Antagonistic action of blue and red light on shoot elongation in petunia depends on gibberellin, but the effects on flowering are not generally linked to gibberellin

• Published in: Environmental and experimental botany Vol. 121; pp. 102 - 111
• Main Authors: Fukuda, Naoya, Ajima, Chiho, Yukawa, Tomohisa, Olsen, Jorunn E.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.01.2016
• Subjects: adverse effects; Blue light; buds; flowering; gibberellins; light intensity; Light quality; Petunia; plant morphology; Red light; Shoot elongation; Transition to floral development; uniconazole; Light quality; Red light; Shoot elongation; Blue light; Petunia; Transition to floral development
• ISSN: 0098-8472; 1873-7307
• DOI: 10.1016/j.envexpbot.2015.06.014

[Display omitted] Plant morphology and flowering are influenced by light quality, but responses vary between species. Here we investigated effects of irradiance (70 or 150μmolm−2s−1) of red (R) and blue (B) compared to white (W) light, provided by light emitting diodes, on growth and flowering in petunia. R light inhibited shoot elongation, but opposite to commonly observed, B light greatly enhanced shoot elongation. Consistent with this, bioactive gibberellins (GA1, GA4) showed higher and lower levels under B and R light, respectively, and GA3 application induced elongation in uniconazole-treated plants, although delayed in R. Inhibited shoot elongation under RB treatment in spite of higher GA level compared to R only, supports that R light inhibits elongation growth, and indicates negative effect of R light on GA signaling. Floral bud formation and flowering occurred earlier under B compared to W light. Whereas no floral buds were observed under low R irradiance, high R irradiance and temporal switching to B light during long-term low R irradiance induced floral development. Except slight trends of promoting effect of the highest GA3 level and delay in uniconazole-response under B light, lack of flowering under low R irradiance was not significantly affected by uniconazole or GA3 application. In conclusion, B and R light are strong signals enhancing and inhibiting shoot elongation, respectively, through modulation of GA content. B light is a strong signal in floral bud formation, whereas effect of R light depends on irradiance, indicating existence of an energy/photosynthesis-related floral pathway in petunia. Although light quality affects flowering and main shoot elongation, these responses do probably not correlate with each other through GA synthesis.