Phalaenopsis is the most important potted orchid around the world, with a fast-growing market (Wang, 2004). It is a monopodial epiphytic orchid, having indeterminate inflorescences. Phalaenopsis spike (bolt) and bloom under conditions of proper temperature and light after the plants have matured (Lee and Lin, 1984; Wang, 1995). The potential flower spikes usually emerge at the axils of the third and/or fourth basipetal mature leaf (Lee and Lee, 1996).
Phalaenopsis can only be sold on the retail market when in bloom. The ability of phalaenopsis to spike and bloom under inductive environmental conditions is highly correlated with its leaf size, but there is a significant difference among various hybrids (Lee, 1991). It is important to program phalaenopsis to bloom when the market demand is the greatest, such as at Chinese New Year, Valentine's Day, Mother's Day, Christmas, etc.
The period from spiking to first open bloom is unaffected by factors such as lighting, photoperiodism, and fertilizer when the temperature is held constant (Lin and Lee, 1998; Wang and Hsu, 1994). Because spiking precedes flowering in phalaenopsis, controlling spiking becomes the focus for the effective control of the flowering time of this orchid. The application of plant growth substance may be one solution to controlling spiking (Wang, 1995). Phalaenopsis is unable to spike and bloom at high temperatures (Lee and Lin, 1984; Wang et al., 2006). If a spiked phalaenopsis plant is moved to a high-temperature environment (30 °C) before its inflorescence differentiation, it will not produce flowers. This situation may be related to the decline of gibberellic acids (GAs) and cytokinin concentration in the developing flower stem (Chen et al., 1994; Chou et al., 2000). Using plant growth substances such as GA3 or N-6-benzyladenine (BA) separately at high temperatures failed to induce phalaenopsis to spike or bloom (Chen et al., 1994, 1997; Kubota et al., 1997). However, Chen et al. (1994) injection of GA3 into phalaenopsis plants that had already developed 3- to 5-cm-long floral spikes initialed at a cooler temperature resulted in flowering at high temperature (30 °C).
At lower temperatures (25/20 °C), treating phalaenopsis with GA3 resulted in long flower spikes and higher flower count. However, the petals are relatively thin, and lopsided flowers are easily generated (Lin, 1994). Spraying phalaenopsis with BA at a low temperature resulted in more flowers and flower spikes (Ho and Yang, 1990; Lin, 1994). Spraying BA on phalaenopsis when the first visible flower bud occurs led to more flowers with larger flower diameters and relatively thicker petals. However, the percentage of flower bud abortion increased (Lin, 1994).
The objective of this study was to investigate the feasibility of using BA in the regulation of phalaenopsis flowering to increase the spiking percentage, the spike, and flower count of phalaenopsis.
Chen, W.S., Chang, H.W., Chen, W.H. & Liu, Y.S. 1997 Gibberellic acid and cytokinin affect Phalaenopsis flower morphology at high temperature HortScience 32 1069 1073
Chen, W.S., Liu, H.Y., Liu, Z.H., Yang, L. & Chen, W.H. 1994 Gibberellin and temperature influence carbohydrate content and flowering in Phalaenopsis Physiol. Plant. 90 391 395
Chou, C.C., Chen, W.S., Huang, K.L., Yu, H.C. & Liao, L.J. 2000 Changes in cytokinin level of Phalaenopsis leaves at high temperature Plant Physiol. Biochem. 38 309 314
Ho, F.W. & Yang, L. 1990 Effects of plant growth regulators on the growth and flowering of Phalaenopsis Annu. Rept. Taiwan Sugar Res. Inst. 1989–90 17 18
Kubota, S., Hamotsu, H., Kazuo, I. & Masaju, K. 1997 Effect of light condition and GA3 application on development of axillary buds during low temperature treatment in Phalaenopsis J. Jpn. Soc. Hort. Sci. 66 581 585
Lee, N. 1991 Juvenility in Phalaenopsis. Proc. 2nd Symp. on Regulating the Production Period of Horticultural Crops Taichung District Agr. Expt. Sta Special Issue 23. 77 86
Lee, N. & Lin, G.M. 1984 Effect of temperature on growth and flowering of Phalaenopsis white hybrid J. Chinese Soc. Hort. Sci. 30 223 231
Lee, N. & Lee, J.H. 1996 Changes in carbohydrates in Phalaenopsis flower induction and inflorescence development J. Chinese Soc. Hort. Sci. 42 262 275
Lin, Y.R. 1994 Effect of light, temperature and plant growth regulators on flowering of Phalaenopsis spp. Graduate Institute of Horticulture National Taiwan University Taipei, Taiwan Master's thesis.
Lin, Y.R. & Lee, N. 1998 Light requirement of Phalaenopsis prior to and after cool-temperature forcing J. Chinese Soc. Hort. Sci. 44 463 478
Wang, Y.T. & Hsu, T.Y. 1994 Flowering and growth of Phalaenopsis orchids following growth retardant applications HortScience 29 285 288
Wang, Y.T., Tsai, W.T. & Dai, T.E. 2006 Heavy shading: An effective, low-cost alternative to high temperatures for inhibiting spiking in Phalaenopsis Proc. Taiwan Intl. Orchid Symp 164 173