Water is essential to the health of plants, with water abundance in plant leaves a sign of leaf vigor. Fortunately, several Chinese researchers have pooled their findings on terahertz spectroscopy to develop an approach for estimating the water status of plant leaves by terahertz-frequency time-domain spectroscopy. Their studies show the effects of drying on the water distribution within the leaves of different types of plants. They also reveal how terahertz spectroscopy systems might be used for practically monitoring the temporal and spatial variations of water flow in different types of wintersweet, ginkgo, and bamboo plant leaves
Imaging was performed at fixed frequencies of 0.60, 0.89, and 1.15 THz over time to show the changes in water distribution in, for example, a wintersweet leaf over four days. As the researchers discovered, the optimum THz imaging frequencies changed over time and with the dehydration of each plant leaf; different imaging frequencies showed different results for each type of plant leaf.
The differences stem from the variations in the compositions of the plant leaves (different compositions and leaf coatings). The researchers plan to explore the use of photoacoustic imaging in conjunction with THz imaging to better understand the distribution of water in different dehydrating plant leaves.
See “Temporal and Spatial Variability of Water Status in Plant Leaves by Terahertz Imaging,” IEEE Transactions on Terahertz Science and Technology, Vol. 8, No. 5, September 2018, pp. 520-527.