Abstract Detail

Development and Structure

Carvalho, Monica [1], Niklas, Karl [2].

Geometric Scaling and Hydraulic Architecture of Xylem and Phloem in Poplar and Ginkgo Leaves.

Leaf vasculature mediates the effective export of photosynthate and constitutes a major portion of the water transpiration pathway in leaves. Fluid flow properties affecting the transport of water and sugars are determined by the spatial arrangement and geometry of conducing conduits. Even though topological properties that are inherent to hierarchical and reticulated leaf vascular patterns typical of angiosperms have been described, the geometric relations in these branching systems that determine flow dynamics remain poorly known. A direct analysis on conducing tissue cross-sectional areas in leaf veins is needed to better test for mass-conserving or energy-conserving branching systems on leaves, and to address the implications of vein branching geometry on transport within leaves.
Phloem conduit dimensions across vein orders in leaves of poplar are not consistent with energy minimization models (e.g. Murray’s Law) that have been observed for xylem in open systems such as branches and compound leaf petiolules. At a leaf-scale, the total conductive area of phloem in this reticulate vascular system increases disproportionately with vein order, suggestive of a system that maximizes the conductive area or ‘catchment’ area of collecting veins. Whether this observation is an inherent property of reticulate leaf vascular systems, or a property specifically related to phloem tissues remains to be tested. Here, we evaluate and compare geometric scaling properties on xylem and phloem conduit dimensions in leaves of two model tree species with contrasting open dichotomous and reticulate leaf vascular topologies, Populus tremuloides x alba and Ginkgo biloba. Geometric relations between xylem and phloem conduits in each of these model species are used to estimate water transfer from xylem to phloem and consider the implications on phloem flow dynamics at the leaf level.

1 - Cornell University, School of Integrative Plant Sciences, Department of Plant Biology, 412 Mann Library Building, Ithaca, NY, 14853, United States
2 - Cornell University, Plant Biology, 412 Mann Library, ITHACA, NY, 14853-5908, USA

Keywords:
Leaf Architecture
leaf anatomy
morphology
Water transport.

Presentation Type: Oral Paper
Session: 29, Development and Structure I
Location: 202/Savannah International Trade and Convention Center
Date: Tuesday, August 2nd, 2016
Time: 2:30 PM
Number: 29005
Abstract ID:883
Candidate for Awards:Katherine Esau Award,Maynard F. Moseley Award