Feb 17, 1999 - and Zigadenus Michx. (including. Amaianthium A. Gray). Downloaded by [Weill Cornell Medical College] at 03:44 07 January 2016 ...
PLANTBIOSYSTEMS,134 (2) 233-240, 2000
Veratrum album and V. nigrum (Melanthiaceae) in Italy: micromorphology and systematics
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M. COLASANTEand RJ. RUDALL
received 17 February 1999; revised version accepted2 November I999
ABSTRACT - Floral anatomy and pollen morphology of the two European species of Veratrum (V. rag,rum and V. album subsp, lobelianum) from Italy are described in the context of the systematics of the genus and tribe Melanthieae (Melanthiaceae sensu stricto). Septal nectaries are absent, as in other Liliales. Most characters in Veratrum are typical of Melanthieae: e.g. semi-inferior ovaries, fused carpellarybundles and operculate pollen. KEY WORDS- floral vasculature, Liliales, Metanthiaceae, Melanthieae, pollen
The north temperate genus Veratrum L. (Melanthiaceae - Liliales- Lilianae) includes about 45 species of relatively large rhizomatous herbs (Figure 1). There are only two species of Veratrum in Europe, including Italy: V. nigrum L. and V. album L.; the latter also occurs in Alaska. V. album presents two subspecies: album and lobelianum (Bernh.) Arcang. (PIGNATTI, 1982). These two species are the only European representatives of the Melanthiaceae sensu stricto, although Zigadenus sibiricus (L) A. Gray occurs in temperate Asia. There is now strong consensus that the Melanthiaceae sensu Iato (e.g. DAHLGRENet al., 1985) are polyphyletic (e.g. CHASE et al., 1995; STEVENSON & LOCONTE, 1995; ZO?~*LEFER,1997; RUDALL et al., 1999). Other genera that were previously assigned to Melanthiaceae, such as Narthecium Huds. and Tofieldia Huds., which both have European representatives, are now considered part of more distantly related families, not closely
related to Veratrum or other Liliales. RUDALL et al. (1999) concluded that Melanthiaceae should exclude disparate non-lilioid dements, such as Tofieldia and Narthecium, but include genera formerly included in Trilliaceae (Daiswa Raf., Paris L. and Trillium L.). The Melanthiaceae have extrorse anthers and ovaries often with three styles. They comprise probably five tribes: Melanthieae (Veratrum and its allies), Chionographideae (Chamaelirium Willd. and Chionographis Maxim.), Heloniadeae (Helonias L., Heloniopsis A. Gray), Xerophylleae (Xerophyllum Michx.) and Trillieae (formerly Trilliaceae). The tribe Melanthieae (four to six genera; formerly Veratreae: KRAUSE, 1930; DAHLGREN et al., 1985; ZOMLEFER, 1997) comprise mostly north American taxa: Schoenocaulon A. Gray, Stenanthium (A. Gray) Kunth., Veratrum (including Melanthium Medik.) and Zigadenus Michx. (including Amaianthium A. Gray).
234 M. COLASANTEAND ~J. RUDALL
This paper presents a detailed description of the micromorphological characters in the two European species of Veratrum (t/7.nigrum and 1,~:album) from Italy, in the context of the systematics of the genus and tribe Melanthieae (Melanthiaceae sensu stricto). There have been relatively few such studies on Veratrum, and those that exist (e.g. STERLING,t982) need to be reassessed in the context of current systematic work.
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MATERIALS AND METHODS Material was collected by one of us (MC) in Italy and fixed in 70% alcohol (for pollen analysis) or in FAA (for flower sections). Both pollen and sections of Veratrum species were obtained from wild populations and/or herbarium sheets. Herbarium specimens are deposited in the Herbarium of the Universita "La Sapienza", Rome. Some flowers for sectioning (those listed HK, below) were obtained from the Royal Botanic Gardens, Kew. Pollen and sections were obtained from the following material: Veratrum album L. subsp, lobelianum (Bemh.) Arcang. (Colasante, 23.7.97, Passo Godi, Abruzzo); V. album (HK 1969-19704); V. nigrum L. (Colasante, 23.7.97, Passo Godi, Abruzzo; 10.7.97 & 25.7.97, Mr. Gennaro, Lazio); V. nigrum (HK 195872401). Pollen of Schoenocaulon caricifolium Greenm. (HK 1990-2318) and Zigadenus venosus Watson was included for comparison (Figure 5).
Pollen samples were obtained by fixing anthers or free pollen in 70% alcohol directly in the field; they were prepared for SEM (Cambridge 2000) examination using a critical-point drier after a dehydration series up to 100% ethanol and coating them with gold. Samples for sectioning consisted of complete flowers or ovaries. They were embedded in Paraplast using standard methods of wax embedding, and serially sectioned using a rotary microtome. Sections were stained in Saffanin and Alcian blue, dehydrated through an alcohol series to 100% ethanol then Histoclear, mounted in Eupara], and examined using a Leitz Dialux 20 photomicroscope.
RESUEFS Mthough the two species are normally easy to distinguish, since V album has greenish-yellow flowers (Figure la) and V. ,igrum dark red/purple ones with reflexed tepals (Figure Ic), we often observed specimens of V album and V nigrum growing very close together in the same area so that they appeared as a single population. Furthermore, although both species have similar paniculate inflorescences, those of V album have longer branches (Figure lb) with longer subtending bracts than those of V nigrum. V album has broad, elliptica] leaves which are densely hairy on the abaxial surface, whereas in V nigrum the leaves are almost glabrous and ranging from broad to narrow and Ianceolate. Both species
FIGUI',E1 - (a) V albumsubsp.[obelianum,flowerswithpatenttepalsshowingV-shapedspotand streaks;(b) V albumsubsp,lobeIianum,plants in their wildsite; (c) V nigrum,flowerswkh reflexedtepals (seetext).
Micromorphology and s3,stematicso/Veratrum 235
Ovary and ovules The gynoecium in V. album and 1
