Taxonomic importance of seed morphology of Veronica L. subsect. Agrestes Benth. (Plantaginaceae)

Abstract

The study was conducted on five species of Veronica L. subsection Agrestes occurring in Central Europe: Veronica agrestis L., V. polita Fr., V. opaca Fr., V. persica Poir. and V. filiformis Sm. These species are very similar morphologically and are often misidentified. Last thorough studies of morphology and micromorphology of their seeds were conducted in 1960s. Based on 48 herbarium specimens, we examined SEM images of 422 seeds. We found that 22 of the 30 studied morphological traits differentiated five species at statistical level and V. agrestis and V. persica differed with the greatest number of features from other species. Our measurements of seed size were not fully congruent with previous studies, suggesting dependence of these features on external conditions. Seeds were usually cochlidiospermous and ovoid with a reticulate-verrucate seed coat, but these features were, at the same time, quite variable. The results of discriminant function confirmed that some characters of the seed size, shape and coat sculpture could be taxonomically useful in distinguishing species of Veronica subsect. Agrestes. In addition, we believe that similarity of the examined seeds may confirm unity of this group and the need of identifying a subsection.

Taxonomic Significance of Seed Morphology in Veronica L. (Plantaginaceae) Species from Central Europe

“…Only undamaged, fully developed seeds from matured capsules and from well-preserved herbarium specimens were selected for the examinations. In total, 1159 seeds were investigated, including for comparison seeds of the former section Pocilla , used in a previous study ( Table 1 ) [ 35 ]. Dry seeds were attached to table mounts using double sided adhesive carbon discs and then were sputter coated with gold.…”

“…Seed observations were performed using an S-3000N Hitachi Scanning Electron Microscope (SEM). The images were obtained in the Institute of Plant Protection in Poznań, according to the procedure described in Mazur et al [ 35 ]. Seeds of each species were photographed from ventral, dorsal and lateral sides, with magnification from ×35 to ×300 depending on the seed size.…”

“…We examined 462 images of the dorsal side, 453 of the ventral side and 244 of the lateral side. In this number, we included 125 images of the dorsal side, 184 of the ventral side and 113 of the lateral side from a previous study [ 35 ], the measurements of which were made anew. Subsequently, images of the testa sculpture of the 1159 seeds were observed at magnification ×1000, including 422 images prepared in a previous study [ 35 ].…”

“…The examination was focused on the assessment of features of the testa surface; in addition, several other traits indicated as significant by Kulpa [ 29 ] were investigated. For each seed, we determined whether it was cochlidiospermous (that is, ventrally concave) or discoid [ 25 , 28 , 29 , 31 , 32 , 38 ] but with adaptations [ 35 ] to increase objectivity. The discoid ( D ) type of seeds: A thick discoid ( D-tk ) when the value of L / T ½ was less than 3.0 and a thin discoid ( D-tn ) with L / T ½ exceeding or equaling 3.0.…”

“…Further studies were based on SEM images analyses, taking into account the features of the micro-morphological structure of the seed coat sculpture. These works mostly comprised only several species, sampled from a limited area, e.g., from the Mediterranean [ 19 , 30 ], Spain [ 31 ], Iran [ 32 ], Turkey [ 33 , 34 ] and Poland [ 35 ]. For example, Hassan and Khalik [ 36 ] investigated seeds of 29 species mainly from Egypt and Europe.…”