Immediate and delayed effects of diurnal temperature drops on growth and reproductive development of tomato plants grown under continuous lighting

Abstract

Growing tomato plants (Lycopersicon esculentum Mill) under 24�h irradiation at constant temper� ature results in photoinhibition of the photosynthetic apparatus and lightinduced injury of leaves, which is manifested in interveinal chlorosis and has a negative effect on growth and development. At later stages of plant development, the unfavorable influence of continuous lighting (CL) applied during the prereproduc� tive period was evident in the delayed flowering, reduced fruit set and yield. In order to eliminate negative consequences of CL, the plants were exposed daily during the prereproductive period to temperature drops to 10°C for 2 h (DROP). Control plants were grown under 16�h photoperiod at 26/20°C (day/night) temper� ature. By the end of the prereproductive period (d ay 37), DROPtreated and control plants were trans� planted to a greenhouse and grown under identical conditions of natural photoperiod throughout the spring- summer season. The application of DROP under CL throughout the prereproductive period prevented the appearance of leaf chlorosis, enlarged leaf area, and increased the plant biomass. Furthermore, in DROP� treated plants, no adverse aftereffects of CL were observed in subsequent development. The DROPtreated plants did not differ from control plants in terms of time to flowering, the fruit set and total yield but were superior to control plants with regard to the early fruit yield. It is concluded that the DROPtreatment helps to employ the potential advantages of CL by mitigating its negative effects on plants.