Studies on Abnormal Hypertrophy of Tapetum caused by Auxins in Rice Plants, especially in Relation to that caused by Low Temperature

Abstract

It is well known phenomenon that abnormal hypertrophy of tapetum takes place in rice plants encountered with an unfavourable low temperature. In a previous paper we have discribed the phenomenon of abnormal hypertrophy of tapetum might be an incidence controlled by the level of endogenous auxin during the anther development. This experiment was carried out with the purpose to prove if exogenously supplied auxins can induce the same abnomral hypertrophy of tapetum as that caused by the low temperature. Naphthaleneacetic acid (NAA) and 2, 4-dichlorophenoxyacetic acid (2, 4-D) were used at concentrations of 0.1, 1.0 and 10.0 ppm. The young spikes at the period of first and second constructions of micrspores were floated on the solution of chemicals for 24 hr at room temperature. Then the anthers were fixed in FAA and prepared for histological observations by means of the usual paraffin method sectioning about 10μ in thickness. Various types of tapetal abnormalities as shown in figs. 2∼17 were observed in the anthers treated with auxins, especially in the plots of the higher concentrations. Thus it became clear that the auxins used obviously induce or promote the same tapetal hypertrophy as that caused by the low temperature. These results seem to support the concept previously reported by the writers that appearance of the tapetal hypertrophy under the low temperature might have a close relationship with the endogenous level of auxin during the anther development. The interaction between auxins and RNA in connection with the abnormal development of tapetum was discussed quoting Dr. Shibuya's experimental result that the tapetal abnormality was induced by application with uridine-monophosphate or triphosphate plus glucose-1-phosphate.