Morphophysiological changes and effects of exogenous plant growth regulators on the flower development of Siam tulip (Curcuma alismatifolia)

Abstract The Siam Tulip (Curcuma alismatifolia Gagnep.) is a tropical ornamental plant capable year-round growth. However, its natural flowering is limited to the rainy season, thereby limiting its commercial viability as a continuously flowering ornamental crop. This study analyzed the morphological and physiological changes during the growth and development of plant propagated from corms and evaluated the the effects of exogenous plant growth regulators on flower development in both juvenile and mature plants. The flower development of Siam Tulip can be divided into two distinct phases: (1) the floral transition phase (day 18 - 30), and (2) the flower development phase (day 30 to 72). The flower development included (i) floral organs formation and development (day 30 - 62), and (ii) inflorescence elongation and blooming (day 62 - 72). Levels of auxin, gibberellin, and cytokinin progressively increased from the vegetative to the reproductive stage, peaking during the late inflorescence development whereas abscisic acid levels rose from the vegetative phase to the floral meristem formation but gradual decline thereafter. Application of 20 mg L-1 indole-3-acetic acid (IAA) or 10 mg L-1 benzyladenine (BA) significantly accelerated floral initiation in juvenile plants and enhanced flower develoment in mature plants. Additionally, treatment with 20 mg L-1 gibberellic acid promoted the elongation of the inflorescence stem. These findings suggest that appropriate PGR treatments can effectively accelerate flowering in C. alismatifolia, thereby enhancing its commercial potential.