Evaporative flux method of leaf hydraulic conductance estimation: sources of uncertainty and reporting format recommendation

Abstract

Background: The accurate estimation of leaf hydraulic conductance (Kleaf) is important for revealing leaf physiological characteristics and function. However, the Kleaf values are largely incomparable in previous studies for a given species indicating some uncertain influencing factors in Kleaf measurement. Result: We investigated the potential impacts of plant sampling method, measurement setup, environmental factors, and transpiration steady state identification on Kleaf estimation in Oryza sativa and Cinnamomum camphora using evaporation flux method (EFM). The effects of sampling and rehydration time, the small gravity pressure gradients between water sources and leaves, and water degassing on Kleaf estimation were negligible. As expected, the estimated steady flow rate (E) was significantly affected by multiple environmental factors including airflow around leaf, photosynthetically active radiation (PARa) on leaf surfaces and air temperature. Kleaf decreased by 40% when PARa declined from 1000 to 500 µmol m−2 s−1 and decreased by 15.1% when air temperature increased from 27 to 37 °C. In addition, accurate steady-state flow rate identification and leaf water potential measurement were important for Kleaf estimation. Conclusions: Based on the analysis of influencing factors, we provided a format for reporting the metadata of EFM-based Kleaf to achieve greater comparability among studies and interpretation of differences.