SUPPLEMENTAL LIGHT QUALITY AFFECTS BUDBREAK, YIELD, AND VASE LIFE OF CUT ROSES

Rosa xhybrida 'Samantha' plants were grown under high-pressure sodium (HPS) lamps, HPS lamps fitted with blue gel filters to reduce the red to far-red (R : FR) ratio, or metal halide lamps. R : FR ratios were 1 :0.95, 1:2, and 1:0.26 for HPS, filtered HPS, and metal halide, respec tively. Although the R : FR ratio for metal halide was 3.5 times highe r than for HPS, the total energy from 630 to 750 nm was 2.8 times lowe r. At a nighttime supplemental photosynthetic photon flux of 70 to 75 mumol.m-2.s-1, plants under HPS and metal halide lamps produced 49% an d 64% more flowering shoots, respectively, than those under filtered H PS (averaged over two crop cycles). The quality index for flowers unde r HPS, metal halide, and filtered HPS was 25.0, 23.3, and 18.5, respec tively. Vase life was 10 to 11 days, regardless of treatment.