Blue light advances bud burst in branches of three temperate deciduous tree species under short-day conditions

Abstract

During spring, utilising multiple cues allow temperate tree species 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 (400-500nm) 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 temperate deciduous tree species has not previously been reported. We tested the hypotheses that blue light would advance spring bud burst in temperate tree species, and that late-successional species would respond more than early-successional species, whos 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.\n\nKey MessageAn 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.