Low levels of oxygen promote internodal elongation in floating rice independently of enhanced ethylene production

Abstract

Submergence induces rapid elongation of internodes in floating rice(Oryza sativa L. cv. Habiganj Aman II). The initial signalfor such internodal elongation has been considered to be the reduced partialpressure of oxygen in submerged internodal cavities, which promotes theelongation of internodes through the enhancement of ethylene synthesis. Weexamined the relationship between low oxygen pressure and ethylene production inthe rapid elongation of floating rice internodes using ethylene biosynthesisinhibitors, aminooxyacetic acid (AOA) and CoCl2. When floating ricestem segments were incubated in an atmosphere of low O2, internodalelongation accelerated and ethylene production increased. However, in stemsegments treated with AOA or CoCl2, low O2 stillstimulated the elongation of internodes although the ethylene production by theinternodes was less than by those in control stem segments where internodalelongation was not promoted. These results indicate that low O2 iscapable of causing rapid elongation of internodes of floating rice independentlyof enhanced production of ethylene. In addition to low O2,submergence, ethylene and gibberellic acid each enhanced the production ofethylene by internodal tissues, suggesting that enhanced ethylene production isa common phenomenon accompanied by the acceleration of internodal elongation infloating rice.