Parameters for Induction Curves of Prompt and Delayed Fluorescence and Redox State of PSI–P700 for Birch and Linden Leaves in Various Urban Environments

Abstract

The photosynthetic characteristics of linden leaves (Tilia cordata L.) and birches (Betula verrukosa L.) growing near the city highways of Moscow (MKAD, Moscow Ring Road) by simultaneously recording the induction curves of chlorophyll fluorescence and the redox state of the PSI pigment–P700. In trees near highways, deterioration of electron transport at the level of plastoquinones (δRo) and decrease of P700+ reduction was revealed, despite the rather high rates of photosynthetic efficiency (FV/FM). In birch leaves growing along the Moscow Ring Road, a decrease in the outflow of electrons from PSI and a decrease in the intensity of delayed fluorescence at 30 ms and 1 s, associated with a decrease in the electrical and chemical components of the electrochemical proton gradient on photosynthetic membranes, were revealed. In plants near highways, an increase in the degree of photoinhibition and a slowdown in the reactions of restoring photosynthetic activity in the dark after the cessation of photooxidative stress were noted, which confirms the probable effect of unfavorable urban conditions on the biosynthesis of proteins in PSII reaction centers. The following fluorescence parameters are proposed as indicators of the state of trees in an urban environment: total performance index (PItotal) and the quantum yield of reduction of electron acceptors on the acceptor side of PSI (φRo).