Drought affects the water potential in the plant tissues. When water limitation reduces the water potential, many physiological processes become impaired and thus slow down or even stop. Monitoring water potential by non-invasive measures is an important tool for detecting stress induced by water limitation. NIR imaging can serve as indicator of reduced water potental as the NIR-color class correlates to the water potential of the tissue.
Imposing three classes of reduced irrigation to vines, the NIR response increased with lower water availability, proving that NIR imaging is applicable to monitor drought responses in perennial plants.

Briglia N, Nuzzo V, Petrozza A, Summerer S, Cellini F, Montanaro G (2019) Preliminary high-throughput phenotyping analysis in grapevines under drought. BIO Web Conf. 13:2003; https://www.bio-conferences.org/articles/bioconf/abs/2019/02/bioconf_conavi2018_02003/bioconf_conavi2018_02003.html