Non-contacting techniques for plant drought stress detection

Plant drought stress indicators such as crop water stress index (CWSI), plant motion in the form of covariance of top-projected canopy area (COV_TPCA), leaf water content represented as equivalent water thickness (EWT), and their threshold values for drought stress detection were established from measurements. Performances of these indicators in detecting drought stress of New Guinea Impatiens plants in a controlled environment were evaluated. Analysis of variance (ANOVA) was conducted to compare the timing of drought stress detection by these indicators against the timing of incipient drought stress defined by evapotranspiration (ET) and timing of human visual detection. Statistical analysis was also performed to study the consistency of the threshold values of the indicators in different experiments. ANOVA results showed that the CWSI was the most reliable indicator for early plant drought stress detection. The timing of the drought stress detection from the earliest to the latest was CWSI, EWT and COV_TPCA. While COV_TPCA and EWT were not able to detect drought stress as early as CWSI, ANOVA results indicated that these two indicators were able to detect drought stress no later than visual detection. ANOVA results also showed that there was no significant difference in threshold values of CWSI and COV_TPCA in different experiments, but different cultivars used in the experiments resulted in significant differences in EWT threshold values