Interactive effects of xylem and phloem damage under drought on plant water and carbon dynamics: Mimicking the impact of plant canker disease

O_LIIt is often stated that trees experiencing climate change may be more vulnerable to damaging effects of pest and disease, but experimental tests are still rare. In this study, we examined the separate and combined impact of experimentally applied xylem and phloem damage in an Australian Eucalypt species (Corymbia calophylla), which is increasingly suffering from phloem and xylem damage by a canker disease caused by Quambalaria coyrecup. C_LIO_LICut treatments were applied to saplings under controlled conditions by removing xylem only ([~]56%), phloem only ([~]70%) or both in the main stem under well-watered and drought treatments. C_LIO_LIAs expected, xylem damage reduced whole-plant conductance, stomatal conductance and photosynthesis, and hence growth. Phloem damage limited phloem transport, increased leaf non-structural carbohydrate concentrations (NSC), and reduced root NSC, photosynthesis and growth. Contrary to expectations, effects were larger in well-watered than droughted plants. The combined effects of damage to xylem and phloem were generally less than additive. Plants were remarkably resilient to significant loss of xylem and phloem, although xylem damage had a greater impact on most of the physiological parameters than phloem damage. C_LIO_LIThese results reveal potential consequences of xylem-phloem dysfunction due to biotic attack, leading to whole tree mortality, in association with drought stress. C_LI