Leaf initiation rate is determined by more than just air temperature: considerations for greenhouse climate control and crop modeling

Plant growth and development are highly responsive to plant temperature. In greenhouses, plant temperatures are often not monitored and air temperature (T_air) is used as their approximation. However, even under controlled conditions the temperature of a plant may not always equal T_air. Leaf initiation in the shoot apical meristem is a critical process for plant development and growth. T_air is considered as the dominant environmental factor influencing the rate at which new leaves are initiated (LIR). Recent studies suggested that considering T_air as the only factor influencing LIR may not always be correct. The temperature of the shoot apical meristem (T_meristem) in cucumber and tomato plants was found to deviate from T_air by several degrees Celsius even under moderate conditions. This deviation was a function of other environmental factors, such as radiation, air humidity, wind speed, and plant traits that influence the heat budget of the shoot apical meristem. In addition, it was demonstrated that LIR is reduced by low light intensities at constant T_meristem in cucumber and tomato plants. This paper reviews these findings suggesting that LIR is determined by more than T_air and discusses considerations and their potential implications in greenhouse climate control and crop modeling.