Hyperspectral assessment of physiological and morphological leaf traits related with drought in three varieties of Aucuba japonica with different leaf variegation

Advancements in techniques to assess plant status are needed for nursery management. Hyperspectral data have great potential to rapidly and non-destructively monitor plant stress. However, this method has been exclusively developed on green leaf species, although plants with variegated foliage are a prerogative of nurserymen, because of their aesthetic peculiarity. This study examined the capability of reflectance spectroscopy (400-2400 nm) to characterize responses to water deprivation of three varieties of Aucuba japonica with no, mild and high leaf variegation. Partial least squares regression models were built to predict from spectra an array of leaf photosynthetic, water and morphological traits related with drought. Predictive models for photosynthetic traits were not accurate (R2: 0.10-0.58), whereas those for water and morphological ones showed an excellent prediction accuracy (R2: 0.65-0.94), this because only these latter models did not include the visible spectral region (400-700 nm) which is highly susceptible to leaf variegation. Variations of spectral indices and spectra-derived traits confirmed A. japonica as drought tolerant, especially the not variegated variety.