The Quality and Quality Shifting of the Night Interruption Light Affect the Morphogenesis and Flowering in Floricultural Plants

Abstract

The effects of the quality of night interruption (NI) on the morphogenesis and flowering were investigated in Petunia hybrida Hort. “Easy Wave Pink” (qualitative long-day plant), Pelargonium hortorum L.H. Bailey “Ringo 2000 Violet” (day-neutral plant), and Dendranthema grandiflorum “gaya yellow” (qualitative short-day plant). Plants were grown in a closed-type plant factory under a light intensity of 180 μmol m-2 ·s-1 PPFD (photosynthetic photon flux density) provided by white (W) light-emitting diodes (LEDs) under a condition of either long day (LD, 16 h light/8 h dark), short day (SD, 10 h light/14 h dark), or SD with 4 h NI. NI was provided by 10 ± 3 μmol m-2 ·s-1 PPFD. In the first experiment, NI was provided by blue (NI-B), green (NI-G), red (NI-R), far-red (NI-Fr), or white (NI-W) LEDs. The shoot length and plant height of the petunia and the geranium were the greatest in NI-Fr, while those of the chrysanthemum were the greatest in LD. In the petunia, flowering was observed in LD, NI-G, NI-Fr, and NI-W. Flowering of the geranium was not affected by the night interruption light (NIL) quality, and all plants flowered in all treatments. Flowering of the chrysanthemum was observed in SD, NI-B, and NI-Fr. These results suggest that the morphogenesis, flowering, and transcriptional factors of these plants were highly affected by the quality of the NIL, especially in the chrysanthemum. Furthermore, NI-R or NI-W was the most suitable in the NI strategy of controlling the morphogenesis and flowering of the long-day plants during SD seasons.