Influence of light intensity and photoperiod on inflorescence initiation in tomatoes.

The tomato cultivars Eurocross BB and Ailsa Craig were propagated under two light intensities (6,455 and 12,910 lux) combined with two photoperiods (8 and 16 hours) at a temperature of 24?C and a CO2 concentration of 1,600 ppm. Rates of leaf production were linear and increased with increasing light integrals. In similar light integrals (103.3 kilolux-hours) rate of leaf production was almost similar, but inflorescence initiation occurred earlier and after fewer leaves in the shorter photoperiod. The higher light intensity signifi cantly reduced leaf number, but photoperiod had no significant effect on overall leaf number to the first inflorescence. It is suggested that the assimilate supply in the apex, which is dependent on light intensity and CO2 supply, may have been more influential than photoperiod on leaf number and stage of inflorescence initiation. The time to inflorescence initiation was reduced by 9.2 days in the higher light intensity and by 6.2 days in the longer photoperiod. Inflorescence initiation occurred earlier and after fewer leaves in Eurocross BB than in Ailsa Craig, and the former cultivar was less affected by changes in light conditions.