EFFECTS OF LIGHT QUALITY UNDER RED AND BLUE LIGHT EMITTING DIODES ON GROWTH AND EXPRESSION OF FBP28 IN PETUNIA

Abstract

Floral induction in Arabidopsis is influenced by blue and red light. In this study, we investigated the effects of light quality from different types of light emitting diodes (LED) on growth and floral induction in petunia (Petunia hybrida Vilm.) ‘Baccarat blue’, as well as the expression of the SOC1-like gene FBP28. Petunia plants with five true leaves were exposed to fluorescent lamps, red or blue LED after transplanting to a growth cabinet. The photoperiod was 14 h and the irradiance was adjusted to 100 µmol·m -2 ·s -1 (PPF) around the shoot apices. At the 53 rd day after, petunia plants under red LED showed lower plant height than the other treatments. The number of leaves and length of lateral shoots increased under red LED, and the shoot length became about 60% higher than under the blue LED treatment. However, flower bud initiation was inhibited under red LED treatment, and floral bud formation was then not observed at the end of experiment. The expression of the SOC1-like gene FBP28 in petunia was changed by light quality. Under white fluorescent light and blue LED light the transcript levels of FBP28 showed a diurnal rhythm. The transcript levels increased during the morning, and remained high during the lighting period. On the other hand, the expression of FBP28 was lower under red LED treatment during the lighting period. In Arabidopsis, the expression of SOC1, which is one of the key genes in floral induction, is stimulated by a signal from cryptochrome blue light receptors. In petunia, blue LED light as well as the blue part of the spectrum in white fluorescent light, can also induce FBP28 and floral induction, probably by a signal from cryptochrome-like photoreceptors.