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Interactive effects of water supply and defoliation on photosynthesis, plant water status and growth of Eucalyptus globulus Labill


Quentin, AG and O'Grady, AP and Beadle, CL and Mohammed, C and Pinkard, EA, Interactive effects of water supply and defoliation on photosynthesis, plant water status and growth of Eucalyptus globulus Labill, Tree Physiology, 32, (8) pp. 958-967. ISSN 0829-318X (2012) [Refereed Article]

Copyright Statement

Copyright 2012 The Authors.

DOI: doi:10.1093/treephys/tps066


Increased climatic variability, including extended periods of drought stress, may compromise on the health of forest ecosystems. The effects of defoliating pests on plantations may also impact on forest productivity. Interactions between climate signals and pest activity are poorly understood. In this study, we examined the combined effects of reduced water availability and defoliation on maximum photosynthetic rate (Asat), stomatal conductance (gs), plant water status and growth of Eucalyptus globulus Labill. Field-grown plants were subjected to two water-availability regimes, rain-fed (W−) and irrigated (W+). In the summer of the second year of growth, leaves from 75% of crown length removed from trees in both watering treatments and physiological responses within the canopies were examined. We hypothesized that defoliation would result in improved plant water status providing a mechanistic insight into leaf- and canopy-scale gas-exchange responses. Defoliated trees in the W+ treatment exhibited higher Asat and gs compared with non-defoliated trees, but these responses were not observed in the W− treatment. In contrast, at the whole-plant scale, maximum rates of transpiration (Emax) and canopy conductance (GCmax) and soil-to-leaf hydraulic conductance (KP) increased in both treatments following defoliation. As a result, plant water status was unaffected by defoliation and trees in the defoliated treatments exhibited homeostasis in this respect. Whole-plant soil-to-leaf hydraulic conductance was strongly correlated with leaf scale gs and Asat following the defoliation, providing a mechanistic insight into compensatory up-regulation of photosynthesis. Above-ground height and diameter growth were unaffected by defoliation in both water availability treatments, suggesting that plants use a range of responses to compensate for the impacts of defoliation.

Item Details

Item Type:Refereed Article
Keywords:compensatory response, leaf and canopy stomatal conductance, maximum leaf photosynthetic rate, soil-to-leaf hydraulic conductance, transpiration
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:Mohammed, C (Professor Caroline Mohammed)
ID Code:67045
Year Published:2012
Deposited By:Research Division
Deposited On:2011-02-23
Last Modified:2017-11-09

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