Effects of particulate matter contamination on peach leaf physiological functions

During the summer, precipitation events occur rarely in the Mediterranean region. This results in cement kiln dust deposition on crops grown around cement factories or soil dust deposition on crops grown next to unpaved farm roads. The purpose of this study was to investigate the effects of particulate matter contamination from cement kiln and soil dust on peach leaf physiological characteristics and functions. Cement kiln dust and soil dust were applied periodically during the summer 2009 in ‘Royal Glory’ peach trees (fruit harvested early July) located away from contamination sources. Dust accumulation on treated peach leaves and various leaf physiological parameters were measured periodically over the summer period until late September. Specific leaf mass increased and chlorophyll content decreased after harvest and remained unchanged over the summer due to summer heat stress or, most probably, due to low ‘sink’ demand. Leaf gas exchange functions significantly decreased in June due probably to soil drying and transition of the functioning root system from the whole soil profile to the drip irrigated areas only. Contaminated leaves progressively accumulated soil and cement dust over the summer. This contamination resulted in increased specific leaf mass and decreased leaf chlorophyll content compared to leaves from control plants (uncontaminated). Peach leaves dusted with soil and cement had lower stomatal conductance and transpiration and photosynthetic rates than control leaves throughout the summer period. In May, at the beginning of particulate matter application, and in late September, when rains had removed substantial part of the deposited dust, leaf functions were similar in all treatments. The presence of cement or soil dust contamination did not cause any macroscopic toxicity to peach leaves. But the reduction in leaf productivity may have negative consequences on yield and, possibly, fruit quality, especially for the mid-season and late ripening peach cultivars.