objective  Photosynthesis in relation to dust retention of leaves on 8 species of arbor trees in the city of Qingdao was studied for urban landscape planning.

  methods  The 8 species planted on the greenbelt at Chengyang District in the city were tested for their dust retention capabilities by means of water elution. Before and after a dust collecting period, surface of the tree leaves was examined under a JEOL7500F electron microscope, and the photosynthetic rate determined by a photosynthesis instrument.

  results  The average dust retained per unit leaf area of the trees after an autumn rain ranked in the order of Prunus cerasifera > Platanus orientalis > Ligustrum lucidum > Fraxinus pennsylvanica > Populus tomentosa > Sophora japonica > Koelreuteria paniculata > Salix matsudana. In general, the net photosynthetic rate, intercellular CO₂ concentration, stomatal conductance and transpiration rate of the leaves all declined after a dust covering. In 60 days of continuous dust-fall on the leaves, these indicators steadily decreased and recovered only to some extent after dust removal. The greatest losses on photosynthesis among the 8 species occurred upon L. lucidum, followed by T. tapeanum and R. japonica. The losses by percentage were relatively low for K. paniculata and P. cerasifera. A correlation analysis showed a best fitted model between the rate of photosynthetic losses and the dust retention per unit leaf area for the 8 species to be a polynomial equation.

  conclusion  Among the species, P. cerasifera exhibited the greatest dust retention capability, while S. matsudana the least. The leaves of S. matsudana, L. lucidum and R. japonica were poor in resisting atmospheric dust, while those of L. lucidum and P. cerasifera seemed strong. A significant correlation between the rate of photosynthesis loss and dust retention of tree leaves was found for the 8 species. The more dust covered the leaves, the greater degree of tree photosynthesis was in jeopardy. There also were significant correlations among the various photosynthetic indicators of the tree leaves.