Fig. 1. (a) Thermal image of side view of grapevine row from c. 1.5 m; (b) correction image obtained of a constant temperature object (lens cap) taken after running the camera for 30 min; (c) corrected version of original image obtained after subtraction of (b) from (a) and adding back the mean temperature of (b)
Use of infrared thermography for monitoring stomatal closure in the field: application to grapevine
Jones H. G., Stoll M., Santos T., de Sousa C., Chaves M. M., Grant O. M. (2002)
Hamlyn G. Jones, 1,4, Manfred Stoll, 1, Tiago Santos, 2, Claudia de Sousa, 3, M. Manuela Chaves, 2,3 and Olga M. Grant, 1
1 Division of Environmental and Applied Biology, School of Life Sciences, University of Dundee, SCRI, Invergowrie, Dundee DD2 5DN, UK
2 Instituto Superior de Agronomia, Tapada da Ajuda, 1349-017 Lisboa, Portugal
3 Instituto de Tecnologia QuõÂmica e BioloÂgica, Av. Republica, EAN. 2784-505 Oeiras, Portugal
in Journal of Experimental Botany 53: 2249–2260 – PMID: 12379792 –
This paper reviews and discusses strategies for the use of thermal imaging for studies of stomatal conductance in the field and compares techniques for image collection and analysis.
Measurements were taken under a range of environmental conditions and on sunlit and shaded canopies to illustrate the variability of temperatures and derived stress indices. A simple procedure is presented for correcting for calibration drift within the images from the low-cost thermal imager used (SnapShot 225, Infrared Solutions, Inc.).
The use of wet and dry reference surfaces as thresholds to eliminate the inclusion of non-leaf material in the analysis of canopy temperature is discussed. An index that is proportional to stomatal conductance was compared with stomatal measurements with a porometer.
The advantages and disadvantages of a possible new approach to the use of thermal imagery for the detection of stomatal closure in grapevine canopies, based on an analysis of the temperature of shaded leaves, rather than sunlit leaves, are discussed.
Evidence is presented that the temperature of reference surfaces exposed within the canopy can be affected by the canopy water status.