Comparative Analysis of the Environmental, Sap Flow, and Growth Characteristics of Paprika in Positive-Pressure and Non-Pressurized Semi-Closed Greenhouses

This study compared the internal environment, growth characteristics, and sap flow of paprika (Capsicum annuum L.) grown in a positive-pressure semi-closed greenhouse (PP-SCG) and a nonpressurized semi-closed greenhouse (NP-SCG) to analyze differences in growth and productivity according to the greenhouse structure.Data collected from two greenhouses in Gangjin-gun, Jeollanam-do, between August 1 and September 4, 2024, showed that the PP-SCG maintained a narrower diurnal temperature range and a more stable average temperature than the NP-SCG.While the relative humidity in the NP-SCG exceeded 80% throughout the study period, the PP-SCG recorded many days a relative humidity rate below this threshold.Sap flow was consistently higher in the PP-SCG, correlating with superior growth and yield outcomes.A multiple linear regression analysis revealed that in both greenhouses, a 1C increase in the internal temperature increased the sap flow by 0.043 mms -1 , whereas a 1% increase in RH reduced the sap flow by 0.039 mms -1 in the PP-SCG and by 0.018 mms -1 in the NP-SCG.These findings suggest that sap flow is a reliable real-time indicator of crop physiological responses, extending beyond its traditional role as a measure of water movement.NP-SCG control systems primarily focus on external factors such as light, temperature, and humidity.Integrating sap flow sensors to monitor internal water transport and physiological activity could enable more precise crop diagnostics and rapid environmental adjustments.Such an integrated control strategy is expected to enhance smart-farm management systems by enabling decisions based on actual crop responses rather than solely on external conditions.