Supplemental far-red light influences flowering traits and interactions with a pollinator in tomato crops

Plants sense a reduction in the red to far-red light ratio as a cue of light competition and respond by accelerated growth and reproduction. These responses can be exploited in horticulture by applying far-red light-emitting diodes (LEDs). Responses to far-red light also have marked effects on plant defences and influence plant-herbivore and plant-carnivore interactions. It is, however, not known how changes in flowering traits induced by far-red light affect plant-pollinator interactions. We studied the effects of supplemental far-red light on tomato truss development, floral volatiles, pollen sugar and amino acid content, and the foraging behaviour of the buff-tailed bumblebee (Bombus terrestris).Far-red light significantly increased plant height, accelerated flowering and increased the number of flowers per truss. Floral volatile emission was increased in the early stages of tomato development, and sugar content was higher in pollen of plants exposed to far-red light. Pollen amino acid content was not affected. Bumblebees spent more time foraging on far-red-exposed plants and visited more flowers on these plants.We conclude that plant exposure to far-red light leads to changes in flower traits that increase the attraction of bumblebees, which has promising implications for the use of supplemental far-red LEDs in greenhouse tomato crops.