ISHS Acta Horticulturae 537: III International Symposium on Irrigation of Horticultural Crops
CARBON ISOTOPE DISCRIMINATION AND TRANSPIRATION EFFICIENCY IN EUCALYPTUS UNDER SALINITY AND BORON STRESS |
| Authors: | J.A. Poss, D.L. Suarez, C.M. Grieve, M.C. Shannon, S.R. Grattan |
| Keywords: | Eucalyptus camaldulensis, 13C discrimination, salt stress, salt tolerance |
| Abstract:
We tested the hypothesis that stable carbon-isotopic composition in Eucalyptus trees can be an indicator of the cumulative salinity and boron stress history of the plant. In a controlled, outdoor sand-tank study, Eucalyptus camaldulensis saplings were irrigated with combinations of salinity (EC 2 to 28 dS m-1) and B (1 to 30 mg l-1) to determine their influence on tree growth, water use, and stable carbon-isotope discrimination. Our results indicate carbon-isotope discrimination (D) was primarily reduced by salinity stress, whereas boron effects were smaller in magnitude and significant only at low salinity. Carbon-isotopic discrimination in leaves of Eucalyptus varied with position in the canopy. For example, proximal leaves sampled low in the canopy D decreased from 23.6 ‰ at low salinity (2 dS m-1 and 1 mg l-1 B) to 22.6 ‰ at high salinity (22 dS m-1 and 1 mg l-1 B). In distal leaves sampled high in the canopy, D decreased from 21.1‰ to 19.8‰ in corresponding treatments. Isotopic discrimination in woody tissue from tree trunks also correlated well with salinity stress. Moreover we found the relationship between D and EC of the irrigation water was similar to that of biomass and EC suggesting that D may be useful in describing salt tolerance in as well as quantifying the salt-stress history in C3 trees. There was a significant relationship between isotope discrimination in leaf and wood tissue with transpiration efficiency. The relationship was position sensitive for leaves and correlations with wood tissue increased with time under stress. | |
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