Abstract
In spite of the significant progress made in recent years, the use of thermography to derive biologically relevant traits remains a challenge under fluctuating conditions. The aim of this study was to rethink the current method to process thermograms and derive temporal responses of stomatal conductance (gsw) using dynamic energy balance equations. Time-series thermograms provided the basis for a spatial and temporal characterization of gsw responses in wheat (Triticum aestivum). A leaf replica with a known conductance was used to validate the approach and to test the ability of our model to be used with any material and under any environmental conditions. The results highlighted the importance of the co-ordinated stomatal responses that run parallel to the leaf blade despite their patchy distribution. The diversity and asymmetry of the temporal response of gsw observed after a step increase and step decrease in light intensity can be interpreted as a strategy to maximize photosynthesis per unit of water loss and avoid heat stress in response to light flecks in a natural environment. This study removes a major bottleneck for plant phenotyping platforms and will pave the way to further developments in our understanding of stomatal behaviour.
Highlights
After a period of increased crop production over the past 50 years (Wik et al, 2008; Pingali, 2012; Tillman et al, 2015), increases in yield have fallen to ~1% per annum (Fischer and Edmeades, 2010; Ramankutty et al, 2018)
Despite the success of thermometry in selecting plants with improved yield or altered response to drought (Raskin and Ladyman, 1988; Reynolds et al, 1999; Merlot et al, 2002), a major limitation of this technique is the need for stable environmental conditions to interpret the temperature differences (Reynolds et al, 1999; Jones et al, 2009; Rischbeck et al, 2017; Prado et al, 2018).The results presented here provide strong evidence that thermography can be used to derive gsw under a dynamic environment, opening up a new avenue for plant phenotyping and selection
Our approach to describe the combination of leaf energy balance and mass transfer does not depend on any specific reference material or environmental conditions, making this method a versatile tool for thermography
Summary
After a period of increased crop production over the past 50 years (Wik et al, 2008; Pingali, 2012; Tillman et al, 2015), increases in yield have fallen to ~1% per annum (Fischer and Edmeades, 2010; Ramankutty et al, 2018). To meet the increasing food demand, crop yield needs to increase at a rate of 2.4% per annum over the few decades (Tilman et al, 2011; Ray et al, 2012, 2013; Long et al, 2015). Many of the current commercial wheat cultivars have been bred with yield as the main target trait, an approach that is reaching its limit in term of potential improvement (Fischer and Rebetzke, 2018). The natural genetic diversity between cultivars or landraces provides the opportunity to discover desirable traits (e.g. resistance to pest or stress; high water use efficiency) that, when crossed with high-yielding varieties, could produce progenies with improved performance
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