Production of more number of pistils and lower numbr of stamens than the normal ones. Fertility of spikelets in P1 were very poor in case of both strains, specialy in case of strain II the spikelets were almost sterile. P1 S1 plants developed from the seeds of P1 plants in strain I had also the same morphological abnormalities in their spikelets as those of P0 and P1. Therefore, it was considered that the mutant characteristics in the spikelets of P0 were genetically fixed. In respect of propagation of rice by propagules initiated on the ears, a very interesting point needs mentioning that the plants produced from the propagules encircled their life cycles by the diplont nuclear phase only omitting its sexual phase which is related to the formation of pollens and egg cells and their fertilization. Considering the general tendency of the plant kingdom as a whole, the more the plant evoluted the longer becomes the diplont nuclear phase in the life cycle shortening the haplont ones, the propagules seemed to be one of the progressive type of propagations in seed plant. It will also not be overemphasized to mention that the vegetative propagation of rice by propagules would obviously compensate the sterility of the spikelets