Influence of electrical signals on pea leaf reflectance in the 400-800-nm range

Local action of stressors induces generation and propagation of electrical signals (ESs), which influence numerous physiological processes (including photosynthesis, expression of genes, production of phytohormones, etc.) in undamaged parts of plants; i.e. they induce a systemic stress response. Development of methods of remote sensing of this response (in particular, optical methods) is an important practical task for agricultural and ecological monitoring. However, this problem is not sufficiently researched. Earlier, we reported that ESs influence the photochemical reflectance index, which can be calculated on the basis of reflected light at 531 and 570 nm, and these changes are connected with photosynthetic changes. The aim of the current work is investigation of the influence of ESs on reflectance at broad spectral bands (400-500 nm, 500-600 nm, 600-700 nm and 700-800 nm). We showed that burning-induced ESs caused transient increase of intensity of reflected light at the all investigated spectral bands of visible light: reflectance at 600-700 nm had the maximal magnitude of changes and reflectance at 700-800 nm had the minimal magnitude of changes. Dynamics of the reflectance changes were distinguished from dynamics of photosynthetic changes, induced by ESs; i.e. ESs-induced changes in reflectance seem to be weakly connected with the photosynthetic response. Thus, our results show that changes in reflectance at broad spectral bands can also be used for remote sensing of the ESs-induced systemic stress response in plants.