The observation on floral organ differentiation of an alien species, Flaveria bidentis (L.) Kuntze.
The formation of scorpioid cyme, capitulum and floret of Flaveria bidentis was observed under scanning electron microscopy. The inflorescence was composed of the main axis with three order branches in a decussate arrangement. Scorpioid cymes (3-6) were developed at the apex of the main inflorescence axis as well as lateral axes. Each scorpioid cyme had 5-15 capitulums which consisted of 4-11 florets. For the floral development process, 5 petal primordia arose firstly, then 5 stamen primordia appeared, followed by 2 carpel primordia. In 2007, florescence was from late July to late September in Tianjin, China. In Mid July, the inflorescence primordia and floret primordia were formed and differentiated continually, and approximately 15 days after the initiation of flower bud differentiation, individual floret was well formed.