How are leaf mechanical properties and water‐use traits coordinated by vein traits? A case study in Fagaceae

Abstract

1. Leaf venation is a key trait determining leaf water relations, phloem transport and mechanical stability. However, since the contribution of leaf veins to mechanical properties has not been properly understood, our understanding of how leaf vein architecture adjusts these functions within leaves and across species as well as its mechanistic basis is also limited. Here, we tested the hypotheses that leaf water-use and mechanical properties would be more correlated with lower-and higher-order vein density (VLA), respectively. 2. We studied eight Fagaceae species growing in temperate forests in Japan and differing in secondary vein patterns, leaf habits, size and natural habitat. We quantified two leaf water-use traits [lamina hydraulic conductance (K lamina ) and carbon stable isotope ratio (d 13 C)], two mechanical properties [lamina tensile strength and tensile modulus of elasticity (E)] and nine traits relating to both vein architecture and leaf structure. 3. Across species, primary and secondary vein density (VLA 1Á2 ) correlated positively to lamina strength and leaf structural traits (leaf area and leaf mass per area) but not to water use. In contrast, minor vein density (VLA min ) correlated to K lamina positively but not to mechanical properties and leaf structural traits. Water-use traits and mechanical properties were independent on both area and mass basis. 4. Our results indicate that there is labour sharing in leaf functions among higher-and lowerorder veins, that VLA 1Á2 influences leaf structural and mechanical properties and that VLA min affects leaf water use and, thus, potentially the gas exchange capacity. These findings suggest that vein hierarchy is associated with functional differentiation among vein orders to support leaf functions. This system possesses different vein orders that are quantitatively and qualitatively different within leaves to carry out multiple functions. Therefore, the evolutionary or accumulative shift in vein hierarchy might explain the variation in leaf structure and functions.

Coordination and Determinants of Leaf Community Economics Spectrum for Canopy Trees and Shrubs in a Temperate Forest in Northeastern China

“…Soil water may be tightly correlated to plant hydraulic architecture [40]. For leaves, however, the LES traits were found to be commonly uncorrelated with hydraulic traits [28,41]. That might explain why we were unable to find the expected relationship between leaf community economics spectrum and soil water content.…”

Competition for epidermal space in the evolution of leaves with high physiological rates

“…For example, leaf strength is correlated to major vein density but not minor veins (e.g. Kawai & Okada, ). Also, a transition occurs from vessel‐based xylem in major veins (transporting water mostly along the vein path) to tracheid‐based minor veins (promoting radial distribution of water; Esau, ; Zwieniecki et al ., ).…”

Leaf water relations and structural traits of four temperate woody species occurring in serpentine and non‐serpentine soil

“…As an index for leaf hydraulic conductance (e.g., Kawai & Okada, ; Scoffoni et al, ), we measured the density of minor vein (VLA min ). One piece ( c .…”

“…As an index for leaf hydraulic conductance (e.g., Kawai & Okada, 2016;Scoffoni et al, 2016), we measured the density of minor vein (VLA min ). One piece (c. 1.5 × 1.5 cm 2 ), obtained from the middle of the leaf lamina of each individual, was chemically-cleared by 5% NaOHaq for 1-3 days and stained with 1% safranin.…”