Detection of physiological traits and reflectance indices in Olea europaea L. saplings subject to the interaction of water stress and nitrogen availability

The relation of reflectance indices to leaf gas exchange, optical based indices related to leaf nitrogen (NBI) and chlorophyll (Chl) content parameters were studied in olive (Olea europaea) saplings subjected to the interaction of nitrogen availability and water stress. Water deficit significantly affected leaf water potential (?l), photosynthesis (A) and stomatal conductance (gs). These parameters were also significantly reduced by nitrogen deprivation in well-watered olive plants. All physiological parameters fully recovered five days after re-watering (RW). Dualex measurements of leaf N content showed a significant difference between the two fertilization treatments. Leaf reflectance indices were compared to physiological and water status parameters. Strong correlations were observed between the photochemical reflectance index with both A and gs. The relative depth index was also positively correlated with both gs and ?l. Differences in nitrogen content were detected by the NRI index. Our study confirms that variations in the physiological status of olive trees can be accurately detected remotely; therefore, non-invasive sensing technologies can be successfully used to assess plant water and nutritional status, thus enabling effective crop management.