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Mar. 3rd, 2011 B4730/5730 Plant Physiological Ecology

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Presentation on theme: "Mar. 3rd, 2011 B4730/5730 Plant Physiological Ecology"— Presentation transcript:

1 Mar. 3rd, 2011 B4730/5730 Plant Physiological Ecology
Water Transport I

2 Root Anatomy and Water Relations
Tradeoffs between safety and efficiency Exodermis Roots hairs, mycorrhizae Casparian strip Apoplast and symplast Transcellular Endodermis Root branching Stele Secondary growth, cambium Xylem and phloem Root cap

3 Agave deserti; North et al. 2004 PCE

4 Root Water and Aquaporins Transport
Agave deserti; North et al PCE

5 Pressure Volume Curves
Relationship between tissue pressure and volume describe effect of dehydration Uses Boyle-Mariotte Law that PV=constant Ψ is substitute for pressure Extrapolation to Ψπ Relative Water Content substitute for volume Graphs drawn with 1/RWC ε derived from nonlinearity between full turgor and turgor loss point Osmotic adjustment shifts turgor loss point to lower RWC

6 Niinemets Ecology 2001

7 Glyricidia sepium Brodribb & Holbrook Plant Phys. 2003

8 Brodribb & Holbrook Plant Phys. 2003;
dotted lines 80% and 20% maximum gs

9 Salt Effects Phillyrea latifolia; Tattini et al. 2002

10 Cohesion-Tension Theory
Dixon in late 19th century proposed water transport to top of tall plants by cohesion/tension Driven by soil to air water potential gradient Hydrogen-bonding creates tension Challenged throughout 1990s Alternatives included metabolic pumping Centrifuge and killed wood provided very strong support of cohesion-tension

11 Soil Water Movement Soil Texture Changes Soil Water Characteristic curves Coarse textured soils hold less water less tightly than fine texture soils Soil hydraulic conductance changes Calculating available water requires knowledge of soil water content dynamics and rooting depth H2O = Θ·depth Benefit of fine textured soils for plant water drops with decreasing precipitation Transition at 400mm (Noy-Meir 1973)

12 Water Transport in Xylem
Overproduction of vascular tissue is wasteful and underproduction restricts growth Plant transport system is efficient yet a large proportion of the decrease in leaf water potential is from hydraulic conductance (20-60%) Hydraulic conductance dynamics depends on length Area of Xylem Number, type and size distribution of xylem conduits Cavitation

13 Pinus taeda, PCE Ewers et al. 2000

14 Mencuccini et al PCE

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