Parectopa robiniella (Lepidoptera, Gracillariidae) influence on key parameters of Robinia pseudoacacia photosynthetic function implementation in different environmental conditions

Abstract

Robinia pseudoacacia L., a representative species of the North American dendroflora and introducent in the dendroflora of the steppe zone of Ukraine, is a part of the species composition of anti-erosion forests, systems of reclamation and field-protective plantings, landscaping of cities and natural objects having environmental status. The invaders of North American origin, Lepidoptera (Gracellariidae) species pose a main phytosanitary risk for the functioning of R. pseudoacacia in composition of cultured plantings in the steppe zone of Ukraine. The work considered characteristics of the photosynthetic function implementation, specifically, the chlorophyll content and estimated fluorescence coefficients (variable fluorescence and light-adapted steady-state fluorescence value), which can be used to evaluate the functioning of introducents in various landscapes under the condition of such biotic factor as the invasion of Parectopa robiniella (Clemens, 1863). The research was conducted in locations situated in the natural steppe zone of Ukraine within the Dnipropetrovsk Region. A trend towards lower concentrations of chlorophyll in damaged leaves both in shaded and lighted leaves was determined. A reduction in the variable fluorescence intensity was noted, which was greater at the shading of leaves, both in damaged leaves and in leaves without signs of damage from insects (intact leaves). The inhibition intensity of the light stage of photosynthesis was reduced in tree leaves damaged by insects. In the black locust plantations growing in the valley-terrace landscape, steady-state fluorescence values of shaded damaged leaves were significantly lower after light adaptation compared with intact leaves. Mathematical models were developed to calculate the ratio of variable to maximum chlorophyll fluorescence in black locust which comprised plantings in various steppe landscapes with and without damage by P. robiniella.

Keywords

• invasive lepidopterans; trees adaptation in a new range; introduced dendroflora; leaf miner caterpillars; the chlorophyll fluorescence induction curve; biosensor research methods.