TopPlant, Cell & Environment Virtual Special Issue Library

Table of Contents

Dynamics of water transport and storage in conifers studied with deuterium and heat tracing techniques
Meinzer, FC; Brooks, JR; Domec, JC; Gartner, BL; Warren, JM; Woodruff, DR; Bible, K; Shaw, DC
Volume 29, Issue 1, Page 105-114 January 2006
Injection of deuterated water (D₂O) into stems of Pseudotsuga menziesii and Tsuga heterophylla demonstrated that tracer residence time increased linearly with stem diameter, while tracer velocity scaled with sapwood conductivity (Ks). When combined with data from a range of angiosperm species, species-independent scaling relationships were obtained between sapwood capacitance and both tracer residence time and tracer velocity, suggesting an important role for sapwood capacitance in whole-tree water relations. 

Sap salinity effects on xylem conductivity in two mangrove species
Lopez-Portillo, J; Ewers, FW; Angeles, G
Volume 28, Issue 10, Page 1285-1292 October 2005
Xylem sap ionic concentration in the range measured in the sap of two mangrove species has significant effects on xylem hydraulic conductivity, with maximum values achieved at intermediate concentrations. 

Axial and radial profiles in conductivities, water storage and native embolism in trunks of young and old-growth ponderosa pine trees
Domec, JC; Pruyn, ML; Gartner, BL
Volume 28, Issue 9, Page 1103-1113, September 2005
The xylem of young ponderosa pine trees is less conductive (lower Ks) than in the trunks of old-growth trees, but also exhibits lower PLC. At the top of the old-growth trees, xylem properties were similar, both the degree of embolism and capacitance were lower than in young trees of similar cambial age. 

Hydraulic design of pine needles: one-dimensional optimization for single-vein leaves
Zwieniecki, MA; Stone, HA; Leigh, A; Boyce, CK; Holbrook, NM
Volume 29, Issue 5, Page 803-809, May 2006
The distribution of hydraulic permeability in pine needle veins maximizes needle length for a given pressure difference between petiole and leaf tip. The good agreement between observed and optimal distribution of transport capacity indicates that vein structure plays a significant role in the hydraulic design of leaves. 

Freeze/thaw-induced embolism depends on nadir temperature: the heterogeneous hydration hypothesis
Ball, MC; Canny, MJ; Huang, CX; Egerton, JJG; Wolfe, J
Volume 29, Issue 5, Page 729-745, May 2006
The greater freeze/thaw-induced embolism observed in leaves frozen to -6 versus -3 °C corresponded with the formation of larger volumes of extracellular ice within the midvein. Cavitaiton upon thawing is hypothesized to result not from the distillation of bubbles from the xylem sap but rather from tensions resulting from the dehydration of cell walls due to the freeze-induced redistribution of water within the leaf. 

The spatial pattern of air seeding thresholds in mature sugar maple trees
Choat, B; Lahr, EC; Melcher, PJ; Zwieniecki, MA; Holbrook, NM
Volume 28, Issue 9, Page 1082-1089, September 2005
Air-seeding thresholds, measured in individual xylem vessels in the current year's growth along the entire length of a mature sugar maple tree, indicated significantly more vulnerable conduits in roots and in leaves. Within the stem, there was little variation in air-seeding thresholds despite significant variation in conduit diameter. Primary xylem conduits, however, had lower thresholds and likely make an important contribution to the lower values observed in petioles and leaves. 

MRI of long distance water transport: a comparison of the phloem and xylem flow characteristics and dynamics in poplar, castor bean, tomato and tobacco
Henk Van As
Volume 29, Issue 9, Page 1715, September 2006
Magnetic resonance imaging of phloem transport illustrates both variation among species in the fraction of xylem water recycled for phloem transport (Munch counter flow), and relative uniformity in phloem flux rates. The latter suggests that phloem flow velocity may be constrained by both sieve tube integrity and the role of the phloem as a conduit for information transfer. 

Mechanical reinforcement of tracheids compromises the hydraulic efficiency of conifer xylem
Jarmila Pittermann
Volume 29, Issue 8, Page 1618, August 2006
A conflict between strength and efficiency of conifer tracheids results from the fact that mechanical reinforcement was primarily due to reductions in tracheid diameter rather than increases in wall thickness. In Pinaceae and Cupressaceae, mechanical reinforcement correlated strongly with resistance to drought-induced embolism. 

Inter-vessel pitting and cavitation in woody Rosaceae and other vesselled plants: a basis for a safety versus efficiency trade-off in xylem transport
Wheeler, JK; Sperry, JS; Hacke, UG; Hoang, N
Volume 28, Issue 6, Page 800-812, June 2005
The surprising lack of a relationship between pit membrane porosity and cavitation resistance, but an inverse relationship between pit area per vessel and vulnerability, suggests that the basis for the safety/efficiency trade-off lies in the degree to which vessels are interconnected, rather than the structure of the pit membranes themselves. 

Circadian regulation of leaf hydraulic conductance in sunflower (Helianthus annuus L. cv Margot)
Nardini, A; Salleo, S; Andri, S
Volume 28, Issue 6, Page 750-759 June 2005
Circadian variation in leaf hydraulic conductance persists under constant illumination, can be shifted over a period of days when photoperiod is inverted, eliminated by short-circuiting water flow to the mesophyll by severing fine veins, and is reversibly modulated by application of mercurials. These data underscore the important physiological control of leaf hydraulic conductance, possibly mediated by aquaporins. 

Comparative analysis of end wall resistivity in xylem conduits
Sperry, JS; Hacke, UG; Wheeler, JK
Volume 28, Issue 4, Page 456-465, April 2005
Analysis of vessel networks indicates that lumen and end wall resistivities are approximately co-limiting. End wall resistance was inversely proportional to conduit length, consistent with their having more end wall pits. 

Ion-mediated increase in the hydraulic conductivity of Laurel stems: role of pits and consequences for the impact of cavitation on water transport
Nardini, A; Salleo, S
Volume 29, Issue 10, Page 1946, October 2006
The effect of xylem sap cation concentrations on xylem hydraulic conductivity was shown to increase with both the length of the measured sampled and the degree of cavitation. PLC measured with KCL solution was significantly less than when measured with water, which has implications for both the measurement of PLC and the ways in which plants might compensate hydraulically for losses due to cavitation.