The following measurements were recorded: length of stem and leaf number at the start and end of experiments; days until flower buds became visible; and number nodes per at flower- ing. If no flower buds were visible by the end of the experiment, shoot tips were dissected under a stereoscopic microscope, and the number of leaf primordia and floral stage were recorded. The stage of floral development of each plant was indicated as follows: stage 0, vegetative shoot apex; stage 1, dome-shaped stage; stage 2, first stage of involucre formation; stage 3, final stage of involucre