Journal Article

Leaf hydraulic conductance, measured in situ, declines and recovers daily: leaf hydraulics, water potential and stomatal conductance in four temperate and three tropical tree species

D.M. Johnson, D.R. Woodruff, K.A. McCulloh and F.C. Meinzer

in Tree Physiology

Volume 29, issue 7, pages 879-887
Published in print July 2009 | ISSN: 0829-318X
Published online July 2009 | e-ISSN: 1758-4469 | DOI: http://dx.doi.org/10.1093/treephys/tpp031
Leaf hydraulic conductance, measured in situ, declines and recovers daily: leaf hydraulics, water potential and stomatal conductance in four temperate and three tropical tree species

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Adequate leaf hydraulic conductance (K leaf) is critical for preventing transpiration-induced desiccation and subsequent stomatal closure that would restrict carbon gain. A few studies have reported midday depression of K leaf (or petiole conductivity) and its subsequent recovery in situ, but the extent to which this phenomenon is universal is not known. The objectives of this study were to measure K leaf, using a rehydration kinetics method, (1) in the laboratory (under controlled conditions) across a range of water potentials to construct vulnerability curves (VC) and (2) over the course of the day in the field along with leaf water potential and stomatal conductance (g s). Two broadleaf (one evergreen, Arbutus menziesii Pursh., and one deciduous, Quercus garryana Dougl.) and two coniferous species (Pinus ponderosa Dougl. and Pseudotsuga menziesii [Mirbel]) were chosen as representative of different plant types. In addition, K leaf in the laboratory and leaf water potential in the field were measured for three tropical evergreen species (Protium panamense (Rose), Tachigalia versicolor Standley and L.O. Williams and Vochysia ferruginea Mart) to predict their daily changes in field K leaf in situ. It was hypothesized that in the field, leaves would close their stomata at water potential thresholds at which K leaf begins to decline sharply in laboratory-generated VC, thus preventing substantial losses of K leaf. The temperate species showed a 15–66% decline in K leaf by midday, before stomatal closure. Although there were substantial midday declines in K leaf, recovery was nearly complete by late afternoon. Stomatal conductance began to decrease in Pseudotsuga, Pinus and Quercus once K leaf began to decline; however, there was no detectable reduction in g s in Arbutus. Predicted K leaf in the tropical species, based on laboratory-generated VC, decreased by 74% of maximum K leaf in Tachigalia, but only 22–32% in Vochysia and Protium. The results presented here, from the previous work of the authors and from other published studies, were consistent with two different strategies regarding daily maintenance of K leaf: (1) substantial loss and subsequent recovery or (2) a more conservative strategy of loss avoidance.

Keywords: cavitation; embolism; photosynthesis; transpiration; xylem

Journal Article.  5836 words.  Illustrated.

Subjects: Plant Sciences and Forestry

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