Book contents
- Frontmatter
- Contents
- List of contributors
- Preface
- 1 Global change and plant water relations
- 2 Cavitation. A review: past, present and future
- 3 Effect of cavitation on the status of water in plants
- 4 Stomatal control of xylem cavitation
- 5 Refilling of embolized xylem
- 6 Interpretation of the dynamics of plant water potential
- 7 A proposed mechanism of freezing and thawing in conifer xylem
- 8 Winter xylem embolism and spring recovery in Betula cordifolia, Fagus grandifolia, Abies balsamea and Picea rubens
- 9 Drought resistance strategies and vulnerability to cavitation of some Mediterranean sclerophyllous trees
- 10 Relations between sap velocity and cavitation in broad-leaved trees
- 11 NMR and water transport in plants
- 12 The symplast radial-axial water transport in plants: a NMR approach
- 13 Reproductive adaptation by polyembryony of coniferous forest trees under climatic stress as revealed by the metabolism of tritiated water
- 14 A heat balance method for measuring sap flow in small trees
- 15 Heat pulse measurements on beech (Fagus sylvatica L.) in relation to weather conditions
- 16 Extremely fast changes of xylem water flow rate in tall trees caused by atmospheric, soil and mechanic factors
- 17 Water relations and water transport in coppice vs. single stem Quercus cerris L. trees
- 18 Environmental control of water flux through Maritime pine (Pinus pinaster Ait).
- 19 Evaluation of transpiration of apple trees and measurement of daily course of water flow within the main branches of walnut trees
- 20 Estimating citrus orchard canopy resistance from measurements of actual and potential transpiration
- 21 Stomatal conductance in tomato responds to air humidity
- 22 Water relations of Canarian laurel forest trees
- 23 Watering regime and photosynthetic performance of Gunnera tinctoria (Molina) Mirbel.
- 24 Water relations and ultrasound emissions in Douglas-fir seedlings infected with xylem pathogens
- 25 Diurnal fruit shrinkage: a model
- 26 Analysis of pressure-volume curves by non-linear regression
- 27 Determination of the amount of apoplastic water and other water relations parameters in conifer needles
- 28 The assessment of water status in chilled plants
- 29 An artificial osmotic cell: a model system for studying phenomena of negative pressure and for determining concentrations of solutes
- 30 Measurement of water and solute uptake into excised roots at positive and negative root pressures
- Index
7 - A proposed mechanism of freezing and thawing in conifer xylem
Published online by Cambridge University Press: 04 August 2010
- Frontmatter
- Contents
- List of contributors
- Preface
- 1 Global change and plant water relations
- 2 Cavitation. A review: past, present and future
- 3 Effect of cavitation on the status of water in plants
- 4 Stomatal control of xylem cavitation
- 5 Refilling of embolized xylem
- 6 Interpretation of the dynamics of plant water potential
- 7 A proposed mechanism of freezing and thawing in conifer xylem
- 8 Winter xylem embolism and spring recovery in Betula cordifolia, Fagus grandifolia, Abies balsamea and Picea rubens
- 9 Drought resistance strategies and vulnerability to cavitation of some Mediterranean sclerophyllous trees
- 10 Relations between sap velocity and cavitation in broad-leaved trees
- 11 NMR and water transport in plants
- 12 The symplast radial-axial water transport in plants: a NMR approach
- 13 Reproductive adaptation by polyembryony of coniferous forest trees under climatic stress as revealed by the metabolism of tritiated water
- 14 A heat balance method for measuring sap flow in small trees
- 15 Heat pulse measurements on beech (Fagus sylvatica L.) in relation to weather conditions
- 16 Extremely fast changes of xylem water flow rate in tall trees caused by atmospheric, soil and mechanic factors
- 17 Water relations and water transport in coppice vs. single stem Quercus cerris L. trees
- 18 Environmental control of water flux through Maritime pine (Pinus pinaster Ait).
- 19 Evaluation of transpiration of apple trees and measurement of daily course of water flow within the main branches of walnut trees
- 20 Estimating citrus orchard canopy resistance from measurements of actual and potential transpiration
- 21 Stomatal conductance in tomato responds to air humidity
- 22 Water relations of Canarian laurel forest trees
- 23 Watering regime and photosynthetic performance of Gunnera tinctoria (Molina) Mirbel.
- 24 Water relations and ultrasound emissions in Douglas-fir seedlings infected with xylem pathogens
- 25 Diurnal fruit shrinkage: a model
- 26 Analysis of pressure-volume curves by non-linear regression
- 27 Determination of the amount of apoplastic water and other water relations parameters in conifer needles
- 28 The assessment of water status in chilled plants
- 29 An artificial osmotic cell: a model system for studying phenomena of negative pressure and for determining concentrations of solutes
- 30 Measurement of water and solute uptake into excised roots at positive and negative root pressures
- Index
Summary
ABSTRACT
From the evidence of recent work on freezing in the conifer xylem, previous theories of how cavitation is avoided during freezing and thawing must be rejected. What may happen during freezing is that two pressure rises occur in the tracheid lumen. The first pressure rise occurs as the water expands on crystallising. The second pressure rise is caused by water being drawn out of freezing and unfrozen tracheid lumens, through cell wall capillaries and into the already frozen lumens.
Despite migration of water out of the lumen during freezing, enough water may subsequently be drawn back into the frozen lumen to provide positive pressures during thawing. If positive pressures occur, any bubbles nucleated during freezing quickly redissolve. If negative pressures occur in the xylem before the ice has fully thawed then transitory pit aspiration may occur. Pits may deaspirate when pressures in the thawed and thawing tracheids equalise.
INTRODUCTION
The cohesion-tension theory (Dixon & Joly, 1894) is widely accepted as the mechanism of the ascent of sap in tall trees. However, some aspects of this mechanism remain incompletely explained. One of these aspects is the effect of freezing and thawing on the conductivity of conifer xylem.
During freezing gases dissolved in water come out of solution and, at ice/water interface velocities above 2.5 mm s−1, gas bubbles nucleate (Bari & Hallet, 1974). Lybeck (1959), Sucoff (1969) and Robson, McHardy and Petty (1988) observed gas bubbles in frozen xylem tracheids. If bubbles are present in the tracheid lumen when the xylem sap is in tension (Le. at pressures below absolute vacuum) they may expand and cavitate individual tracheids.
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- Water Transport in Plants under Climatic Stress , pp. 75 - 85Publisher: Cambridge University PressPrint publication year: 1993
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