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Climate change-driven drought events are becoming unescapable in an increasing number of areas worldwide. Understanding how plants are able to adapt to these changing environmental conditions is a non-trivial challenge. Physiologically, improving a plant’s intrinsic water use efficiency (WUEi) will be essential for plant survival in dry conditions. Physically, plant adaptation and acclimatisation are constrained by a plant’s anatomy. In other words, there is a strong link between anatomical structure and physiological function. Former research predominantly focussed on using 2D anatomical measurements to approximate 3D structures based on the assumption of ideal shapes, such as spherical spongy mesophyll cells. As a result of increasing progress in 3D imaging technology, the validity of these assumptions is being assessed, and recent research has indicated that these approximations can contain significant errors. We suggest to invert the workflow and use the less common 3D assessments to provide corrections and functions for the more widely available 2D assessments. By combining these 3D and corrected 2D anatomical assessments with physiological measurements of WUEi, our understanding of how a plant’s physical adaptation affects its function will increase and greatly improve our ability to assess plant survival. 

As the site of almost all terrestrial carbon fixation, the mesophyll tissue is critical to leaf function. However, mesophyll tissue is not restricted only to leaves but also occurs in the laminar, heterotrophic organs of the floral perianth, providing a powerful test of how metabolic differences are linked to differences in tissue structure. Here, we compared mesophyll tissues of leaves and flower perianths of six species using high-resolution X-ray computed microtomography (microCT) imaging. Consistent with previous studies, stomata were nearly absent from flowers, and flowers had a significantly lower vein density compared to leaves. However, mesophyll porosity was significantly higher in flowers than in leaves, and higher mesophyll porosity was associated with more aspherical mesophyll cells. Despite these differences in cell and tissue structure between leaf and flower mesophyll, modeled intercellular airspace conductance did not differ significantly between organs, regardless of differences in stomatal density between organs. These results suggest that in addition to differences between leaves and flowers in vein and stomatal densities, the mesophyll cells and tissues inside these organs also exhibit marked differences that may allow for flowers to be relatively cheaper in terms of biomass investment per unit of flower surface area. 

Traits in wild relatives of crop species can help breed sustainable crop varieties that produce more food with fewer resources. To make use of this variation, we need to find the genetic regions that allow wild species to use water and nutrients more efficiently. Leaf anatomy has a major effect on photosynthesis by determining rates of carbon gain and water loss. However, finding the genetic regions underlying leaf anatomical evolution has been limited by low-throughput and low-resolution trait measurements. 3D imaging using X-ray microcomputed tomography (μCT) may overcome these obstacles by providing high-throughput, high-resolution data on leaf anatomy. Compared to traditional 2D methods for leaf anatomy, 3D imaging captures physiologically important volumetric traits, is less biased, and encompasses a larger leaf area. We used synchrotron μCT to measure leaf anatomy on two tomato species Solanum lycopersicum (cultivated tomato) and S. pennellii (wild, drought-tolerant species), and four introgression lines containing loci that alter leaf anatomy. We measured stomatal density, size, and 3D arrangement, as well as leaf thickness and mesophyll porosity. Preliminary analyses show that synchrotron μCT can identify previously described quantitative trait loci for stomatal traits and leaf thickness and show how those traits are related to 3D leaf anatomy. We will use finite element models to show how these anatomical differences may contribute to genetic variation leaf CO2 and water vapour exchange.