Vulnerability to drought‐induced cavitation in poplars: synthesis and future opportunities

Vulnerability to drought‐induced cavitation is a key trait of plant water relations. Here, we summarize the available literature on vulnerability to drought‐induced cavitation in poplars (Populus spp.), a genus of agronomic, ecological and scientific importance. Vulnerability curves and vulnerability parameters (including the water potential inducing 50% loss in hydraulic conductivity, P₅₀) were collected from 37 studies published between 1991 and 2014, covering a range of 10 species and 12 interspecific hybrid crosses. Results of our meta‐analysis confirm that poplars are among the most vulnerable woody species to drought‐induced cavitation (mean P₅₀ = ?1.44 and ?1.55 MPa across pure species and hybrids, respectively). Yet, significant variation occurs among species (P₅₀ range: 1.43 MPa) and among hybrid crosses (P₅₀ range: 1.12 MPa), within species and hybrid crosses (max. P₅₀ range reported: 0.8 MPa) as well as in response to environmental factors including nitrogen fertilization, irradiance, temperature and drought (max. P₅₀ range reported: 0.75 MPa). Potential implications and gaps in knowledge are discussed in the context of poplar cultivation, species adaptation and climate modifications. We suggest that poplars represent a valuable model for studies on drought‐induced cavitation, especially to elucidate the genetic and molecular basis of cavitation resistance in Angiosperms.