Dynamic temperature integration with temperature drop improved the response of greenhouse tomato to long photoperiod of supplemental lighting

Abstract

It is well known that long photoperiods (GROTERDAN17 h) of supplemental lighting cause photo-injury such as leaf chlorosis and necrotic spotting in greenhouse tomatoes. This photo-injury has limited the application of long photoperiod and the yield increase by supplemental lighting in year-round greenhouse tomato production. In our previous study, we have found that dynamic temperature integration (TI) with temperature drop can improve early fruit yield in tomato production because it promoted the translocation of photo-assimilates from leaf to fruit. This promotion of photo-assimilate translocation has the potential to help tomato 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 dynamic TI with temperature drop for improving the response of tomatoes to long photoperiods of supplemental lighting. The study was conducted from Oct. 2013 to Mar. 2014 in 8 greenhouse compartments, each with 50 m2 of growing area. Two photoperiods (17 h-control and 20 h-long photoperiod) and two temperature integration (TI) strategies (Control TI-no temperature drop and Dynamic TI with temperature drop to 13.5°C for 3 h at the end of photoperiod) were applied in the 8 compartments (2 complete replications). The dynamic TI had the same 24-h average temperature as the control TI; the low temperature during the drop period was compensated with higher temperature in other periods over a day (24-h period). The dynamic TI significantly reduced photo-injury and increased fruit yield and size at the long photoperiod (20-h). Therefore, dynamic temperature integration regime with a temperature drop can be used to improve the response of greenhouse tomatoes to long photoperiods of supplemental lighting in year-round production.