Pollen micromorphology of Arabis procurrens and A. hirsuta (Brassicaceae) grown in Jerma River Canyon in Serbia

Abstract

Two Arabis species (family Brassicaceae) from the Jerma Special Nature Reserve, located within the Dinaric Mountain Range, in the far southeast of Serbia, have been palynomorphologically analyzed to contribute to taxonomic and mellisopalinological research. Natural habitat for both Arabis species, namely Arabis hirsuta (L.) Scop. (hairy rock-cress) and Arabis procurrens Waldst. & Kit. (running eared-rockcress) is rocky mountain/cliff sides, limestone slopes, rocks and walls, or dry sites. Moreover, the latter is a subendemic species to the Balkans. The pollen morphology was examined by scanning electron microscopy (SEM). Pollen grains were photographed in polar and equatorial view and the following features were examined: length of polar (P) and equatorial axis (E), shape, ornamentation, apertures, polarity, symmetry. The pollen grains of both Arabis species are isopolar, radially symmetric and medium-sized. According to T-test (p<0.05), P of A. hirsuta are a bit longer (P:32.8 ± 2.93 μm) relative to A. procurrens (P:30.1 ± 1.8 μm), while there is no statistically significant difference in E (17,7± 1.5 μm : 18.2 ± 1.3 μm), which slightly affects the shape. The P/E ratio in A. hirsuta and A. procurrens amounts 1.9 ± 0.2 and 1.7 ± 0.1, respectively, indicating prolate shapes. In equatorial view both pollen grains are elliptic and in polar view are three-lobate with interangular furrows. The grains are tricolpate with ectocolpi arranged regularly meridionally, of mean length 27.3 ± 1.4 μm (A. hirsuta) and 24.5 ± 1.2 μm (A. procurrens). Mesocolpium is slightly wider in A. procurrens (11.7 ± 0.6 μm) than in A. hirsuta (10.7 ± 0.4 μm). The exine ornamentation is reticulate with polygonal lumina of similar size among the species studied, while muri in A. hirsuta are narrower.