Factors that affect measurement using the WP4C dewpoint potential meter to determine water potential——Illustrated by the case of Dalbergia odorifera

The main factors that affect the determination of plant water potential are leaf sizes, shapes, fragmentation degree, sampling time, and sample storage; however, relative studies are very limited. In the present research, Dalbergia odorifera T. Chen individuals with similar maturity and strong pinnately compound leaves were used to study the above mentioned factors. The diurnal dynamic changes in leaf water potential were measured with the WP4C dewpoint potential meter every hour. Results showed that the most reasonable period for determination of leaf water potential was from 09:00 to 13:00. The leaf water potentials of leaves stored at 4℃ for 0, 0.5, 1, 2, and 3 h were measured, respectively. Results suggested that the best storage duration to measure leaf water potential was within 1 h after sampling. Our results also showed that leaf shapes, sizes, and fragmentation degrees had significant influences on water potential. Single leaf samples should completely cover the sample chamber of the instrument when leaf water potential is determined. Under our optimized conditions, the methods exhibited high accuracy, repeatability, and stability.