Studies on the Morphogenic Abnormalities in Rice Spikelets caused by a Low Temperature

Abstract

Vatious morphogenic abnormalities as shown in figures were observed in the rice spikelets which were grown under low temperature-day temperature 14-18°C and night temperature 14°C. Morphogenic abnormalities found in the spikelets may be summarized as followings: 1) changes of organs in number, especially increment in number, 2) remarkable phenomena of fusion of inter and/or intra organs of lodicules, stamens and ovaries, 3) appearance of organs of intermediate and bisexual structures, 4) changes in sex expression, promoting femaleness and depressing maleness, 5) continuance of vegetative growth in the spikelets with no formation of sexual organ, incepting only glume and branch primordia, 6) exposure of extraordinarily developed ovule or integument from ovary through the style canal, 7) frequent occurence of abnormally swelled tissue or organ, and 8) appearance of multi-floret spikelets, etc. From the results above mentioned it is considered that the morphogenic regulation in the meristematic tissue of spikelet primordia may become unstable and the disturbance of organ development tends to be occured, by the low temperature treatment. Some discussions were tried on the relationship between the appearance of morphogenic abnormalities due to a low temperature treatment and the level of some growth substances, auxins and gibberellin, in spikelet primordium, based upon the writers' experimental results previously reported.