Salix nigra, black willow, is used for wetland restoration and streambank stabilization and like other wetland species has the ability to develop aerenchyma tissue to avoid root anoxia. Root aerenchyma development could be affected if the temperature of the rhizosphere increases as a result of climatic change. Root porosity (used as an indication of aerenchyma tissue) of S. nigracuttings grown under three soil temperature regimes was found to increase in response to increases in temperature (F2,40 = 56.57; p < 0.0001). There was also an increase in internal C (carbon) concentration (F2,27 = 27.36; P < 0.0001) and a corresponding decrease in stomatal conductance (F2,27 = 3.728; P = 0.037), transpiration rate (F2,27 = 5.084; P = 0.013), and net photosynthesis (F2,27 = 14.07; P < 0.0001) in response to increased soil temperature. The present research demonstrated that the stress response of S. nigra to increased soil temperature is similar to its response to anoxic conditions.
Key words: Aerenchyma, global warming, Salix nigra, remediation, rhizospere, riparian systems.
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