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

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 degrees 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 degrees 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.