Importance of micromorphological characteristics of foliar and pollen grains for delimitation of Oak species in Iran

Several species of oaks (Quercus spp.) grow abundantly in the Hyrcanian, Arasbaran and Zagros forests of Iran. Taxonomy of oaks is difficult because of it's immense size and wide distribution, heterophylly, hybridization and changes in morphological features. Micromorphological characteristics of foliar and pollen features provide a valuable set of analytical characters for species delimitation in Quercus, so it's the goal of recent studies in taxonomy of genus Quercus. In this research, for the first time in Iran, some of micromorphological characteristics of foliar (type of trichomes, the number and length of trichome rays, type of epicuticular waxes, type and shape of stomata), and pollen (shape and exine ornamentations) were studied in six Quercus species (Q. castaneifilia C.A.Mey. subsp. castaneifolia, Q. macrantheraFisch. and C.A.Mey. ex Hohen., Q. petraea L. ex Liebl.subsp. iberica (Steven) Krassiln., Q. libani Oliv.,Q. infectoria Oliv.subsp. boissieri (Reut.) O.Schwarz and Q. brantii Lindl. subsp. brantii var. brantii Zohary). The mentioned species have been accepted by different botanists and foresters. The samples were prepared from individuals in nature and the herbarium specimens and photographed by SEM and LM. Overall, five types of trichomes, two types of epicuticular waxes, four shapes of pollens, four types of structural patterns of tectum surface, four types of sculptural patterns and three types of suprasculptural patterns of pollens were recognized in the studied taxa. The most important and valuable characteristics in the studied taxa were type of trichome, the number and length of trichome rays and shape of pollen in    Q. macranthera and Q. petraea subsp. iberica; shape and exine ornamentations of pollen in Q. infectoria subsp. boissieri and type of trichome, shape and exine ornamentations of pollen in Q. castaneifolia subsp. castaneifolia, Q. libani and Q. brantii subsp. brantii var. brantii. Based on our results, the studied micromorphological characteristics have high taxonomic value in the differentiation of Quercus species, and when employed in combination with other morphological features permit correct species identification.