Light sum, nitrogen level and growth retardant effects on flower and nectar production in Stachytarpheta frantzii

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Thomas-Granger, Karrie
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University of Guelph

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.

light sum, nitrogen, plant growth retardants, flower production, nectar production, Stachytarpheta franatii Polak.