The cucumber 'Euphorbia' was grown in a high-wire system at a density of 2.2 plants per square metre. All plants initially received supplementary lighting for 20 hours each day from 400W high-pressure sodium lamps mounted above the canopy.
Once the crop reached its final height, two lighting treatments were compared. One had overhead lighting as before but in the other, while 65 per cent of the supplementary lighting came from overhead lamps, 35 per cent came from 250W high-pressure sodium lamps mounted to one side of the crop.
The lamps, equipped with wide-spreading reflectors, were mounted vertically one metre above the ground. Although less light fell on the uppermost leaves, the side-lighting supplied more light to the lower leaves on that side of the canopy.
The rate of photosynthesis of all the leaves on the lit side of the plants was 40 per cent higher than on plants that were lit only from above. Air temperature around the fruits was also increased by side-lighting. Overall, the fruit yield from side-lighting was 11 per cent higher and the fruit elongated faster and were darker green.
Effects of Intracanopy Lighting on Photosynthetic Characteristics in Cucumber by Pettersen, Torre and Gislerod (2010). Scientia Horticulturae 125 (3): 77-81. The contents of issues of Scientia Horticulturae and abstracts of papers are provided at www.elsevier.com/locate/scihorti