Floral stem growth of Arabidopsis ecotypes. II. Short time scale events and evidence for ultradian rhythms

The extension rate of the first inflorescence node of four Arabidopsis ecot ypes was measured during light/dark or continuous light exposure and was fo und to exhibit oscillations that showed various ultradian rhythms. During t he processes Arabidopsis ecotypes growth rate displays ultradian rhythms wi th periods in the range of 18 to 72 min. The rate oscillations were not in relation with mechanical noise or environmental oscillatory conditions. Ind eed, our studies suggest that the oscillations in growth rate are endogenou s in their origin. Moreover than ultradian oscillations, each ecotype displ ayed special growth rate variations, after the transition from light to dar k or reciprocally. This could be assimilated as individual growth rate sign ature for the four different ecotypes.