A tracheomycosis as a tool for studying the impact of stem xylem dysfunction on leaf water status and gas exchange in Citrus aurantium L.
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Permanent xylem blockage is a common result of attacks by herbivores and fungi. The mitosporic fungus Phoma tracheiphila (Petri) Kantschaveli et Gikachvili, is the agent of a Citrus tracheomycosis (“malsecco disease”) causing xylem impairment and leading to leaf shedding and plant dieback. In the present study, this pathogen was used for monitoring the effects of increasing levels of stem hydraulic resistance (R stem) on leaf water status and gas exchange. In this view, measurements are reported of changes in the hydraulic resistance of infected stems (R stem) of C. aurantium (sour orange) during progressive and irreversible xylem blockage with parallel measurements of leaf water potential and conductance to water vapour. Leaves were highly responsive to increasing R stem as due to fungal infection, with substantial stomatal closure and drop in water potential.
KeywordsStem hydraulic resistance Leaf gas exchange Leaf water status Xylem blockage P. thacheiphila
We thank Professor G. Magnano di San Lio for giving us Phoma tracheiphila conidia from his cultures as well as for helpful suggestions and stimulating discussions.
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