Short-day-grown Arabidopsis thaliana satisfies the assumptions of the plastochron index as a time variable in development

A plastochron index (PI) based on a 3-mm leaf reference length was established for the Columbia-1 (Col-1) ecotype and the se (serrate) mutant of Arabidopsis thaliana for quantitative analysis of leaf development. The three underlying assumptions for PI establishment-early exponential leaf growth rate, similar relative growth rates (RGRs), and plastochrons between successive leaves-were tested. Under a 10-h day length, the three assumptions held for leaves 11-37 of Col-1 and for leaves 7-37 of se. The mean plastochron of se was about 1.5 times longer than that of Col-1, and the mean RGR of Col-l was about 1.25 times greater than that of se.