MONITORING WATER POTENTIAL AND RELATIVE WATER CONTENT IN EUCALYPTUS CAMALDULENSIS USING NEAR INFRARED SPECTROSCOPY

A genetically diverse cohort of Eucalyptus camaldulensis seedlings were grown under a range of irrigation treatments to impose a range of states of water stress. Near infrared (NIR) spectra obtained from leaf surfaces of these seedlings were calibrated against physiological measurements commonly associated with plant water stress, i.e. relative water content and midday leaf water potential. Spectral data were obtained from upper (adaxial) leaf surfaces of upper and lower leaves on the stem. A strong coefficient of determination of R²p = 0.78 was obtained for the validation set using the calibration developed for midday leaf water potential from the seedling leaf data. However, that for relative water content was relatively low: R²p = 0.41. These results indicated that portable NIR has the potential to provide for rapid, non-destructive assessment of the leaf water potential in E. camaldulensis seedlings.