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

The accurate estimation of leaf hydraulic conductance (K_leaf) is important for revealing leaf physiological characteristics and function. However, the K_leaf values are largely incomparable in previous studies for a given species indicating some uncertain influencing factors in K_leaf measurement.

We investigated the potential impacts of plant sampling method, measurement setup, environmental factors, and transpiration steady state identification on K_leaf 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 K_leaf 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. K_leaf 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 K_leaf estimation.

Based on the analysis of influencing factors, we provided a format for reporting the metadata of EFM-based K_leaf to achieve greater comparability among studies and interpretation of differences.