Relationship between Flower Formation and Elongation of Internodes in Wheat, as compared with Rice Plants

The experiments were carried out to study a relationship between flower formation and elongation of internode in cereals. In the present report, especially, the effects of temperature on flower formation and elongation of internode in wheat are concerned, and compared the wheat with the paddy rice plant from the standpoint of the flower formation and elongation of internode. In this experiment, wheat varieties NORIN No.53, YUYAKE KOMUGI and NORIN No. 64 were used as materials. Seeds of each variety were sown in two thermo-controlled green-house (0°∼14°C) or (5°∼30°C) and out of door (-5°C∼23°C) respectively. The flower-formation was indicated by the double-ridges stage of main shoot apex. The formation of vacant space was taken for a sign of elongation of internode as we had reported. Dissected stem tips were fixed in F. A. A. and were embedded in paraffin wax. Serial sections (cut at about 15μ) of them were stained with 1% gentian violet solution. In an early stage of vegetative growth, none of nodes was observed in the shoot apex. Nodes were observed at below the growing point of the apex after flower initiation. In all the experiment, the elongation of internodes began after the flower formation. However, in all the varieties, flower formation and elongation of internodes were accerelated by high temperature. Namely, flower formation and elongation of internodes in NORIN No. 53 occurred on 39 days after planting in green house of high temp. and 114 days after planting in out of door of low temp. But, no alteration in this order of flower formation and elongation of internode was recognized by applying high or low temperature. Thus, it became clear that there is a difference in the formation of the flower and elongation of the internodes between wheat and paddy rice. As we had reported already, the initiation of internode elongation in paddy rice plants takes place before the flower formation, and the elongation of internodes seems to be independent to the flower formation. On the contrary, the initiation of internode elongation in wheat occurred after the flower initiation under all the different conditions. Thus, we may conclude that there is a closer relation between flower formation and beginning of elongation of internodes in wheat than paddy rice plants.