Optical indicators of plant physiological activity

• Main Authors: Daniel Kováč, Alexander Ač, Ladislav Šigut, Karel Klem, Otmar Urban
• Format: Article
• Language: English
• Published: Mendel University Press 2012-01-01
• Series: Acta Universitatis Agriculturae et Silviculturae Mendelianae Brunensis
• Subjects: <i>Picea abies</i>; reflectance; vegetation indices; photosynthesis; ecophysiology
• Online Access: https://acta.mendelu.cz/60/3/0101/

Retrieving information on the plant physiological status from spectral reflectance is a challenging task in many ways. The easiest way to get the information is through normalized vegetation indices, that are based on a normalization of reflectance in specific wavebands. Beside the most common spectral indices such as Photochemical Reflectance Index PRI or Normalized Difference Vegetation Index NDVI, several new indices has been proposed during the past decade as potential physiological indicators. In this paper, the performance of several of them for determining the physiological status of the foliage is evaluated on an experimental Norway spruce needles (Picea abies (L.) Karst) plot. Four needle classess of 27 years old spruce have been sampled throughout cloudy and sunny day. Needle classes were represented by the needles of the branchlets of the 4th, 7th, 9th and 12th whorls. Study was conducted on one-year old needles and sampling ran over several times a day to separate influence of dynamic processess on parameters. Results show that the ratio of reflectance in the green and red region (presented as ratio of reflectance at 560 nm and 694 nm) outperforms the others examinated vegetation indices, and suggest that it would be best suited for the characterization of the leaf status. Being always the highest in the uppermost part of the crown and the lowest in shaded part of the crown, parameter is strictly stratificated throughout the crown. Furthermore, parameter values correspond with intensity of physiological processess ongoing in needles during midday. The values of the other indicators seem to be affected by leaf pigment content and morphology too much. Neither PRI nor NDVI were able to distinguish differences in needle properties sufficiently.