Spectral parameters of Robinia pseudoacacia L. seeds in technogenic conditions of urban environment

Abstract

Robinia pseudoacacia L. (black locust) is an invasive species with high activity in alien flora of Ukraine. Invasive potential of plants in unfavorable ecological conditions is due to the presence of adaptive mechanisms. One of the criteria for the invasive potential of foreign plants is considered to be seed productivity. For plants of black locust note a high level of seed productivity. However, it remains to be seen what factors ensure the formation of viable seeds in extreme environments. Among the factors that ensure the formation of viable plant seeds, note the barrier function of the seed coat relative to biotic and abiotic environmental factors. The physiological role of this protective barrier is realized due to the specific properties and component composition of the surface tissues of seeds. Among the metabolites with protective properties localized in the seed coat, consider proanthocyanidins (condensed tannins), which are formed during the biosynthesis of phenolic compounds. To objectively assess changes in the accumulation of proanthocyanidins in the seed coat, it is necessary to use non-destructive methods, because the isolation of these compounds destroys their native polymer structure. The influence of technogenic pollution of Dnipro city on the reflectance, colorimetric and fluorescent characteristics of Robinia pseudoacacia L. seeds is investigated in the work. Mature seeds of black locust were collected at monitoring sites in the Botanical Garden of Oles Honchar Dnipro National University (ecologically favorable zone) and at some points of linear roadside plantations of one of the main highways. It was found that the chronic effect of aerogenic pollutants on black locust plants caused an increased accumulation of proanthocyanidins in the seed coat, which may be due to changes in the biosynthesis of these compounds at the stage of oxidative polymerization of flavonoid subunits. Markers of this reaction of plants are the change of position and increase of intensity of maxima in the reflectance spectra of visible region, increase of value of dominant wavelength, decrease of conditional purity of color tone and colorimetric coefficients, increase of intensity of maxima in seed fluorescence spectra. The protective effect of these adaptive changes is associated with the strengthening of the barrier function of the seed coat to adverse environmental factors to maintain the viability of the seeds under the negative impact of technogenic pollution.