Relations of sugar composition and δ13C in phloem sap to growth and physiological performance of Eucalyptus globulus (Labill) |
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| Authors: | ANDREW MERCHANT MICHAEL TAUSZ CLAUDIA KEITEL MARK A ADAMS |
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| Institution: | 1. Faculty of Agriculture, Food and Natural Resources, University of Sydney, Sydney, NSW 2006, and;2. Department of Forest and Ecosystem Science, Melbourne School of Land and Environment, University of Melbourne, Creswick, Vic. 3363, Australia |
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| Abstract: | We characterized differences in carbon isotopic content (δ13C) and sugar concentrations in phloem exudates from Eucalyptus globulus (Labill) plantations across a rainfall gradient in south‐western Australia. Phloem sap δ13C and sugar concentrations varied with season and annual rainfall. Annual bole growth was negatively related to phloem sap δ13C during summer, suggesting a water limitation, yet was positively related in winter. We conclude that when water is abundant, variations in carboxylation rates become significant to overall growth. Concentrations of sucrose in phloem sap varied across sites by up to 600 mm, and raffinose by 300 mm . These compounds play significant roles in maintaining osmotic balance and facilitating carbon movement into the phloem, and their relative abundances contribute strongly to overall δ13C of phloem sap. Taken together, the δ13C and concentrations of specific sugars in phloem sap provide significant insights to functions supporting growth at the tree, site and landscape scale. |
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| Keywords: | Eucalyptus carbon isotopes phloem water deficit |
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