Journal Article

Contrasting hydraulic architecture and function in deep and shallow roots of tree species from a semi-arid habitat

Johnson, Daniel M, Brodersen, Craig R, Domec, Jean-Christophe, Duke University [Durham], Reed, Mary, University of Florida [Gainesville] (UF), Transfert Sol-Plante et Cycle des Eléments Minéraux dans les Ecosystèmes Cultivés (TCEM) ; Institut National de la Recherche Agronomique (INRA)-École Nationale d'Ingénieurs des Travaux Agricoles - Bordeaux (ENITAB), Jackson, Robert B

2014

Overview

Background and AimsDespite the importance of vessels in angiosperm roots for plant water transport, there is little research on the microanatomy of woody plant roots. Vessels in roots can be interconnected networks or nearly solitary, with few vessel–vessel connections. Species with few connections are common in arid habitats, presumably to isolate embolisms. In this study, measurements were made of root vessel pit sizes, vessel air-seeding pressures, pit membrane thicknesses and the degree of vessel interconnectedness in deep (approx. 20 m) and shallow (<10 cm) roots of two co-occurring species, Sideroxylon lanuginosum and Quercus fusiformis.MethodsScanning electron microscopy was used to image pit dimensions and to measure the distance between connected vessels. The number of connected vessels in larger samples was determined by using high-resolution computed tomography and three-dimensional (3-D) image analysis. Individual vessel air-seeding pressures were measured using a microcapillary method. The thickness of pit membranes was measured using transmission electron microscopy.Key ResultsVessel pit size varied across both species and rooting depths. Deep Q. fusiformis roots had the largest pits overall (>500 µm) and more large pits than either shallow Q. fusiformis roots or S. lanuginosum roots. Vessel air-seeding pressures were approximately four times greater in Q. fusiformis than in S. lanuginosum and 1·3–1·9 times greater in shallow roots than in deep roots. Sideroxylon lanuginosum had 34–44 % of its vessels interconnected, whereas Q. fusiformis only had 1–6 % of its vessels connected. Vessel air-seeding pressures were unrelated to pit membrane thickness but showed a positive relationship with vessel interconnectedness.ConclusionsThese data support the hypothesis that species with more vessel–vessel integration are often less resistant to embolism than species with isolated vessels. This study also highlights the usefulness of tomography for vessel network analysis and the important role of 3-D xylem organization in plant hydraulic function.

• Publisher: Oxford University Press (OUP),HAL CCSD,Oxford University Press
• Subject: anatomy & histology / Biodiversity and Ecology / Biological Transport / Caves / Cavitation flow / computed tomography / Ecosystem / embolism / Embolisms / Environmental Sciences / habitats / Hydraulics / image analysis / metabolism / Microscopy, Electron, Scanning / Original / physiology / Plant cells / Plant Roots / Plant Roots - anatomy & histology / Plant Roots - physiology / Plant Roots - ultrastructure / Plant Transpiration / Plant Transpiration - physiology / Quercus / Quercus - anatomy & histology / Quercus - physiology / Quercus - ultrastructure / rooting / Rooting depth / roots / Sapotaceae / Sapotaceae - anatomy & histology / Sapotaceae - physiology / Sapotaceae - ultrastructure / scanning electron microscopy / Seeding / Sideroxylon / Tomography, X-Ray Computed / Trees / ultrastructure / Vascular plants / Water / Water - metabolism / Wood / Wood - anatomy & histology / Wood - physiology / Wood - ultrastructure / woody plants / Xylem / Xylem - anatomy & histology / Xylem - physiology / Xylem - ultrastructure
• ISBN: 0003322517000