Plant temperature-based indices using infrared thermography for detecting water status in sesame under greenhouse conditions

Abstract There have been studies on the effect of water stresses on leaf stomatal conductance (g s ); however, the scientific reports on using non-contact techniques such as thermography for sesame ( Sesamum indicum L.) are rare. The objectives of this study were hence to detect water status in sesame (genotype, “Naz-Takshakhe”) under greenhouse conditions using Crop Water Stress (CWSI) and stomatal conductance (I g ) Indices. One hundred and fifty pots were randomly assigned to three equal groups which were irrigated at soil water potential of −0.1 MPa (well-watered, WW), −1.0 MPa (moderate-water stressed, MWS), and −1.5 MPa (severe-water stressed, SWS). Four formulations of CWSI and two of Ig using canopy temperature (T C ) from the WW treatment or temperature from a wet reference for the upper threshold and T C from the SWS treatment, temperature from a dry reference or air temperature plus 3° as the lower threshold were compared. Moreover, an additional CWSI and Ig formulations were also obtained by non-water stress baseline (NWSB) information using meteorological data. Furthermore, the relative water content (RWC) and g s were measured on the youngest and uppermost fully developed leaves of each pot. T C of MWS and SWS plants was higher than WW plants by 1.9 and 2.6 °C, respectively. A significant and linear relationship ( P   0.001) between CWSI/I g and g s /RWC was found. Therefore, both physiological traits of g s and RWC can be estimated by temperature-based indices of CWSI/I g . The results also showed the developed system enables us to estimate actual time variations in canopy temperatures. This study validates the effectiveness of using CWSI/I g for non-destructive detection of water stress and estimation of relative water content in sesame.