SEED MORPHOLOGY AND TESTA SCULPTURES OF SOME Allium L . SPECIES ( Alliaceae )

The paper presents the results of the study on seed morphology of eight following Allium species: A. pyrenaicum Costa & Vayr., A. rotundum L., A. sphaerocephalon L., A. vineale L., A. moly L., A. karataviense Regel, A. fistulosum L. and A. nutans L. The study confirmed the substantial diversity in testa characters, especially curvature and relief of anticlinal walls as well as microsculpture of outer periclinal walls. The occurrence of raised anticlinal walls – an unusually rare feature in Allium seeds, previously observed only in a few species, was found in A. karataviense. It was also found that the testa type in A. pyrenaicum did not match the typical character combination, described before for subg. Allium sect. Allium.


INTRODUCTION
Allium L. is a large, very diverse and taxonomically difficult genus of the monocots.The genus comprises about 800 species belonging to 15 subgenera and 56 sections (F r i e s e n et al. 2006; N e s h a t i and F r i t s c h , 2009).The most important subgenera are: Allium, Amerallium, Cepa, Melanocrommyum, and Rhizirideum.Most species occur naturally in the northern hemisphere with the main centre of diversity in Southwest and Central Asia.Allium includes many cultivated species -mostly ornamental plants but also economically important crop species and some with medicinal properties.
A high level of morphological diversity ascertained in the genus Allium concerns also seed testa characters whose details are well visible under the scanning electron microscope (SEM).A large number of different testa types have been described so far (e.g.K r u s e , 1984,1986,1988,1994 et al. 2006).The other seed characters, such as colour, size and shape, were considered to be taxonomically rather unimportant characters in the genus Allium (N e s h a t i and F r i t s c h , 2009).
The aim of the presented work was to describe testa sculptures of some selected Allium species, not investigated so far: A. pyrenaicum Costa & Vayr., A. rotundum L., A. sphaerocephalon L., A. vineale L., A. moly L., A. karataviense Regel, A. fistulosum L., and A. nutans L. Micromorphological characters of seeds may be useful as additional taxonomic features in identification and distinguishing taxa within the genus Allium.

MATERIALS AND METHODS
Seeds of eight Allium species representing the most important five subgenera were investigated.Seeds were collected in natural localities, in a collection of Poznań University of Life Sciences, and in the Botanical Garden of Adam Mickiewicz University in Poznań (Table 1).All examinations were carried out on fully developed dry seeds.The seeds were not specially prepared, but only cleaned.Size (length and width), shape, outline, and seed colour were determined from 30 seeds of each species using a stereoscope microscope, PZO type 131.Five seeds of each species were mounted on aluminium stubs with "Leit-Tabs" and coated with gold in an Agar sputter coater.Electron micrographs were obtained with a Zeiss EVO 40 scanning electron microscope at an accelerating voltage of 12 kV.The terminology describing the seed surface followed mainly B a r t h l o t t (1981,1984).

RESULTS
The main macro-and micro-morphological characters of the investigated seeds are summarized in Table 2, and the selected SEM microphotographs of the seed showing a general view and testa details are presented in Figs 1-8.

General morphological characters
The seeds of all investigated species were black; matte in A. karataviense, and slightly shiny in the remaining species.The shape of seeds was generally angular; most often with four walls in A. fistulosum, three walls in A. sphaerocephalon, and two walls in the remaining species.The seed outline was very variable -elliptic, roundish, obovate, or wide ovate.The seeds of A. fistulosum were outstanding in this respect, because they were wider than longer.The average seed size ranged from 2.5 mm (A.vineale) to 3.1 mm (A.karataviense) in length and 1.4 mm (A.vineale) to 2.9 mm (A.karataviense) in width.Thus, A. vineale had the smallest and A. karataviense the largest seeds.

Shape and sculpturing of testa cells
The shape of testa cells was very variablefrom elliptic and circular to polygonal and irregular.The anticlinal walls were usually depressed, except the raised ones in A. karataviense.They were more or less straight, strip-like in A. pyrenaicum (Fig. 1a), A. fistulosum (Fig. 7a) and A. nutans (Fig. 8a), and S-like, U-like or Omega-like undulated in the remaining species.Sculpturing patterns of the periclinal walls were not very variable among the species investigated.Most common were convex, granulose walls bearing several verrucae.A. pyrenaicum (Fig. 1a) had flat, distinctly granulose walls with a central verruca.A. moly (Fig. 5a) showed flat, not granulated walls, most often with one central verruca.A. fistulosum (Fig. 7a) had densely granulose walls with no verrucae, and A. nutans (Fig. 8a) were distinctive of very densely granulose walls and hidden, indistinct central verruca.

Table 1 .
Origin of the material (taxonomic groups after F r i e s e n etal.2006)

Table 2 .
Seed size and outline as well as characters of epidermal cells