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Responses of transpiration and canopy conductance to partial defoliation of Eucalyptus globulus trees


Quentin, AG and O'Grady, AP and Beadle, CL and Worledge, D and Pinkard, EA, Responses of transpiration and canopy conductance to partial defoliation of Eucalyptus globulus trees, Agricultural and Forest Meteorology, 151, (3) pp. 356-364. ISSN 0168-1923 (2011) [Refereed Article]

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DOI: doi:10.1016/j.agrformet.2010.11.008


Partial defoliation has been shown to affect the water relations and transpiration (gas exchange) of plants. Over one growing season, the water relations in response to partial (45%) defoliation were examined in four-year-old Eucalyptus globulus trees in southern Australia. Daily maximum transpiration rates (Emax), maximum canopy conductance (GCmax), and diurnal patterns of tree water-use were measured over a period of 215 days using the heat-pulse technique in adjacent control (non-defoliated) and defoliated trees. Sap-flux measurements were used to estimate canopy conductance and soil-to-leaf hydraulic conductance (KP); leaf water potential () and climate data were also collected. Following the removal of the upper canopy layer, defoliated trees exhibited compensatory responses in transpiration rate and canopy conductance of the remaining foliage. Defoliated E. globulus had similar predawn but higher midday l, transpiration rates (E), canopy conductance (GC) and KP compared to the non-defoliated controls, possibly in response to increased water supply per unit leaf area demonstrated by higher midday l. Higher E in defoliated E. globulus trees was the result of higher GC in the morning and early afternoon. This paper also incorporates the cumulative effect of defoliation, in a phenomenological model of maximum canopy conductance of E. globulus. These results contribute to a mechanistic understanding of plant responses to defoliation, in particular the often observed up-regulation of photosynthesis that also occurs in response to defoliation.

Item Details

Item Type:Refereed Article
Keywords:Transpiration; Canopy conductance; Leaf water potential; Soil-to-leaf hydraulic conductance; Vapour pressure deficit
Research Division:Agricultural, Veterinary and Food Sciences
Research Group:Forestry sciences
Research Field:Tree nutrition and physiology
Objective Division:Plant Production and Plant Primary Products
Objective Group:Forestry
Objective Field:Forestry not elsewhere classified
UTAS Author:Quentin, AG (Dr Audrey Quentin)
UTAS Author:O'Grady, AP (Dr Anthony O'Grady)
UTAS Author:Beadle, CL (Dr Christopher Beadle)
UTAS Author:Worledge, D (Mr Dale Worledge)
UTAS Author:Pinkard, EA (Dr Elizabeth Pinkard)
ID Code:67041
Year Published:2011
Web of Science® Times Cited:42
Deposited By:Agricultural Science
Deposited On:2011-02-23
Last Modified:2012-05-23
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