In: Phyton, 52 Fasc. 1 (2012), S. 163-175

Key words: Petunia × hybrida, light quality, date to flowering photosynthetically active radiation (PAR).

Summary

ILIAS I. F. & RAJAPAKSE N. 2012. Growth and flowering responses of Petunia × hybrida to different photoperiods, light qualities and temperatures. Does light quality affect photosynthetic apparatus of petunia? – Phyton (Horn, Austria) 52 (1): 163–175.

Factorial combinations of two photoperiods (10 and 14 hd–1), two day temperatures (20 and 26 ºC) and two light qualities Red (R) and Far red (FR) were imposed on growth, flowering develop-ment and chlorophyll fluorescence of Petunia × hybrida VILM. plants grown for 6 weeks in growth chambers. 14 hd–1 photoperiod decreased the day to flowering by 8 d while the days to flower (DF) were on average 3.1 longer under R light compared to FR light. Light intensity was on average 5.38 higher under R light compared to FR light. Stem dry weight was on average 0.17 g higher when temperature was 20 ºC as compared to 26 ºC. Leaf dry weight can effect by temperature and light quality while the interaction between them can affect the number of lateral shoots and the number of unflowering buds. Light quality can affect the number of flowers. The differences in flowering, height and weight observed for petunia suggest that they may be useful sources of variability for petunia breeding programs. Additionally temperature and photoperiod under FR light quality didn‘t affect the chlorophyll fluorescence parameters while under R light the maximum quantum yield (Fv/Fm) decreased significantly.