Stress detection in vegetation based on remotely sensed light absorption coefficient

ABSTRACT

Environmental stresses on plants are among the major limitations to crop productivity. Plants are naturally equipped with a set of acclimatory mechanisms enabling them to withstand stresses without irreversible damage. Here, we overhauled the approach to non-invasive gauging of the response of maize to combined drought and high-light stresses. This was done to leverage the advantages of a recently developed framework based on using the reflected signal absorption coefficient modality. We document the deployment of two responses, one based on non-photochemical quenching (NPQ) of the absorbed light energy and the second on the adjustment of leaf photosynthetically active radiation (PAR) interception. The NPQ-based response, implemented by the xanthophyll cycle and inferred from changes in the reflection of light in the blue-green region of the spectrum, engaged at the beginning of the stress but quickly reached a plateau. We demonstrate that altering leaf absorption in PAR is a fundamental plant response mechanism to diverse stresses. This response is quantified by the PAR absorption coefficient retrieved from the non-destructively measured reflectance. A profound decrease in the PAR absorption coefficient in the whole PAR region was shown to be a reliable measure of the degree of stress regardless of its cause. The effects of superficial shading and leaf position were readily detectable by the leaf PAR absorption coefficient. We consider this report a proof of concept for quantifying plant stress and monitoring the acclimation state via the absorption coefficient in the PAR region through non-destructive, remotely sensed techniques.

KEYWORDS:

• absorption coefficient
• PAR interception
• non-photochemical quenching
• relative water content
• volumetric water content

Acknowledgements

The collection of data used in the paper was partially supported in 2007–2011 by the Center for Advanced Land Management and Information Technologies at the University of Nebraska-Lincoln, the Nebraska Agricultural Experiment Station with funding from the Hatch Act [Accession Number 1002649] through the USDA National Institute of Food and Agriculture. We thank Mr Mark Mesarch and Mr Dave Scoby for their help in the original greenhouse studies (including setting up equipment, taking and analysing data, and providing important critiques and suggestions).

Disclosure statement

No potential conflict of interest was reported by the author(s).