KEEPING QUALITY OF CUT ROSES AS AFFECTED BY HIGH SUPPLEMENTARY IRRADIATION

The rose cultivars 'Kiss', 'Frisco', 'Cardinal', 'Madelon' and 'Jaguar ' were grown in a greenhouse under four different levels of supplement ary irradiance (130, 190, 250 and 370 mumol m-2 s-1) applied for 20 h day-1. Five times during the production period roses were harvested fo r the purpose of testing the keeping quality. Vase life and number of days till occurrence of bent neck was about 30% higher when the roses were harvested in June than when they were harvested in November and J anuary. Vase life increased when the supplementary irradiance level in creased from 130 to 370 mumol m-2 s-1. The increase in vase life with increase in radiation was most pronounced for 'Cardinal' and 'Madelon' . Significant cultivar differences in vase life and days to leaf drop and bent neck were observed, 'Madelon' had the longest vase life.