Potential of infrared radiation-thermography for screening salt-tolerant 'Pokkali' rice seedlings

Chonticha Phromduang1, Nantawan Kanawapee2, Piyada Theerakulpisut1, and Watanachai Lontom1*
Screening for salt-tolerance plants has been carried out to enhance yield production. Consequently, the physiological and growth parameters were performed. These methods are labor-intensive and destructive. Nowadays, non-destructive thermography has been used for detecting infrared radiation under water stress. However, monitoring progressive leaf temperature under salt stress conditions has rarely been reported in rice (Oryza sativa L.) This study aims to monitor salt stress response in 'Pokkali' rice seedlings using infrared radiation (IR) thermography together with physiological and growth parameters. Twenty-six-day-old 'Pokkali'rice seedlings, standard salt tolerant, were subjected to 80, 120, and 160 mM NaCl for 8 d under hydroponic conditions. Our study found that NaCl condition influences the emission of infrared radiation and the elevation in leaf temperature. Notably, seedlings exposed to 160 mM NaCl after 8 d exhibited significantly higher temperature changes (5.21 °C), and higher crop water stress index (CWSI). Likewise, we observed lower reductions in transpiration rate (88.19%), stomatal conductance (92.78%), and photosynthetic rate (70.99%). Together, the correlation matrix revealed a strong relationship between CWSI and leaf gas exchange parameters, including photosynthetic rate, transpiration rate, and stomatal conductance. Additionally, IR-thermal indices and some physiological parameters contributed to the segregation between control and salt stress groups. Therefore, the simple thermal imaging technique can effectively monitor salt stress responses at various NaCl concentrations in the 'Pokkali' rice. The application of IR-thermography will be applied to various abiotic stressors and different rice cultivars in the future.
Keywords: Oryza sativa, ?Pokkali? rice, salt stress, salt tolerance, screening, thermal imaging.
1Khon Kaen University, Faculty of Science, Department of Biology, Khon Kaen 40002, Thailand.
2Nakhon Phanom University, Faculty of Science, Nakhon Phanom 48000, Thailand.
*Corresponding author (watalo@kku.ac.th).