Abstract Detail

Developmental and Structural Section

Schulte, Paul J [1], Hacke, Uwe [2], Schoonmaker, Amanda [3].

Computational fluid dynamics models of water flow through bordered pits in Picea glauca and Picea mariana roots and stems.

Water flow along the xylem for tracheid-bearing plants depends on flow through bordered pits, which for many conifers include a torus and a pit membrane comprised of large numbers of pores. Recently, an approach based on the engineering-derived field of computational fluid dynamics has enabled the detailed study of these pits, particularly with regard to flow through the pit membrane. The present study of bordered pits in two conifer species (Picea glauca and Picea mariana) considered tracheids from roots and stems. Scanning electron micrographs of pit structures were used to build 3D models of the pits, forming the geometry for which solutions of the Navier-Stokes equation were obtained. Flow rates and pressures were used to calculate hydraulic resistance for the entire pit as well as the portion of resistance attributable to each component of the pit (pit borders, torus, and margo pores).The total resistance to flow through the bordered pit was significantly greater for P. mariana compared to P. glauca. These species differences were primarily associated with the pit membrane (margo) component of pit resistance, which was greater in P. mariana because the margo pores were narrower. Although the pores in P. mariana pit membranes were more numerous, their narrower width resulted in a 2.7-fold greater membrane resistivity (resistance per unit area) as compared to P. glauca.The total resistance to flow through the bordered pit was significantly greater for stems as compared to roots and these differences were primarily due to the presence of more numerous margo pores occupying a greater total pore area in the pits of roots. Pits were also significantly wider in roots than in stems, contributing to the greater margo area but also to wider pit canals, leading to a significantly lower resistance of the pit canals. Flow on the basis of individual pit membrane pores was heavily dominated by the widest pores – although pit membranes had as many as 2500 pores, the largest 20 pores typically accounted for nearly half of the total flow through the pit. This study highlights the important role that computional models can play in helping to understand the interplay of xylem structure with the transport process.

Broader Impacts:

1 - Uinversity of Nevada, Las Vegas, Life Sciences, Las Vegas, NV, 89154-4004, USA
2 - University of Alberta, Renewable Resources, 442 Earth Sciences Building, Edmonton, AB, T6G 2E3, Canada
3 - University of Alberta, Renewable Resources, Edmonton, AB, T6G 2E3, Canada

Keywords:
xylem
bordered pits
hydraulic conductivity.

Presentation Type: Poster:Posters for Sections
Session: P
Location: Grand Salon A - D/Riverside Hilton
Date: Monday, July 29th, 2013
Time: 5:30 PM
Number: PDS019
Abstract ID:933
Candidate for Awards:None