Comparison of Physical and System Factors Impacting Hydration Sensing in Leaves Using Terahertz Time-Domain and Quantum Cascade Laser Feedback Interferometry Imaging

To reduce the water footprint in agriculture, the recent push toward precision irrigation management has initiated a sharp rise in photonics-based hydration sensing in plants in a non-contact, non-invasive manner. Here, this aspect of sensing was employed in the terahertz (THz) range for mapping liquid water in the plucked leaves of Bambusa vulgaris and Celtis sinensis. Two complementary techniques, broadband THz time-domain spectroscopic imaging and THz quantum cascade laser-based imaging, were utilized. The resulting hydration maps capture the spatial variations within the leaves as well as the hydration dynamics in various time scales. Although both techniques employed raster scanning to acquire the THz image, the results provide very distinct and different information. Terahertz time-domain spectroscopy provides rich spectral and phase information detailing the dehydration effects on the leaf structure, while THz quantum cascade laser-based laser feedback interferometry gives insight into the fast dynamic variation in dehydration patterns.

Automated summary

In order to reduce water consumption in agriculture, photonics-based hydration sensing technology has been widely used for non-contact, non-invasive mapping of liquid water in plants. In this study, terahertz (THz) range sensing techniques were employed to map liquid water in leaves of Bambusa vulgaris and Celtis sinensis. Two complementary techniques, THz time-domain spectroscopic imaging and THz quantum cascade laser-based imaging, were utilized. The results provide detailed spatial and temporal information about hydration dynamics and dehydration effects on leaf structure.