Identification of Chlorophyll Fluorescence Parameters for Evaluating Drought Stress in Garden Plants

Background and objective: This study aimed to analyze chlorophyll fluorescence responses to drought stress in ten gardenplant species and to identify effective parameters for evaluating drought stress. Methods: The study took place from July to August 2023 in a greenhouse at Hankyong National University in Anseong,Gyeonggi-do, South Korea, to evaluate drought stress responses in ten garden plant species. After growing the plantsunder well-watered conditions under a drip irrigation system for 20 days, irrigation was withheld to induce drought stress. Chlorophyll fluorescence responses were measured at five-day intervals to define different drought stages. Results: During the control period, the plants exhibited the highest maximum chlorophyll fluorescence, indicating efficientelectron transport from PSII to PSI. However, maximum fluorescence decreased progressively following drought stresstreatment. To identify key photophysiological indicators for evaluating drought stress in garden plants, species-specificJIP-test parameters were calculated and analyzed using Pearson’s correlation analysis with soil moisture content. Parameters reflecting energy flux per leaf area showed significant positive correlations across all species. Based on thesecorrelations, a principal component analysis (PCA) was performed, which suggested that 11 parameters were associatedwith drought stress. To assess the importance of each variable, a multiple linear regression model was constructed. Themodel showed high predictive reliability, although some multicollinearity among independent variables was observed. After excluding mutual influences and evaluating the relative contributions of each variable, five chlorophyll fluorescenceparameters—TRo/CS, ABS/CS, RC/CS, ET2o/CS, and RE1o/CS—were proposed as effective indicators for assessingdrought stress in garden plants. Conclusion: The five chlorophyll fluorescence parameters—TRo/CS, ABS/CS, RC/CS, ET2o/CS, and RE1o/CS—proposed inthis study demonstrated the potential to serve as universally applicable indicators for assessing drought stress acrossvarious garden plant species. Their practical utility as evaluation metrics could be further strengthened through futurestudies incorporating species-specific sensitivity analyses or different planting conditions.