Elongation of the Uppermost Internode for Changxuan 3S, a Thermo-Sensitive Genic Male Sterile Rice Line

Changxuan 3S, a thermo-sensitive genic male sterile (TGMS) rice line with eui gene, is derived from the TGMS rice line Pei'ai 64S by irradiation with 350 Gy of 60Co γ-ray. To elucidate the uppermost internode elongation of the TGMS line with eui gene, Changxuan 3S and its parent Pei'ai 64S were used to study the effects of temperature on panicle exsertion. At 24°C, the uppermost internode of Changxuan 3S elongated the fastest from the 4th day before flowering to 0 day (flowering), being 2.1-fold as that of Pei'ai 64S, whereas it elongated slowly during the 12th day to the 4th day before flowering and the 1st to the 3rd day after flowering. The uppermost internode of Changxuan 3S exserted from the flag leaf sheath at 22°C, 24°C and 26°C, and the length of elongated uppermost internode increased with the decreasing temperatures. At 28°C, though the panicles of Changxuan 3S were still enclosed in the leaf sheath, the degree of panicle enclosure was significantly lower compared with Pei'ai 64S. Cytological studies on Changxuan 3S showed that the uppermost internode elongation was attributed to the increase of cell number and cell elongation, and the latter was more significant. Moreover, the numbers of outermost and innermost parenchyma cells and the cell length of the uppermost internode reduced with the increasing temperatures.