Effects of Gibberellin on the Morphogenesis in Rice Plants : 7. Cyto-histological abnormalities which appeared in spikelets.

Abstract

The effectd of gibberellin which was applied at the stage of panicle primordium differentiation on the rice spikelet morphogenesis were studied cyto-histologically. Newly observed cyto-histological abnormalities were as followings: 1) proliferation of various organs, 2) increase of vascular bundles in number, 3) disarrangement in the situation of organ development, 4) changes in relative position of organs due to the supernumerary organ initiation, 5) incomplete formation of anther loculi and abnormal development of tapete tissues, 6) occurrence of pistils with a normal and an incompletely formed loculi, 7) outgrowth of integuments (?) through the style canal, 8) appearance of concrescence phenomena of low degree etc. As for the increment of organs and vascular bundles in number, two cases have been clarified; one is the additional differentiation of the organs or tissues which were not seen in the normal spikelet, and the other is the well development of the degenerated organs or tissues in the process of phyllogeny or ontogeny. It was considered that such phenomena as incomplete separation of anther loculi, imperfect formation of anthers due to the feminization of androecium, abnormal development of tapete tissue and indehiscence of anthers etc. must be caused fundamentally by a same physiological background in the spikelet morphogenesis. Some discussions were tried on the formative process of two-loculi ovary based on the transformative phenomena of additional carpellary leaves to ovary. The phenomenon of an unusual development of the internal tissues of ovary was considered to be brought about by a so-called "flower vegetativation" in floral organs.