Evaluation of the stomatal characteristics of Quercus castaneifolia C.A.M. and Carpinus betulus L. under the dust pollution of Mazandaran cement factory

Dust particles can cause disturbance in photosynthetic activities by passing through the openings and thus reduce plant growth. The present study examines the effect of cement dust pollution on the characteristics of leaf stomata in two important tree species of Hyrcanian forests in northern Iran. For this purpose, the leaves of oak (Quercus castaneifolia C.A.M.) and common hornbeam (Carpinus betulus L.) were sampled in two polluted and control sites around the Mazandaran cement factory. The characteristics of density, width, length, perimeter, and area of stomata and guard cells were measured. The results showed that the average stomatal density for oak and common hornbeam in the polluted site (36.1 and 6.6 stomata per mm2, respectively) is significantly higher than the control site (24.3 and 2.5 stomata per mm2, respectively). Based on the results, the characteristics of stomatal width and length as well as guard cell width and length in oak did not show any significant difference between the two polluted and control sites. In common hornbeam species, the average width and length of the stomata in the polluted site (40.5 and 75.2 µm, respectively) were significantly lower than the control site (46.8 and 90.4 µm, respectively). Also, in the oak species, the ratio of stomatal length to width in the polluted site (3.5) was significantly higher than in the control area (3.1), but no significant difference was observed in the common hornbeam species. Finally, the oak species showed better resistance than the common hornbeam species by increasing the stomata density without a significant change in the characteristics of the length and width of the stomata and the guard cell.