EFFECT OF GROWTH RETARDANT UNICONAZOL ON THE FLORET FORMATION OF ZINNIA-ELEGANS JACQ

This experiment was conducted to determine the effect of Uniconazol on the morphological response particularly the formation of ray and tubular florets in Zinnia elegans Jacq. which include the tall cultivar Red Sun as well as dwarf cultivars such as Peter Pan Scarlet, Peter Pan Golden, Dreamland Scarlet and Dreamland Yellow. In addition, the effects of other growth retardants such as Ancymidol, CCC and SADH on cultivar Red Sun were also investigated. Growth retardation induced by Uniconazol treatment was more prominent in dwarf cultivars than the tall cultivar Red Sun. In all cultivars treated with Uniconazol, the number of days to flowering was delayed 3 appoximately 4 days and the flower fresh weight was reduced to less than half of control. The number of ray florets was decreased and tubular florets was increased by Uniconazol treatment in all cultivars especially in 'Red Sun'. Growth retardation induced by Uniconazol was stronger than other growth retardants. The number of days to flowering were delayed 1.4, 2.5 and 3.6 days by Uniconazol, CCC and SADH treatments, respectively. The flower fresh weight was reduced to less than half of control due to Uniconazol, CCC and SADH treatments. All growth retardant treatments except Ancymidol reduced ray floret and increased tubular floret. As a result, the plants treated with growth retardants produced single and half-double flowers.