The 3D construction of leaves is coordinated with water use efficiency in conifers

Abstract

Conifers prevail in the canopies of many terrestrial biomes, holding a great ecological and economic importance globally. Current increases in temperature and aridity are resulting in conifer mortality and imposing high transpirational demands to global vegetation. Therefore, identifying leaf structural determinants of carbon acquisition and water use efficiency is essential in predicting physiological impacts due to environmental variation. Using synchrotron-generated microCT imaging, we extracted leaf volumetric anatomy and stomatal traits in 34 species across the conifers with a special focus on Pinus, the richest conifer genus. We show that intrinsic water use efficiency (WUEi) is driven by leaf vein volume, with both traits scaling positively. The ratios of stomatal pore number per unit mesophyll or intercellular airspace volume emerged as powerful explanatory variables, accurately predicting both stomatal conductance and WUEi. Our results clarify how the three-dimensional organization of tissues within the leaf has a direct impact on plant water use and carbon uptake

Structural and functional leaf diversity lead to variability in photosynthetic capacity across a range of Juglans regia genotypes

“…Leaf anatomy also plays an important role in biophysical coordination between CO 2 diffusion and leaf hydraulics (Boyce et al, 2009; Lehmeier et al, 2017; Fulton et al, 2017). Similar to findings from Trueba et al (2022), J. regia accessions with greater porosity had less V vein / V leaf and lower WUE i (Figure ) associated with higher g s . More extensive vasculature, including greater bundle sheath extensions, may improve WUE i by improving connections between the vascular tissue and epidermis for stomatal regulation and water supply to replace losses due to transpiration (Brodribb et al, 2007; Zwieniecki et al, 2007).…”

“…Vein volume relative to the leaf volume ratio ( V vein / V leaf , m 3 m −3 ) was calculated as a fraction of total leaf volume as described by Trueba et al (2022) from the same scans used for θ IAS , τ and λ leaf calculations.…”

Catastrophic hydraulic failure and tipping points in plants

“…Water must be transported apoplastically through the leaf venation system and may also be transported apoplastically along the cell walls of mesophyll tissue before evaporating into intercellular spaces. However, many leaves contain endodermis‐like bundle sheaths around the vascular tissue (Lersten, 1997; Liesche et al, 2021; Trueba et al, 2022) that may force water through the symplast of the bundle sheath. Further, the bundle sheath (suberized or not) exerts strong control over whole leaf hydraulic transport and aquaporins appear to be involved in water movement across the bundle sheath (Moshelion et al, 2015; Shatil‐Cohen et al, 2011).…”

“…Further, the bundle sheath (suberized or not) exerts strong control over whole leaf hydraulic transport and aquaporins appear to be involved in water movement across the bundle sheath (Moshelion et al, 2015; Shatil‐Cohen et al, 2011). The pathways of water through leaves are complex and less well‐understood than those through xylem but new modelling and imaging developments are expanding the understanding of leaf water transport (Albuquerque et al, 2020; Trueba et al, 2022). One of the largest unknowns in symplastic transport of leaves and roots is knowledge of individual cell water transport properties and how they vary through time but also with species and in different organs.…”

“…Water must be transported apoplastically through the leaf venation system and may also be transported apoplastically along the cell walls of mesophyll tissue before evaporating into intercellular spaces. However, many leaves contain endodermis-like bundle sheaths around the vascular tissue (Lersten, 1997;Liesche et al, 2021;Trueba et al, 2022) that may force water through the symplast of the bundle sheath.…”