Working Paper Article Version 2 This version is not peer-reviewed

Linking Tissue Damage to Hyperspectral Reflectance for Non-Invasive Monitoring of Apple Fruit in Orchards

Version 1 : Received: 16 December 2020 / Approved: 17 December 2020 / Online: 17 December 2020 (16:08:39 CET)
Version 2 : Received: 2 February 2021 / Approved: 2 February 2021 / Online: 2 February 2021 (12:58:42 CET)

How to cite: Solovchenko, A.; Dorokhov, A.; Shurygin, B.; Nikolenko, A.; Velichko, V.; Smirnov, I.; Khort, D.; Aksenov, A.; Kuzin, A. Linking Tissue Damage to Hyperspectral Reflectance for Non-Invasive Monitoring of Apple Fruit in Orchards. Preprints 2020, 2020120438 Solovchenko, A.; Dorokhov, A.; Shurygin, B.; Nikolenko, A.; Velichko, V.; Smirnov, I.; Khort, D.; Aksenov, A.; Kuzin, A. Linking Tissue Damage to Hyperspectral Reflectance for Non-Invasive Monitoring of Apple Fruit in Orchards. Preprints 2020, 2020120438

Abstract

Reflected light carries ample information about biochemical composition, tissue architecture, and physiological condition of plants. Recent technical progress brought about affordable imaging hyperspectrometers (IH) providing spatially resolved spectral data on plants. The extraction of sensible information from hyperspectral reflectance images is difficult due to inherent complexity of plant tissue and canopy optics, especially when recorded by IH under ambient sunlight. We aimed at obtaining a deeper insight into plant optics as perceived by IH since there is a high demand for algorithms for fruit harvesting and grading systems equipped with computer vision and robotic systems capable of working in orchard. We report on the characteristic changes in hyperspectral reflectance accompanying the accumulation of anthocyanins in healthy fruit, pigment breakdown during sunscald and phytopathogen attacks. The measurements made outdoors with a snapshot IH were compared with traditional “point” reflectance measured with a conventional spectrophotometer under controlled illumination conditions. Most of the spectral features and patterns of plant reflectance were evident in the IH-derived reflectance images. As a step forward, a novel index for highlighting tissue damages on the background of the anthocyanin absorption, BRI-M = (1/Rorange – 1/Rred + 1/RNIR), is suggested. Difficulties of the interpretation of fruit hyperspectral reflectance images recorded in situ are discussed with possible implications for plant physiology and precision horticulture practices.

Keywords

reflectance; hyperspectral imaging; pigments; damages; apple fruit

Comments (1)

Comment 1
Received: 2 February 2021
Commenter: Alexei Solovchenko
Commenter's Conflict of Interests: Author
Comment: This is a revision according to the recommendations of the reviewers as of February 02, 2021
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