Evaluation of Resistance of Horticultural Plants to Destabilizing Effects Based on Analysis of Leaf Reflection Spectra

Abstract

The infl uences of thermal effects and salinization on visible and near-IR refl ection spectra of horticultural plant leaves with different drought and salt resistance are examined. An integral criterion for evaluating the susceptibility of the plants to stressors is based on measuring the distance between refl ectance curves.Refl ectance spectroscopy of photosynthetic tissues is one of the most promising non-destructive methods for diagnosing the physiological condition of plants and their resistance to destabilizing effects. Leaves are known to make up the principal refl ecting surface of plants. The refl ectance of a leaf is conditioned by the pigment concentration, tissue structure, water content, and age [1][2][3][4][5][6]. Spectral curves characterizing leaf refl ection coeffi cients (RC) are the integral product of genetic effects and environmental factors [7,8]. The spectral characteristics of visible and IR refl ections can be used to diagnose stress effects, e.g., drought, high temperatures, UV radiation, heavy metals, mineral defi cits, and pests [2,[8][9][10][11][12][13][14][15][16]. However, this method was reported to have limited sensitivity for studying trees because of the considerable variability of the RC depending on the selected photosynthetic organs [17,18]. It was noted [19] that results from many investigations did not achieve the accuracy required for practical use in agriculture.A series of coeffi cients (vegetation indices) calculated from the ratio or difference of RC in certain spectral ranges was proposed to fi nd differences in the refl ectivity of plants [6,[20][21][22][23][24][25][26][27][28]. These coeffi cients are very often associated with pigment content and activity or water content in the plant. Other methods are used to interpret the spectral curves, e.g., calculation of the slope of the electromagnetic spectrum in a certain region [8,29] and subtraction of spectra [30]. Most research was carried out on fi eld or forest cultures. Information on horticultural plants is limited.The present work proposes a spectroscopic model for evaluating the resistance of horticultural plants to drought and salinization that is based on analyses of leaf refl ectance spectra (RS) under varying conditions.The work was performed using the genetic collection at the I. V. Michurin All-Russian Research Institute for Genetics and Breeding of Fruit Plants in 2013-2014. The varieties of horticultural plants used in the work were appeared in the State Registry of Breeding Achievements and included common apricot (Armeniaca vulgaris Lam.), variety Ulyanikhinskii; apple (Malus domestica Borkh.), variety Bylina; plum (Prunus domestica L.), variety Svetlyachok; and black currant (Ribes nigrum L.), variety Ekzotika. The species were selected because of differences in their resistance that were observed in preliminary tests. The plants were cultivated under favorable conditions during the research (July-August) and did not experience destabilizing effects. Undamaged and externally healthy leaves taken fro...

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