| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
American Journal of Botany, Vol 84, 1223, Copyright © 1997 by Botanical Society of America, Inc.
PHYSIOLOGY AND DEVELOPMENT |
MJ Canny
A test was made of the previous unexpected observation that embolized vessels were refilled during active transpiration. The contents of individual vessels in petioles of sunflower plants were examined, after snap-freezing at 2-h intervals during a day's transpiration, in the cryo-scanning electron microscope, and assessed for the presence of liquid or gas (embolism) contents. Concurrent measurements were made of irradiance, leaf temperature, transpiration rate, and leaf water potential (by pressure chamber). Up to 40% of the vessels were already embolized by 0900 (transpiration rate ~5 _g_cm-2_s-1, water potential about -300 J/kg), and the proportion declined to a minimum (as low as 4%) at 1500. This was the time of highest transpiration rate (~25 _g_cm-2_s-1) and most negative water potential (-600 to -700 J/kg). Images of vessels with mixed gas and liquid contents showed water being extruded through pits in the walls of the vessels to refill them. The data indicate that: (1) the water columns are weak and break under quite small tensions; (2) embolisms are repaired by refilling the vessels with water on a short time scale (minutes) throughout the day; (3) the vigor of this refilling process is adjusted by the plant on a longer time scale (hours) to the intensity of the water stress; (4) the pressure chamber balance pressure (P) does not measure tension in the vessels; (5) P is also not a measure of water stress (as measured by vessel embolization); and (6) P is a measure of the plant's response to water stress, i.e., a measure of the vigor of the refilling process. The test confirms the previous observations and negates all the assumptions and evidences of the Cohesion Theory. The data are fully consistent with the Compensating Pressure Theory, which predicted the relations demonstrated in this experiment. Using the assumptions of that theory it is easy to outline a simple mechanism by which the refilling of vessels might be achieved by reverse osmosis, and the adjustment in (3) might be achieved by osmoregulation in the starch sheath.
This article has been cited by other articles:
|
|
 |
|
  A.-C. Tang and J. S. Boyer Xylem tension affects growth-induced water potential and daily elongation of maize leaves J. Exp. Bot., March 1, 2008; 59(4): 753 - 764. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 T.W.J. Scheenen, F.J. Vergeldt, A.M. Heemskerk, and H. Van As Intact Plant Magnetic Resonance Imaging to Study Dynamics in Long-Distance Sap Flow and Flow-Conducting Surface Area Plant Physiology, June 1, 2007; 144(2): 1157 - 1165. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
D. Hukin, H. Cochard, E. Dreyer, D. L. Thiec, and M. B. Bogeat-Triboulot Cavitation vulnerability in roots and shoots: does Populus euphratica Oliv., a poplar from arid areas of Central Asia, differ from other poplar species? J. Exp. Bot., August 1, 2005; 56(418): 2003 - 2010. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 H. Taneda and M. Tateno The criteria for biomass partitioning of the current shoot: water transport versus mechanical support Am. J. Botany, December 1, 2004; 91(12): 1949 - 1959. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
H. Cochard, F. Froux, S. Mayr, and C. Coutand Xylem Wall Collapse in Water-Stressed Pine Needles Plant Physiology, January 1, 2004; 134(1): 401 - 408. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J. S. Sperry, V. Stiller, and U. G. Hacke Xylem Hydraulics and the Soil-Plant-Atmosphere Continuum: Opportunities and Unresolved Issues Agron. J., November 1, 2003; 95(6): 1362 - 1370. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A.-C. Tang and J. S. Boyer Root pressurization affects growth-induced water potentials and growth in dehydrated maize leaves J. Exp. Bot., November 1, 2003; 54(392): 2479 - 2488. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
P. Trifilo, A. Gasco, F. Raimondo, A. Nardini, and S. Salleo Kinetics of recovery of leaf hydraulic conductance and vein functionality from cavitation-induced embolism in sunflower J. Exp. Bot., October 1, 2003; 54(391): 2323 - 2330. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. T. Tyree and H. Cochard Vessel contents of leaves after excision: a test of the Scholander assumption J. Exp. Bot., September 1, 2003; 54(390): 2133 - 2139. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
H. Cochard, S. Forestier, and T. Ameglio A new validation of the Scholander pressure chamber technique based on stem diameter variations J. Exp. Bot., June 1, 2001; 52(359): 1361 - 1365. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. A. Zwieniecki, P. J. Melcher, and N. M. Holbrook Hydraulic properties of individual xylem vessels of Fraxinus americana J. Exp. Bot., February 1, 2001; 52(355): 257 - 264. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. J. Canny Contributions to the debate on water transport Am. J. Botany, January 1, 2001; 88(1): 43 - 46. [Abstract] [Full Text]
|
|
|
|
|
|
M. J. Canny Embolisms and refilling in the maize leaf lamina, and the role of the protoxylem lacuna Am. J. Botany, January 1, 2001; 88(1): 47 - 51. [Abstract] [Full Text]
|
|
|
|
|
|
R. S. Pearce and M. P. Fuller Freezing of Barley Studied by Infrared Video Thermography Plant Physiology, January 1, 2001; 125(1): 227 - 240. [Abstract] [Full Text]
|
|
|
|
|
|
H. Cochard, C. Bodet, T. Améglio, and P. Cruiziat Cryo-Scanning Electron Microscopy Observations of Vessel Content during Transpiration in Walnut Petioles. Facts or Artifacts? Plant Physiology, November 1, 2000; 124(3): 1191 - 1202. [Abstract] [Full Text]
|
|
|
|
|
|
M. A. Zwieniecki and N. M. Holbrook Bordered Pit Structure and Vessel Wall Surface Properties. Implications for Embolism Repair Plant Physiology, July 1, 2000; 123(3): 1015 - 1020. [Abstract] [Full Text]
|
|
|
|
|
|
Y. Utsumi, Y. Sano, R. Funada, S. Fujikawa, and J. Ohtani The Progression of Cavitation in Earlywood Vessels of Fraxinus mandshurica var japonica during Freezing and Thawing Plant Physiology, November 1, 1999; 121(3): 897 - 904. [Abstract] [Full Text]
|
|
|
|
|
|
J. P Comstock Why Canny's theory doesn't hold water Am. J. Botany, August 1, 1999; 86(8): 1077 - 1081. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
V. Stiller and J. S Sperry Canny's compensating pressure theory fails a test Am. J. Botany, August 1, 1999; 86(8): 1082 - 1086. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
N. M. Holbrook and M. A. Zwieniecki Embolism Repair and Xylem Tension: Do We Need a Miracle? Plant Physiology, May 1, 1999; 120(1): 7 - 10. [Full Text]
|
|
|
|
|
|
M. T. Tyree, S. Salleo, A. Nardini, M. Assunta Lo Gullo, and R. Mosca Refilling of Embolized Vessels in Young Stems of Laurel. Do We Need a New Paradigm? Plant Physiology, May 1, 1999; 120(1): 11 - 22. [Abstract] [Full Text]
|
|
|
|
|
|
M. E. McCully Root Xylem Embolisms and Refilling. Relation to Water Potentials of Soil, Roots, and Leaves, and Osmotic Potentials of Root Xylem Sap Plant Physiology, March 1, 1999; 119(3): 1001 - 1008. [Abstract] [Full Text]
|
|
|
|
 |
|
 A. Ennos The aerodynamics and hydrodynamics of plants J. Exp. Biol., January 12, 1999; 202(23): 3281 - 3284. [Abstract] [PDF]
|
|
|
|
|
|
F. Barrieu, F. Chaumont, and M. J. Chrispeels High Expression of the Tonoplast Aquaporin ZmTIP1 in Epidermal and Conducting Tissues of Maize Plant Physiology, August 1, 1998; 117(4): 1153 - 1163. [Abstract] [Full Text]
|
|
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
