Comparison of pressure chamber and psychrometer estimates of leaf water potential in rice

Summary The need to compare pressure-chamber estimates of leaf water potential with a psychrometric method has been established for several crop species. We investigated this relationship for rice (Oryza sativa L.) as well as the need to protect leaves from water loss during sampling and measuring period in the pressure chamber. Two rice cultivars grown in containers on a clay-loam soil were stressed to varying degrees by withholding water. Fully expanded leaves were sampled for estimation of leaf water potential by the dew point hygrometer and pressure-chamber techniques. The same leaf was used in both methods allowing direct comparison. Additionally, two alternative methods of leaf handling for measurement by the pressure chamber technique were compared. Protection of leaf samples against water loss during excision, transport and handling was found to be more important at higher leaf water potentials (>−1.0 MPa). The two cultivars used appeared to differ in their response to protection of the leaf sample. These results serve to further caution pressure chamber users on extrapolating comparisons between the two measurement methods and between tissue handling techniques even within a crop species.