Chromatic and numerical approaches for the monitoring of corn plants under moderate water stress

Abstract

The increasing scarcity of freshwater supplies, notably due to drought conditions elicited by climate changes, has a detrimental impact in the yield of crops worldwide. Not surprisingly, this type of abiotic stress factor has been the object of extensive studies in plant physiology, precision agriculture and remote sensing fields, just to name a few. Its effects on C 4 species like corn (Zea mays L., maize) tend to follow a cumulative pattern with distinct stages of severity. In its early, moderate, stage, it has a minor impact on the plants' chlorophyll contents. Nonetheless, it is essential to detect and manage it before irreversible damage to the plants' photosynthetic apparatus can occur. The unifacial corn leaves are equipped with stress adaptation mechanisms such as the rearrangement of their chloroplasts. Accordingly, their chromatic attributes can change under moderate water deficit conditions. These changes, however, are often subtle and their assessment can be impaired by varying illumination conditions. Alternatively, multispectral vegetation indices can be employed to assist the monitoring of these plants' water status. In this paper, we address these aspects. More specifically, we investigate the sensitivity of corn leaves' chromatic attributes to changes in their optical properties in response to moderate water stress. Furthermore, we propose an alternative index to assist the monitoring of these changes in the visible (photosynthetic) spectral domain. We carried out our investigation using a first-principles in silico experimental approach supported by measured data. Our findings are expected to contribute to the advance of the current understanding about moderate water stress related effects on C 4 plants. Such an understanding, in turn, is instrumental for the development of new water-stress monitoring technologies with a higher reliability to cost ratio.