Work

Monitoring leaf temperatures and environmental dynamics in propagation greenhouses

Year: 2025

Type: article

Abstract: CONTEXTLeaf temperature strongly influences water status, stress responses, and rooting success in unrooted cuttings. Commercial propagation greenhouses commonly employ “Artificial Leaf” thermistors positioned above mist emitters for mist irrigation scheduling, but these sensors may not accurately reflect leaf cooling under misting. Contact sensors such as thermocouples provide accurate readings but are impractical in commercial operations due to labor and handling challenges. Non-contact infrared (IR) radiometers offer a potential alternative, but their performance under propagation conditions has not been validated.OBJECTIVEThis study evaluated the accuracy of different leaf temperature measurement methods for unrooted cuttings, with a particular focus on validating IR radiometers and Artificial Leaf thermistors against thermocouples. A second objective was to characterize environmental factors affecting leaf–air temperature differences (LAD) in both research and commercial propagation greenhouses.METHODSComparisons of sensor performance were conducted in a University of Florida greenhouse with Chrysanthemum ×grandiflorum cuttings. Five sensor types were tested: thermocouples, fine-wire thermistors, IR radiometers (from Apogee and Omega), and an Artificial Leaf thermistor. Data were logged at 1-min intervals over seven days and analyzed with linear mixed models. Complementary trials in seven U.S. commercial propagation greenhouses deployed IR radiometers to monitor leaf temperature in relation to air temperature, relative humidity, radiation, and mist scheduling methods.RESULTS AND CONCLUSIONSIn the research greenhouse, all sensors agreed during nighttime, but the Artificial Leaf thermistor overestimated daytime leaf temperature by 2.2–11.2 °C compared with thermocouples. Both IR radiometers closely tracked thermocouple measurements across diurnal cycles, with lower residual variance than the Artificial Leaf. Leaf temperature dropped immediately following mist events, confirming rapid evaporative cooling. Commercial greenhouse data showed LAD values ranging from -1.6 to +3.2 °C, with the most positive LAD observed in facilities using high-pressure sodium (HPS) lighting. These findings demonstrate that IR radiometers provide accurate, non-invasive monitoring of leaf temperature under propagation conditions, whereas Artificial Leaf thermistors substantially overestimate leaf heating.SIGNIFICANCEAccurate, real-time monitoring of leaf temperature is critical for optimizing mist irrigation, water-use efficiency, and cutting quality in propagation systems. This study supports the replacement of Artificial Leaf thermistors with IR radiometers in commercial greenhouses. Adoption of non-contact IR sensing enables dynamic mist control based on actual leaf conditions, reducing water waste and mitigating stress in unrooted cuttings.

Source: Smart Agricultural Technology

DOI: 10.1016/j.atech.2025.101638

Authors: Daniel Crawford, Ying Zhang, Paul Fisher

Institution: University of Florida

Language: English

Topic: Greenhouse Technology and Climate Control

Subfield: Plant Science

Field: Agricultural and Biological Sciences

Domain: Life Sciences

SDG: Zero hunger

Open Access status: gold

Estimated APC paid: $1,770