|Authors: ||X. Guo, X. Hao, J.M. Zheng, C. Little, S. Khosla|
|Keywords: ||supplemental light, mini-cucumber, yield, fruit quality, year-round greenhouse|
High pressure sodium (HPS) lamps have traditionally been the main light source for supplemental lighting in greenhouse crop production because of high reliability and efficiency in producing photosynthetically active radiation (PAR). The light spectrum of HPS has reduced blue light in comparison to sunlight.
Therefore, plant growth and development could be benefited from an alternative light source with a spectrum similar to sunlight and containing more blue light, such as the recently developed plasma lamps.
Some growth chamber studies reveal that plant growth and development was indeed better under plasma light in comparison to HPS, when plasma light was used as the sole overhead light source.
Plant responses to plasma in greenhouse conditions could be different because the plant is also exposed to natural solar radiation.
Therefore, this study investigated the impacts of plasma light on greenhouse-grown mini cucumber (Cucumis sativus L. 'Picowell') growth, fruit yield and quality, in comparison to HPS light over two winter seasons (October 2012 to March 2013 and October 2014 to April 2015) in a 200-m2 greenhouse.
The greenhouse was divided into 4 sections (50 m2 in each section); two sections were fitted with plasma light while the other two sections had HPS (2 replications). Both lighting types provided the same amount of PAR (165 Ámol m-2 s-1). For both seasons, the total fruit yield was not affected by lamp type.
However, in the first season (October 2012 to March 2013), the cumulative marketable fruit yield under plasma was significantly greater than that under HPS light.
Due to the different impacts of light type on marketable fruit yield during the two winter season, future research should focus on the effect of solar radiation on choosing the proper light source in year-round greenhouse vegetable production with supplemental light.
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