scholarly journals Pit membrane chemistry influences the magnitude of ion-mediated enhancement of xylem hydraulic conductance in four Lauraceae species

2011 ◽  
Vol 31 (1) ◽  
pp. 48-58 ◽  
Author(s):  
E. Gortan ◽  
A. Nardini ◽  
S. Salleo ◽  
S. Jansen
Keyword(s):  
Hydraulic Conductance ◽  
Pit Membrane

scholarly journals Testing for ion-mediated enhancement of the hydraulic conductance of the leaf xylem in diverse angiosperms

2017 ◽  
Vol 4 ◽  
pp. e004 ◽  
Author(s):  
Christine Scoffoni ◽  
Grace John ◽  
Herve Cochard ◽  
Lawren Sack
Keyword(s):  
Water Solution ◽  
Pure Water ◽  
Xylem Sap ◽  
Hydraulic Conductance ◽  
Membrane Pores ◽  
Whole Plant ◽  
Pit Membrane ◽  
Major Bottleneck ◽  
The Difference ◽  
Xylem Conduits

Replacing ultra-pure water solution with ion solution closer to the composition of natural xylem sap increases stem hydraulic conductance by up to 58%, likely due to changes in electroviscosity in the pit membrane pores. This effect has been proposed to contribute to the control of plant hydraulic and stomatal conductance and potentially to influence on carbon balance during dehydration. However, this effect has never been directly tested for leaf xylem, which constitutes a major bottleneck in the whole plant. We tested for an ion-mediated increase in the hydraulic conductance of the leaf xylem (Kx) for seven species diverse in phylogeny and drought tolerance. Across species, no significant changes in Kx were observed between 0 and 15 mM KCl. We further tested for an effect of ion solution during measurements of Kx vulnerability to dehydration in Quercus agrifolia and found no significant impact. These results for leaf xylem contrast with the often strong ion effect reported for stems, and we suggest several hypotheses to account for the difference, relating to the structure of xylem conduits across vein orders, and the ultrastructure of leaf xylem pores. A negligible ion response in leaves would weaken xylem sap ion-mediated control of plant hydraulic conductance, facilitating modeling of whole plant hydraulic behavior and its influence on productivity.

Hydraulic conductance and tracheid anatomy in six species of extant seed plants

1988 ◽  
Vol 66 (6) ◽  
pp. 1073-1079 ◽  
Author(s):  
Paul J. Schulte ◽  
Arthur C. Gibson
Keyword(s):  
Capillary Flow ◽  
Large Diameter ◽  
Membrane Resistance ◽  
Hydraulic Conductance ◽  
Linear Increase ◽  
Biophysical Model ◽  
Lumen Diameter ◽  
Seed Plants ◽  
Pit Membrane ◽  
Conductance Increase

Hydraulic conductance of tracheids was studied in either petioles or young stems of six species of seed plants having various types of intertracheid pitting. Measured conductances were compared with estimates based on Hagen–Poiseuille flow through ideal capillaries and with predictions from a biophysical model incorporating observed anatomical characteristics of tracheids and intertracheid pits. Conductance of the xylem, expressed as a percentage of the ideal capillary flow prediction, varied from an average of 88% for a species containing only very narrow tracheids to less than 35% for species with large-diameter tracheids. The biophysical model allowed fairly close predictions of conductance for all species except one, where an estimate of the pit membrane resistance could not be experimentally obtained. For individual tracheids, conductance was largely a function of lumen diameter, pit membrane resistivity, and the exposed area of the pit membranes, as determined by pit shape, size, and frequency. For wide tracheids, scalariform-pitted elements showed a linear increase in conductance with an increase in lumen diameter; however, for tracheids with large circular pits, the conductance increase afforded by a wider lumen declines as lumen diameter increases. These model simulations demonstrate the increasing significance of intertracheid pitting in obstructing flow as lumen diameter increases.

Hydraulic Conductance and Xylem Structure in Tracheid-Bearing Plants

IAWA Journal ◽  
1985 ◽  
Vol 6 (4) ◽  
pp. 293-302 ◽  
Author(s):  
Arthur C. Gibson ◽  
Howard W. Calkin ◽  
Park S. Nobel
Keyword(s):  
Water Flow ◽  
Unit Length ◽  
Hydraulic Conductance ◽  
Distal Portion ◽  
Pteris Vittata ◽  
Root Tips ◽  
Xylem Structure ◽  
Pit Membrane ◽  
Potential Gradients ◽  
Uniform Diameter

To understand water flow in tracheary elements, hydraulic conductances per unit length were measured and then compared with theoretical values calculated from xylem anatomical measurements using the Hagen -Poiseuille relation for nine species of pteridophytes, including Psilotum and eight species of ferns. In ferns the water potential gradients were essentially constant from the root tips to the distal portion of the leaf rachises, although somewhat larger gradients were found from the petiolule onward. Although tracheid number and diameter apparently controlled water flow in xylem, estimates of hydraulic conductance per unit length predicted from tracheid numbers and diameters were generally twice those actually measured from plants under steady-state conditions. A model was developed to account for this discrepancy for Pteris vittata, indicating that pit membrane resistances may contribute 70% of the total resistance to water flow in this fern. This may account for the generally observed deviation of tracheid performance from that predicted for ideal capillaries of uniform diameter.

Research progress in plant hydraulic conductance under different environmental factors

2011 ◽  
Vol 19 (2) ◽  
pp. 456-461 ◽  
Author(s):  
Qi-Liang YANG ◽  
Fu-Cang ZHANG ◽  
Xiao-Gang LIU ◽  
Nan ZHANG ◽  
Zhen-Yang GE
Keyword(s):  
Environmental Factors ◽  
Hydraulic Conductance ◽  
Research Progress

PEACH TREE VIGOR IS A FUNCTION OF ROOTSTOCK XYLEM ANATOMY AND HYDRAULIC CONDUCTANCE

2012 ◽  
pp. 483-489 ◽  
Author(s):  
S. Tombesi ◽  
J. Marsal ◽  
B. Basile ◽  
A. Weibel ◽  
L. Solari ◽  
...  
Keyword(s):  
Hydraulic Conductance ◽  
Peach Tree ◽  
Xylem Anatomy

scholarly journals Ethylene enhances root water transport and aquaporin expression in trembling aspen (Populus tremuloides) exposed to root hypoxia

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Xiangfeng Tan ◽  
Mengmeng Liu ◽  
Ning Du ◽  
Janusz J. Zwiazek
Keyword(s):  
Gas Exchange ◽  
Water Transport ◽  
Populus Tremuloides ◽  
Leaf Gas Exchange ◽  
Hydraulic Conductance ◽  
Root Hydraulic Conductance ◽  
Trembling Aspen ◽  
Expression Levels ◽  
Root Hypoxia ◽  
Exogenous Ethylene

Abstract Background Root hypoxia has detrimental effects on physiological processes and growth in most plants. The effects of hypoxia can be partly alleviated by ethylene. However, the tolerance mechanisms contributing to the ethylene-mediated hypoxia tolerance in plants remain poorly understood. Results In this study, we examined the effects of root hypoxia and exogenous ethylene treatments on leaf gas exchange, root hydraulic conductance, and the expression levels of several aquaporins of the plasma membrane intrinsic protein group (PIP) in trembling aspen (Populus tremuloides) seedlings. Ethylene enhanced net photosynthetic rates, transpiration rates, and root hydraulic conductance in hypoxic plants. Of the two subgroups of PIPs (PIP1 and PIP2), the protein abundance of PIP2s and the transcript abundance of PIP2;4 and PIP2;5 were higher in ethylene-treated trembling aspen roots compared with non-treated roots under hypoxia. The increases in the expression levels of these aquaporins could potentially facilitate root water transport. The enhanced root water transport by ethylene was likely responsible for the increase in leaf gas exchange of the hypoxic plants. Conclusions Exogenous ethylene enhanced root water transport and the expression levels of PIP2;4 and PIP2;5 in hypoxic roots of trembling aspen. The results suggest that ethylene facilitates the aquaporin-mediated water transport in plants exposed to root hypoxia.

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