Pacific Northwest Research Station

Title: Leaf xylem embolism, detected acoustically and by cryo-SEM, corresponds to decreases in leaf hydraulic conductance in four evergreen species

Author: Johnson, Daniel M.; Meinzer, Frederick C.; Woodruff, David R.; McCulloh, Katherine A.

Date: 2009

Source: Plant, Cell and Environment DOI: 10.1111/j.1365-3040.2009.01961.x

Description: 

Hydraulic conductance of leaves (K_leaf) typically decreases with increasing water stress. However, the extent to which the decrease in K_leaf is due to xylem cavitation, conduit deformation, or changes in the extra-xylary pathway is unclear, We measured K_leaf concurrently with ultrasonic acoustic emission (UAE) in dehydrating leaves of two vessel-bearing and two tracheid-bearlng species to determine whether declining K_leaf was associated with an accumulation of cavitation events. In addition, images of leaf internal structure were captured using cryo-scanning electron microscopy, which allowed detection of empty versus full and also deformed conduits. Decreases in K_leaf were closely associated with accumulated UAE and the percentage of empty conduits. The mean amplitude of UAEs was tightly correlated with mean conduit diameter (R² = 0.94, P = 0.018). These results suggest that water stress-induced decreases in K_leaf in these species are directly related to xylem embolism.

Keywords: cavitation, drought stress, transpiration, water potential

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Citation

Johnson, Daniel M.; Meinzer, Frederick C.; Woodruff, David R.; McCulloh, Katherine A.  2009.  Leaf xylem embolism, detected acoustically and by cryo-SEM, corresponds to decreases in leaf hydraulic conductance in four evergreen species.   Plant, Cell and Environment DOI: 10.1111/j.1365-3040.2009.01961.x.