The effects of NH4-N and plant growth regulators on Phalaenopsis spiking and flowering.

In Phalaenopsis production, year around flowering is possible by temperature control. However, the cost of heating and cooling is high and the development of energy saving methods is a major concern. In this experiment, effects of nitrogen fertilizer and plant growth regulators (PGRs) on spiking were investigated. Nutrient solutions containing 26.2 mg/L NH 4 -N and 82.7 mg/L NO 3 -N (control), control + 140 mg/L NH 4 -N, or control + 140 mg/L Urea-N was applied weekly. Application of excess NH 4 -N delayed flowering by approximately two weeks. Urea-N showed no clear effects on delaying spiking. Naphthalene acetic acid sodium salt (NAA˙Na), Benzyladenine (BA), Thidiazuron (TDZ), gibberellin A 3 (GA 3 ) or s-abscisic acid (s-ABA) was applied to investigate the effects on spiking. Among the PGRs tested, weekly (6 to 16 times) or biweekly (6 to 10 times) applications of 1,000 mg/L NAA˙Na delayed spiking of Phalaenopsis. S-ABA also delayed spiking, more by 6 weekly applications. GA 3 and BA showed no clear effects. TDZ stimulated vegetative or reproductive lateral bud growth markedly, depending on the air temperature. Combined application of NH 4 -N and NAA˙Na 23 times showed clear additional inhibitory effect on spiking. Combined application of NH 4 -N and s-ABA affected inflorescence growth differently, depending on the s-ABA concentrations. To elucidate an efficient and practical NAA˙Na application method, application with a Finnpipette, sprayer, alginic acid or Gelrite gel pellets containing NAA˙Na were experimented. Application with a Finnpipette was the most effective, followed by a sprayer. Application by alginic acid gel showed slight effects, but Gelrite gel showed no effects.