FAR-RED AT END OF DAY AND REDUCED IRRADIANCE AFFECT PLANT HEIGHT OF EASTER AND ASIATIC HYBRID LILIES

Potted bulbs of Lilium longiflorum Thunb. 'Ace' and 'Nellie White' and Lilium (Asiatic hybrid) 'Enchantment' were grown in a greenhouse unde r ambient photoperiod (APP), 8-h photoperiod by removing twilight from ambient by blackout cloth (8PP), or 8PP extended with 1 hour of low-i ntensity far-red radiation (9PP). Height of 'Ace','Nellie White', and 'Enchantment' increased by 24%, 18%, and 12%, respectively, under APP and by 118%, 100%, and 44%, respectively, under 9PP compared to 8PP. I n a second experiment, the effects of reduced irradiance (0%, 25%, 50% , and 75% shade) were determined on the same cultivars grown under APP or 8PP. The effects of APP on height were similar in magnitude for 'A ce' and 'Nellie White' but were insignificant for 'Enchantment' compar ed to 8PP. Shading increased height linearly for all cultivars. The re gression was greater under APP (2.8 mm/percent shade) than under 8PP ( 1.8 mm/percent shade) for 'Ace' and 'Nellie White' combined. Plant hei ght of 'Enchantnent' was less affected by reduced irradiance. For all cultivars, APP or 9PP produced higher stem dry weight compared to 8PP. Shading decreased leaf and bulb dry weight of the Easter lily cultiva rs.