Time-Lapse Study: Heterogeneous Response to Light Changes in Wheat Leaf Stomata

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Although thermography allows rapid, non-invasive measurements of large numbers of plants, it has not been used extensively due to the difficulty in deriving biologically relevant information such as leaf transpiration (E) and stomatal conductance (gsw) from thermograms. Methods normalizing leaf temperature using temperatures from reference materials (e.g. with and without evaporative flux) to generate stress indices are generally preferred due to their ease of use to assess plant water status. Here, a simplified method to solve dynamic energy balance equations is presented, which enables the calculation of ‘wet’ and ‘dry’ leaf temperatures in order to derive stress indices, whilst providing accurate estimates of E and gsw. Comparing stress indices and gas exchange parameters highlights the limitation of stress indices in a dynamic environment and how this problem can be overcome using artificial leaf references with known conductance. Additionally, applying the equations for each pixel of a thermogram to derive the rapidity of stomatal response over the leaf lamina in wheat revealed the spatial heterogeneity of stomatal behaviour. Rapidity of stomatal movements is an important determinant of water use efficiency, and our results showed ‘patchy’ responses that were linked to both the spatial and temporal response of gsw.

This video visualizes the dynamic and spatially varying response of stomatal conductance over the leaf lamina of spring wheat ‘Paragon’ (Triticum aestivum L.) when light intensity changes. We examine five wheat plants subjected to both step increases and decreases in light. Observe the temporal and spatial heterogeneity of stomatal conductance across the leaf surface as light levels fluctuate. See how different regions of the leaf lamina respond differently and at different rates to changes in light intensity. This video provides a visual representation of the complex stomatal behavior in wheat leaves under dynamic light conditions, highlighting the importance of considering leaf-level heterogeneity in plant physiology studies.

Keywords: Wheat, Patchy response, Stomatal conductance, Stress indices, Thermal imaging, Transpiration

Citation:
Silvere Vialet-Chabrand, Tracy Lawson, Thermography methods to assess stomatal behaviour in a dynamic environment, Journal of Experimental Botany, Volume 71, Issue 7, 6 April 2020, Pages 2329–2338, https://doi.org/10.1093/jxb/erz573

Published on: 08 January 2020

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