Noy-Porat, T., Institute of Plant Sciences, Agricultural Research Organization, Bet-Dagan 50250, Israel, Department of Molecular Biology and Ecology of Plants, Tel Aviv University, Tel Aviv 69978, Israel
Cohen, D., Institute of Plant Sciences, Agricultural Research Organization, Bet-Dagan 50250, Israel
Mathew, D., Present address: Centre for Plant Biotechnology and Molecular Biology, College of Horticulture, Kerala Agricultural University, KAU, 680656, India
Eshel, A., Department of Molecular Biology and Ecology of Plants, Tel Aviv University, Tel Aviv 69978, Israel
Kamenetsky, R., Institute of Plant Sciences, Agricultural Research Organization, Bet-Dagan 50250, Israel
Flaishman, M.A., Institute of Plant Sciences, Agricultural Research Organization, Bet-Dagan 50250, Israel

In Narcissus tazetta, a monocotyledonous bulbous geophyte, floral initiation and differentiation occur within the bulb during the quiescent period in summer, when ambient temperatures are relatively high and the bulb is located underground with no foliage or roots. In many plant species, FLOWERING LOCUS T (FT) and its homologues are considered powerful promoters of flowering. The Narcissus FT gene homologue (NtFT) was isolated, and organ-specific expression patterns of NtFT during the annual cycle and reproductive development under different temperature regimes ere analysed using quantitative reverse transcription-PCR (qRT-PCR) and RNA in situ hybridization. During floral induction, NtFT was not expressed in bulb scales, roots, or foliage leaves, but it was detected inside the bulb in the apical meristem and leaf primordia. The expression of another key flowering gene, NLF, the LEAFY homologue in N. tazetta, was also observed only in meristem and leaf primordia within the bulbs; however, its expression id not coincide with that of NtFT during meristem transition to reproductive stage. Under high temperatures (25-30 °C) in the dark, NtFT expression occurred simultaneously with floral induction timing, indicating that floral induction is affected by high temperatures but not by photoperiod or vernalization. Monitoring the apical meristem of Narcissus in February-August of two growing seasons under ambient and controlled storage conditions showed that transition to flowering is temperature dependent and varies between years. Lack of NtFT and NLF expression in foliage leaves suggests that flower initiation control in Narcissus differs from that in common model plants. © The Author [2013].