The taxonomic implication of leaf micromorphological characteristics in the genus Aruncus (Rosaceae)

A comparative study of leaf epidermal microstructures in genus Aruncus (two species, five varieties) was carried out using scanning electron microscopy in order to evaluate their significance in terms of taxonomy. All of the leaves of the taxa studied here were amphistomatic with undulate anticlinal walls, and smooth and flat periclinal walls on both surfaces. The size range of the stomata complex is 8.95-21.97 × 7.50-16.99 μm: The largest one was found in Aruncus dioicus var. astilboides (average 18.01 × 13.47 μm) and the smallest was measured and determined to be A. gombalanus (average 11.11 × 8.94 μm). An anomocytic stomata complex was found in all of the studied taxa. The stomatal frequency on average was 27.54/0.05 mm2; it is highest in A. gombalanus (60.4/0.05 mm2) and lowest in A. dioicus var. acuminatus (11.6/0.05 mm2). Two types (short stalked capitate glandular trichome and non-glandular trichome) of trichomes are found in the leaves. The non-glandular trichome was divided into three types based on the presence and degree of development of subsidiary cells. Anomocytic stomata of the hypostomatic type and the distribution pattern of capitate glandular trichomes were the major characters in this genus. The stomata size and frequency, the epidermal cell structure, the trichome type and the distribution pattern may have diagnostic importance among the taxa in the genus. Our leaf micromorphological results provide useful information for the taxonomic revision of the genus Aruncus.