GROWTH AND DRY-WEIGHT DISTRIBUTION IN CALLISTEPHUS CHINENSIS AS INFLUENCED BY LIGHTING TREATMENT

Plants of two cultivars of Callistephus chinensis (Queen of the Market and Johannistag) were grown in 8 h of daylight per day with one of the following treatments given during the 16 h dark period: (a) darkness-'uninterrupted night', (b) I h of light in the middle of the dark period-a 'night break', (c) I min of light in every hour of the dark period-'cyclic lighting', (d) light throughout-'continuous light'.The plants receiving uninterrupted dark periods remained compact and rosetted in habit with small leaves, while leaf expansion, stem extension, and flower initiation were promoted in all three illumination treatments (b, c, d). Although these three treatments produced similar increases in leaf area, continuous light was the most effective for the promotion of both stem growth and flower initiation while cyclic lighting was generally more effective than a I-h night break.Continuous light also caused more dry matter to be diverted to stems at any given vegetative dry weight and it was shown that the stem weight ratio of both varieties was correlated with stem length. © 1969 OXFORD UNIVERSITY PRESS.