Reduction of visible chilling injury in sweet basil (Ocimum basilicum L.) using artificial illumination

The production of sweet basil (Ocimum basilicum L.) in Israel during the winter exposes the crop to temperatures below 12 degrees C, which promote visible chilling injuries, reducing yields by up to 85%. In 2011, the addition of illumination was examined as an agro-technique to mitigate visible chilling injuries under a semi-commercial operation. Lamps were maintained at 30100 cm above plants' tops, and agronomical, morphological and physiological parameters were evaluated. Artificial illumination increased the mean and minimum temperatures between 7.1 and 1.1 degrees C, and 2.4 and 2.2 degrees C compared to out-door or non-illuminated tunnels, respectively. Leaf temperatures were increased by 35 degrees C. Illuminated plants yielded more (P < 0.05) than non-illuminated plants, regardless of lamp height. Highest (P < 0.05) yields were recorded when lamps were situated 4090 cm above plants' tops. The effect of illumination on yield was related to increased leaf area and internodes length. Morning dew was reduced by 85% in plants subjected to artificial illumination; and visible chilling injuries were alleviated by 8085%, regardless of lamp height. The results indicate that increased leaf and air temperature is likely the fundamental chilling injury mitigating factor. Interestingly, leakage of soluble and accumulation of antioxidant, phenols and rosmarinic acid was similar in illuminated and non-illuminated plants. This discrepancy between the horticultural and the physiological parameters should be studied further, as artificial illumination might have additional mechanisms affecting chilling injury other than direct temperature increase. (C) 2016 Elsevier GmbH. All rights reserved.