HIGH R FR HPS-PULSES ENHANCE EARLINESS OF FLOWERING OF EXACUM (EXACUM-AFFINE BALF F) AND GERANIUM (PELARGONIUM X HORTORUM BAILEY,L.H.)/

Four consecutive crops (Fall 1988, Winter 1989, Summer 1989 and Fall 1 989) of exacum (Exacum affine Balf. f. 'Elfin') and geranium (Pelargon ium x hortorum L. H. Bailey 'Hollywood Star' and 'Hollywood Red') were grown in a greenhouse under three lighting treatments: ambient: 16-h high pressure sodium (HPS) lighting of 100 mumol m-2 s-1 between 0600 and 2200 h; and 16 h HPS-pulse lighting (45 s shut off, 90 s recharge) once every hour between 0600 and 2200 h. The growth index [(height x width)/2] of exacum plants was similar, regardless of the light treatm ent used. However the growth index of both geranium cultivars receivin g HPS-pulse lighting was significantly less than those receiving the t wo other treatments. Exacum top dry weight was 225 % greater under pul se lighting than under ambient light. During fall 1988, HPS-pulse ligh ting increased flower dry weight of Hollywood Red by 400% and 87% comp ared to ambient and HPS lighting, respectively.