Effects of atmospheric dust deposition on leaf chlorophyll fluorescence parameters of cow-tail shrubs (Smirnovia iranica) in the desert regions of Kashan, Iran

Smirnovia iranica, a native valuable woody species from Fabaceae, is an adaptable plant from the central sandy areas of Iran. Changes in chlorophyll fluorescence and photosynthetic pigment characteristics were analysed in the course of dust accumulation during April (Ap); April and May (AM); and April, May and June (AMJ) periods, respectively. The results obtained from the analysis of variance indicated that there was a significant difference among different dust-loading periods of S. iranica in terms of the characteristics mentioned. Extending dust accumulation resulted in a significant reduction in the Fv /Fm ratio in AM and AMJ. A significant effect of dust deposition on thermal dissipation of the light energy (D) value was observed in AM and reached the highest value in AMJ. In all evaluated plants, during the course of dust accumulation, there was a decrease in the photochemical efficiency of photosystem II (?PSII), and from AM. A similar influence of the extending dust accumulation periods on ?PSII was observed for the electron transport rate (ETR). Our results proved that dust deposition decreased overall plant performance through its severe effect on pigment content and resulted in a significant inhibition of PSII efficiency throughout this study period.