Cell Pattern and Ultrasculpture of Bulb Tunics of Selected Allium Species (Amaryllidaceae) and their Diagnostic Value

Cell pattern and ultrasculpture were examined by light and scanning electron microscopy in bulb tunics of 46 Allium species to determine the diagnostic value of micromorphological characters. The study examined the diversity of these characters, evaluated their usefulness at different taxonomic levels (species, section, subgenus), and considered the results in relation to the recent intrageneric classification of the genus. Detailed characteristics are provided for the investigated species, and taxa showing the presence of calcium oxalate crystals in bulb tunic cells are indicated. The results suggest that several bulb tunic characters are of taxonomic significance in Allium as their variation between specimens of the same species was negligible; they can be useful elements of species descriptions and determination keys. Allium subgenus Allium shows considerable variation of bulb tunic ultrasculpture and hexagonal or elongated cell patterns. Differences in ultrasculpture are sufficient to distinguish species within the Amerallium subgenus. Three subgenera ( Anguinum , Butomissa , Reticulatobulbosa ) are characterized by fibrous tunics with reticulate ultrasculpture. Rectangular to elliptic cells with thick walls, giving the bulb tunic an almost perforated structure, are characteristic for Allium subgenus Cepa . No specific pattern was found for Allium subgenus Melanocrommyum and Polyprason . The only representative of subgenus Microscordum ( Allium monanthum ) showed distinct herringbone ultrasculpture. The bulbs of Allium subgenus Rhizirideum representatives can be distinguished by their linear ultrasculpture following the long axis of the elongated cells. Allium bulb tunic ultrasculpture and cell pattern show some degree of variability. These characters are of potential use in taxonomic delimitation, species determination and further study of the relation- ships between Amerallium