Abstract
The main aim of this paper is to present how the leaf sheath concerns internode elongation in rice, using the japonica cultivar Sasanishiki. Leaf sheaths were removed at the begining of the rapid elongation of the second internode, namely, the booting stage. Removal of a whole leaf sheath induced a marked growth inhibition of the first and second internodes. This inhibiting effect caused by the complete removal of the leaf sheath was just partly recovered only gibberellin A3 was applied. On the other hand, the effects of partial removal of the leaf sheaths are reversed by covering the internode itself or the whole panicle with aluminium foil or wrap film. These results suggest that the leaf sheath may act as a protective cover with regard to environmental stress in the young internodes and may help the tissue of the second internodes to retain the ability to respond to the endogenous gibberellin. The leaf sheath, especially that of the first leaf (flag leaf), may also stimulate the elongation of the first and second internodes through the enhancement of endogenous gibberellin production in the young panicles that are covered with these leaf sheaths.
