TeraHertz Plant Imaging

TeraHertz Imaging consists in illuminating an object with a pulsed terahertz radiation and capturing the response through an array of sensors in the same spectral region.

In the THz region, a photon carries a very small energy when compared with the ionization energy of atoms, which is why it is a totally safe technology that poses no risk to biological organisms. In addition, the very long wavelength (a fraction of a millimeter) makes it possible to strongly limit scattering processes due to the presence of small particles in the sample.

In contrast, this radiation is strongly absorbed by some molecules and, in particular, by water. This is why it is an ideal technology for observing both dry objects and very thin objects. Plant leaves are elements that are very well observed in this region. 

This method makes it possible to monitor the amount of water in the leaves or major leaf districts, even on the same leaf as a function of time. This allows, for example, early detection of any signs of leaf water stress to enable precision irrigation. See for example: “Non-invasive absolute measurement of leaf water content using terahertz quantum cascade lasers”

In addition, the method is suitable, for example, to study the effect of the presence of ozone in the air on the plants or the interaction with hormones such as abscisic acid (ABA). 

Moreover, it has been used for the quality assessment of dry fruits like chestnuts and hazelnuts. See for example “Detection of fungal infections in chestnuts: a terahertz imaging-based approach“