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Co-ordination of growth, gas exchange and hydraulics define the carbon safety margin in tree species with contrasting drought strategies


Mitchell, PJ and O'Grady, AP and Tissue, DT and Worledge, D and Pinkard, EA, Co-ordination of growth, gas exchange and hydraulics define the carbon safety margin in tree species with contrasting drought strategies, Tree Physiology, 34, (5) pp. 443-458. ISSN 0829-318X (2014) [Refereed Article]

Copyright Statement

The Author 2014.

DOI: doi:10.1093/treephys/tpu014


Gas exchange, growth, water transport and carbon (C) metabolism diminish during drought according to their respective sensitivities to declining water status. The timing of this sequence of declining physiological functions may determine how water and C relations compromise plant survival. In this paper, we test the hypothesis that the degree of asynchrony between declining C supply (photosynthesis) and C demand (growth and respiration) determines the rate and magnitude of changes in whole-plant non-structural carbohydrates (NSC) during drought. Two complementary experiments using two tree species (Eucalyptus globulus Labill. and Pinus radiata D. Don) with contrasting drought response strategies were performed to (i) assess changes in radial stem growth, transpiration, leaf water potential and gas exchange in response to chronic drought, and (ii) evaluate the concomitant impacts of these drought responses on the temporal patterns of NSC during terminal drought. The three distinct phases of water stress were delineated by thresholds of growth cessation and stomatal closure that defined the 'carbon safety margin' (i.e., the difference between leaf water potential when growth is zero and leaf water potential when net photosynthesis is zero). A wider C safety margin in E. globulus was defined by an earlier cessation of growth relative to photosynthesis that reduced the demand for NSC while maintaining C acquisition. By contrast, the narrower C safety margin in P. radiata was characterized by a synchronous decline in growth and photosynthesis, whereby growth continued under a declining supply of NSC from photosynthesis. The narrower C safety margin in P. radiata was associated with declines in starch concentrations after ~90 days of chronic drought and significant depletion of starch in all organs at mortality. The observed divergence in the sensitivity of drought responses is indicative of a potential trade-off between maintaining hydraulic safety and adequate C availability.

Item Details

Item Type:Refereed Article
Keywords:drought mortality, growth, non-structural carbohydrates, plant strategy, stomatal regulation, water deficit
Research Division:Biological Sciences
Research Group:Plant biology
Research Field:Plant physiology
Objective Division:Plant Production and Plant Primary Products
Objective Group:Forestry
Objective Field:Forestry not elsewhere classified
UTAS Author:Mitchell, PJ (Dr Patrick Mitchell)
UTAS Author:O'Grady, AP (Dr Anthony O'Grady)
ID Code:119547
Year Published:2014
Web of Science® Times Cited:88
Deposited By:Plant Science
Deposited On:2017-08-02
Last Modified:2017-09-11

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