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

Abstract

In this study, 1159 seeds of 29 Central European species of the genus Veronica were analyzed based on scanning electron microscopy images. The species belonged to nine subgenera: Beccabunga, Chamaedrys, Cochlidiosperma, Pellidosperma, Pentasepalae, Pocilla, Pseudolysimachium, Stenocarpon and Veronica, following the newest phylogenetic classification of the genus. Nine measured characteristics of seeds and nine ratios were analyzed statistically using ANOVA followed by post hoc testing, cluster analysis and discriminant analysis. In most cases, the results were not congruent with the contemporary classification of the genus. Examinations of qualitative seed features by scanning electron microscopy included the cochlidiospermous or discoid seed type, the seed shape, the general sculpture of the seed coat surface, the sculpture of anticlinal and periclinal walls and some species-specific traits such as the presence of the epidermal appendix. All these features, apart from seed shape, were useful to distinguish all subgenera and some species within subgenera: Beccabunga, Chamaedrys, Pellidosperma, Pocilla (only V. filiformis) and Veronica. The identification key based on the seed micromorphological features was prepared.

Keywords: micromorphology; numerical analysis; scanning electron microscopy; seed; seed coat.

Figure 1

Cochlidiospermous (ventrally concave) seeds of Veronica species. (A) V. hederifolia—deep cochlidiospermous, large seed; (B) V. polita—shallow cochlidiospermous, small seed, with deeply wrinkled surface; (C) V. persica—small, obovoid seed with deeply wrinkled surface; (D) V. praecox—deep cochlidiospermous seed with smooth surface; (E) V. triphyllos—shallow cochlidiospermous seed with smooth surface; (F) V. triphyllos—broadly obovoid shape in outline with a trace of micropyle in the form of a shallow pore (arrow); (G) V. praecox—broadly obovoid seed with a trace of micropyle in the form of a deep pore (arrow); (H) V. filiformis—broadly obovoid seed with the large chalazal plate raised on the plateau, with large polygonal structures on the chalaza (without papillae), the sculpture of the remaining seed surface is reticulate-verrucate, polygons small; (I) V. sublobata—reticulate-corrugate sculpture with convex, corrugate anticlinal walls and flat, rugose periclinal walls.

Figure 2

Discoid, small seeds of Veronica species; (A) V. longifolia—discoid-thin seed; (B) V. anagalis-aquatica—discoid-thick seed; (C) V. peregrina—discoid-thick seed with a keel; (D) V. longifolia—elliptical seed with the reticulate-striate sculpture; (E) V. longifolia—reticulate-striate sculpture with convex, striate anticlinal walls and concave, striate periclinal walls; (F) V. anagalis-aquatica—reticulate sculpture with convex, rugose anticlinal walls with lumps and slightly colliculate, granulate periclinal walls; (G) V. serpyllifolia—reticulate-verrucate sculpture with convex and rugose anticlinal walls and rugose periclinal walls, with large papillae; (H) V. beccabunga—reticulate sculpture with convex anticlinal walls and slightly colliculate, granulate periclinal walls; (I) V. catenata—reticulate sculpture with convex, rugose anticlinal walls and concave, corrugate periclinal walls.

Figure 3

Discoid, large seeds of Veronica species; (A) V. austriaca—broadly elliptical seed with thick but shallow wrinkles on the surface; (B) V. teucrium—broadly obovoid seed with large chalazal plate and epidermal appendix in the upper part of the chalazal plate (arrow); (C) V. aphylla—broadly elliptical shape in outline with small chalazal plate; (D) V. chamaedrys—broadly elliptical seed with large chalazal plate and epidermal appendix in the upper part of the seed, outside chalazal plate (arrow); (E) V. austriaca—suborbicular shape seed with epidermal appendix in the upper part of the chalazal plate (arrow); (F) V. verna—broadly elliptical seed with large chalazal plate and no epidermal appendix; (G) V. scutellata—broadly elliptical shape in outline with chalazal plate at approximately half of the length of the seed; (H) V. fruticans—broadly elliptical seed with chalazal plate in the upper part of the seed, verrucate seed coat; (I) V. chamaedrys—reticulate-verrucate-colliculate sculpture with convex, corrugate periclinal walls and flat, rugose anticlinal walls.

Figure 4

Discoid, large seeds of Veronica species; (A) V. arvensis—reticulate-verrucate sculpture with convex, rugose anticlinal walls and with rugose, corrugate periclinal walls, with papillae not clearly visible; (B) V. dillenii—reticulate-verrucate sculpture with convex, rugose anticlinal walls and with flat, rugose, corrugate periclinal walls and with papillae clearly visible; (C) V. verna—reticulate-verrucate sculpture with convex, rugose anticlinal walls and with flat, rugose and granulate periclinal walls, with papillae clearly visible; (D) V. montana—reticulate sculpture with supracellular rings, with convex anticlinal walls and colliculate periclinal walls; (E) V. montana—broadly elliptical shape in outline, supracellular rings, seed surface smooth; (F) V. aphylla—broadly elliptical shape in outline, seed surface wrinkled; (G) V. officinalis—reticulate sculpture with convex, smooth anticlinal walls and colliculate, granulate periclinal walls, polygonal structures small; (H) V. scutellata—reticulate sculpture with convex, smooth anticlinal walls and colliculate, smooth periclinal walls, polygons large; (I) V. urticifolia—broadly elliptical shape in outline with large polygons around the chalaza.

Figure 5

(A) UPGMA dendrogram constructed on the shortest Euclidean distances for nine subgenera of the genus Veronica, based on quantitative traits; (B) simplified tree showing the relationships between the analyzed subgenera of Veronica, based on the fragment of combined cpDNA and ITS phylogeny by Albach and Meudt [10]; only the binding order is shown; (C) UPGMA dendrogram constructed on the shortest Euclidean distances for 29 species of the genus Veronica, based on quantitative traits. Subgenera abbreviations as in Table 1.