Irrigation at the level of evapotranspiration aids growth recovery and photosynthesis rate in tomato grown under chilling stress

Although irrigation and temperature are predominant factors in tomato productivity in greenhouses, there is a lack of information on how these factors interact. Here, we examined single-factor responses and the interaction of three levels of irrigation (80, 100 and 120% of evapotranspiration) and two temperatures (normal temperature range of 13–30 °C and chilling temperature range of 4–24 °C) on growth, gas exchange, and antioxidant metabolism in relation to water uptake of pot-grown tomato plants ( Solanum lycopersicum L. ‘No. 1 Jinpeng’). Lower growth was observed with the 80 and 120% irrigation levels than with the 100% treatment. Our results suggest that irrigation at 100% of evapotranspiration is the optimal level for ameliorating the chilling sensitivity of tomato, because this level of irrigation may enhance relative water content as well as nitrogen content to maintain the photosynthesis rate and reduce the damage to cells by reactive oxygen species (ROS). The adverse effects of 80 and 120% levels of irrigation might be attributable to a decreased photosynthesis rate and increased ROS accumulation, which would result in increased cell damage. Therefore, the use of irrigation at 100% of evapotranspiration is the best choice to support the acclimatization of tomato seedlings to chilling temperatures.