Light sum, nitrogen level and growth retardant effects on flower and nectar production in Stachytarpheta frantzii
The effects of light, nitrogen and plant growth retardants on flower and nectar production in 'Stachytarpheta franatii' Polak. were examined. Light sums treatments were 100% (April-June greenhouse conditions); 27%, 43% or 77% light (shade cloth); or 125% light (supplemental lighting). Nectar increased with light sum. The ratio of sucrose/(glucose+fructose) was highest under 100% light. The number of florets/day was maximized at 75% light. Nitrogen concentrations of 50, 100 and 200 ppm N were tested in the summer and winter. In the summer, nitrogen level affected nectar concentration. Total nectar volume and sugar produced/spike decreased with nitrogen concentration. Ancymidol (0.5-2.5 mg/pot), paclobutrazol (0.5-2.5 mg/pot) and chlormequat (0.25-0.75 g/pot) were used as a drench in the summer and winter. Ancymidol and paclobutrazol had a negative effect on flowering and nectar production. Chlormequat (0.75 g/pot) increased days to flower, flowering period and total nectar volume and sugar produced/spike in summer. Chlormequat negatively affected flowering characteristics and total nectar/spike in the winter.