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Temperature Drop Improved Responses of Greenhouse Sweet Peppers to Long Photoperiod of Supplemental Lighting

Hao, X.M., Y. Zhang, X. Guo, C. Little and J. Zheng and S. Khosla (2016) “Temperature Drop Improved Responses of Greenhouse Sweet Peppers to Long Photoperiod of Supplemental Lighting", 2016 Annual Conference of American Society of Horticultural Science, Atlanta, Georgia, USA, Aug. 7-11, 2016, Oral Presentation. (Abstract).

Abstract

It is well known that long photoperiods of supplemental lighting cause photo-injury such as leaf chlorosis and necrotic spotting in greenhouse sweet peppers. This photo-injury has limited the application of long photoperiod of supplemental lighting and the yield increase by supplemental lighting, in year-round greenhouse sweet pepper production. In our previous study, we have found that dynamic temperature integration (TI) with temperature drop can improve the response of greenhouse tomatoes to long photoperiod of supplemental lighting because it promoted the translocation of photo-assimilates from leaf to fruit. This promotion of photo-assimilate translocation could also has the potential to help sweet pepper plants to reduce the photo-injury and improve the response to long photoperiods of supplemental lighting. Therefore, we conducted this study with the aim to investigate the interactions between photoperiods and temperature control strategies for improving the response of sweet peppers to long photoperiods of supplemental lighting. The study was conducted from Oct. 2015 to Feb. 2016 in 8 greenhouse compartments, each with 50 m2 of growing area. Two photoperiods (17h - Control and 21 h – Long Photoperiod) and two temperature integration strategies (Control TI – no temperature drop and Dynamic TI with temperature drop to 15.5 oC for 3 h at the end of photoperiod) were applied in the 8 compartments (2 complete replications). Dynamic TI with temperature drop had the same 24-h average temperature as Control TI; the low temperature during the drop period was compensated with higher temperature in other periods over a day (24-h period). Dynamic TI with temperature drop significantly reduced photo-injury and increased fruit yield at the long photoperiod (21 h). Therefore, dynamic temperature integration with temperature drop can be used for improving the response of greenhouse sweet peppers to long photoperiods of supplemental lighting in year-round production.

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