The hydraulic architecture of the leaf lamina fits an area preserving design
The leaf is the terminal part of the water transport system in plants. It represents the organ where the largest amount of the hydraulic resistance is located, greatly affecting the water economy. Different theoretical models and empirical data on the network structure have been reported, questioning the existence of a possible universal structure. Details on conduit size, degree of widening, number of conduits and area supplied are relatively lacking. Our aim was to provide new anatomical information useful for defining the architectural design in angiosperm leaves. We examined the xylem of leaf midribs and petioles of young Acer pseudoplatanus saplings and measured the hydraulic diameter (Dh) and the number of conduits within the veins. We also measured the number of conduits and their total conductive area supplying the downstream leaf area. We tested the existence of widened structure along the network and how the total conductive area and conduit number scale with the leaf area. Our results suggested that the degree of widening along the midrib (L) in the leaf was higher (Dh~L0.45) than in the stem (~0.2). The number of conduits per leaf area suggested a certain degree of furcation of conduits towards the petiole base. The furcation in the midrib seemed to be prominent in the first cm of the leaf tip, decreasing along the midrib. In the petiole a constant number of conduits was observed. The total conductive area scaled isometrically with the downstream lamina area suggesting that the vein network within the lamina fits the area-preserving design. This design was achieved by arranging the degree of widening and the furcation rate. In contrast, along the petiole and in the stem the constant number of conduits and the cell widening indicates an area decreasing design.
Lechthaler, S., Gazzabin, M. and Anfodillo, T. (2018). The hydraulic architecture of the leaf lamina fits an area preserving design. Acta Hortic. 1222, 43-48
conduits widening, leaf, hydraulic architecture, hydraulic diameter, veins anatomy