Abstract: [Objective] [Objective] The aim of this study was to monitor the leaf relative water content (RWC) and water potential (Ψ_w) in structured Eucalyptus camaldulensis and E. tereticornis populations by Near Infrared spectroscopy (NIRS). [Method]The samples were collected from the breeding population, which contained 21 families of 7 provenances for E. camaldulensis, and 26 families of 5 provenances for E. tereticornis. A total of 20 average-growth seedlings per family were chosen, divided into 5 groups randomly, and were watered every day by replenishing 100%, 70%, 50%, 30% and 0% of the average water loss of these seedlings from pots by evapotranspiration, respectively. In 60 days after water controls, three seedlings per water control and per family were chosen, of which the top second pair fully expanded leaves were used to be scanned with a portable near infrared spectrometer for getting the NIRS spectra. After the scanning, the leaf RWC and leaf Ψ_wwere measured. The measurements were conducted once a day for consecutive 18 days.[Result] The results showed that there was a close relationship between water status traits and the raw NIRS at 1 860-1 960 nm. However, after the transform of the 2^nd derivate preprocess for raw NIR spectra, there were significant differences of leaf RWC and Ψ_w among all samples in the whole range of NIRs. The NIRs calibrated PLS(partial least squares) model for the prediction of leaf RWC and Ψ_w both showed a good fitting. The correlation coefficient between predicted and measured value (R²) were 0.92 and 0.84 for leaf Ψ_w and RWC, respectively. The average differences between predicted and measured values (RMSE) were 0.25 and 1.31 for leaf Ψ_w and RWC, respectively. [Conclusion] The coefficient of variation curve showed that the information of whole NIRS range should be used to calibrate the PLS model for the water status traits associated physiological characters in Eucalyptus. All the findings in this study highlight the advantages and perspectives of NIRS in monitoring leaf water status traits in structured Eucalyptus populations.

Key words: Eucalyptus, NIRS, leaf relative water content, leaf water potential, NIRS calibrated PLS model