Blue light advances bud burst in branches of three deciduous tree species under short-day conditions
An LED spectrum containing blue light advanced bud burst in branches of Betula pendula, Alnus glutinosa and Quercus robur compared with a spectrum without blue light in a controlled environment.
During spring, utilising multiple cues allow tree species from temperate and boreal regions to coordinate their bud burst and leaf out, at the right moment to capitalise on favourable conditions for photosynthesis. Whilst the effect of blue light (400–500 nm) has been shown to increase percentage bud burst of axillary shoots of Rosa sp., the effects of blue light on spring-time bud burst of deciduous tree species have not previously been reported. We tested the hypotheses that blue light would advance spring bud burst in tree species, and that late-successional species would respond more than early-successional species, whose bud burst is primarily determined by temperature. The bud development of Alnus glutinosa, Betula pendula, and Quercus robur branches, cut from dormant trees, was monitored under two light treatments of equal photosynthetically active radiation (PAR, 400–700 nm) and temperature, either with or without blue light, under controlled environmental conditions. In the presence of blue light, the mean time required to reach 50% bud burst was reduced by 3.3 days in Betula pendula, 6 days in Alnus glutinosa, and 6.3 days in Quercus robur. This result highlights the potential of the blue region of the solar spectrum to be used as an extra cue that could help plants to regulate their spring phenology, alongside photoperiod and temperature. Understanding how plants combine photoreceptor-mediated cues with other environmental cues such as temperature to control phenology is essential if we are to accurately predict how tree species might respond to climate change.
KeywordsPhenology Bud break Leaf flush Spectral composition Spectral quality Photoreceptors
Our acknowledgments to Lammi Biological station staff, in particular, John Loehr, to Mikko Peltoniemi and the EU Life + MONIMET phenology camera network, to Viikki Greenhouses Facility at the University of Helsinki and Viikki Arboretum, Marta Pieristè, Marieke Trasser and Ulla Riihimäki for help sampling, Titta Kotilainen for processing the spectral irradiance measurements. Thanks to Otmar Urban, Line Nybakken, and the two anonymous reviewers for giving constructive comments which improved the manuscript.
CCB conceived, designed and carried out the experiment and statistical analyses. TMR supervised the design, analyses and interpretation of results. Both authors wrote the manuscript.
We thank the Finnish Academy of Science for funding the project through the funding decisions # 266523 and #304519 to TMR, and Valoya Ltd. for providing the LED Lamps.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no competing interests.
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