title: HyperART: non-invasive quantification of leaf traits using hyperspectral absorption-reflectance-transmittance imaging.
abstract: BACKGROUND
  Combined assessment of leaf reflectance and transmittance is currently limited to spot (point) measurements. This study introduces a tailor-made hyperspectral absorption-reflectance-transmittance imaging (HyperART) system, yielding a non-invasive determination of both reflectance and transmittance of the whole leaf. We addressed its applicability for analysing plant traits, i.e. assessing Cercospora beticola disease severity or leaf chlorophyll content. To test the accuracy of the obtained data, these were compared with reflectance and transmittance measurements of selected leaves acquired by the point spectroradiometer ASD FieldSpec, equipped with the FluoWat device.
  
  
  RESULTS
  The working principle of the HyperART system relies on the upward redirection of transmitted and reflected light (range of 400 to 2500 nm) of a plant sample towards two line scanners. By using both the reflectance and transmittance image, an image of leaf absorption can be calculated. The comparison with the dynamically high-resolution ASD FieldSpec data showed good correlation, underlying the accuracy of the HyperART system. Our experiments showed that variation in both leaf chlorophyll content of four different crop species, due to different fertilization regimes during growth, and fungal symptoms on sugar beet leaves could be accurately estimated and monitored. The use of leaf reflectance and transmittance, as well as their sum (by which the non-absorbed radiation is calculated) obtained by the HyperART system gave considerably improved results in classification of Cercospora leaf spot disease and determination of chlorophyll content.
  
  
  CONCLUSIONS
  The HyperART system offers the possibility for non-invasive and accurate mapping of leaf transmittance and absorption, significantly expanding the applicability of reflectance, based on mapping spectroscopy, in plant sciences. Therefore, the HyperART system may be readily employed for non-invasive determination of the spatio-temporal dynamics of various plant properties.
authors: Institute for Bio- and Geosciences, IBG-2: Plant Sciences, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany.
authors: Sergej
authors: S
authors: Bergsträsser
authors: Institute for Bio- and Geosciences, IBG-2: Plant Sciences, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany ; Present address: Department of Crop Science, Technological Educational Institute of Crete, GR 71004 Heraklio, Greece ; Present address: Institute of Viticulture, Floriculture and Vegetable Crops, Hellenic Agricultural Organization 'Demeter' (NAGREF), P.O. Box 2228, GR 71003 Heraklio, Greece.
authors: Dimitrios
authors: D
authors: Fanourakis
authors: Institute for Bio- and Geosciences, IBG-2: Plant Sciences, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany.
authors: Simone
authors: S
authors: Schmittgen
authors: Institute for Bio- and Geosciences, IBG-2: Plant Sciences, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany.
authors: Maria Pilar
authors: MP
authors: Cendrero-Mateo
authors: Institute for Bio- and Geosciences, IBG-2: Plant Sciences, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany ; Present address: LemnaTec GmbH, Pascalstraße 59, 52076 Aachen, Germany.
authors: Marcus
authors: M
authors: Jansen
authors: Institute for Bio- and Geosciences, IBG-2: Plant Sciences, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany.
authors: Hanno
authors: H
authors: Scharr
authors: Institute for Bio- and Geosciences, IBG-2: Plant Sciences, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany.
authors: Uwe
authors: U
authors: Rascher
keywords: Absorption; Cercospora beticola; Chlorophyll content; FieldSpec; FluoWat; Hyperspectral imaging; Imaging spectroscopy; Non-invasive phenotyping; Reflectance; Transmittance
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