Abolfazl Ranjbar - Associate Professor, Faculty of natural resources. University of Kashan, Kashan, Iran.
Ehsan Zandi Esfahan - Assistant Professor, Rangeland Research Division, Research Institute of Forests and Rangelands, Agricultural Research, Education and Extension Organization, Tehran, Iran.

Smirnovia iranica, a native valuable woody species from Fabaceae, is an adaptable plantfrom the central sandy areas of Iran. Changes in chlorophyll fluorescence andphotosynthetic pigment characteristics were analysed in the course of dust accumulationduring 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 asignificant difference among different dust-loading periods of S. iranica in terms of thecharacteristics mentioned. Extending dust accumulation resulted in a significant reductionin the Fv /Fm ratio in AM and AMJ. A significant effect of dust deposition on thermaldissipation of the light energy (D) value was observed in AM and reached the highest valuein AMJ. In all evaluated plants, during the course of dust accumulation, there was adecrease in the photochemical efficiency of photosystem II (ΦPSII), and from AM. Asimilar influence of the extending dust accumulation periods on ΦPSII was observed for theelectron transport rate (ETR). Our results proved that dust deposition decreased overallplant performance through its severe effect on pigment content and resulted in a significantinhibition of PSII efficiency throughout this study period.

Dust, Electron transport rate, Photosynthetic apparatus, Thermal dissipation, Pigment