Plant Syst. Evol. 248: 219–241 (2004) DOI 10.1007/s00606-004-0182-7 Gunnera herteri – developmental morphology of a dwarf from Uruguay and S Brazil (Gunneraceae) R. Rutishauser1, L. Wanntorp2, and E. Pfeifer1 1Institute of Systematic Botany, University of Zurich, Zurich, Switzerland 2Department of Botany, University of Stockholm, Stockholm, Sweden Received January 26, 2004; accepted March 31, 2004 Published online: August 30, 2004 Ó Springer-Verlag 2004 Abstract. New morphological and developmental Key words: Gunnera, Ostenigunnera, Panke, Nostoc, observations are presented of Gunnera herteri axillary glands, basal eudicots, congenital fusion, (subgenus Ostenigunnera) which is, according to development, sympodial growth, unisexual flowers. molecular studies, sister to the other species of Gunnera. It is an annual dwarf (up to 4 cm long) whereas the other Gunnera spp. are perennial and slightly to extremely larger. External stem glands Developmental morphology of Gunnera herteri. are combined with channels into the stem cortex Gunnera is a genus of flowering plants that serving as entrance path for symbiotic Nostoc cells. includes 30–40 species with a mainly southern Young stem zones show globular regions of cyto- distribution. Schindler (1905) divided Gunnera plasm-rich cortex cells, prepared for invasion by into five subgenera based on the size of the Nostoc. The leaf axils contain 2–5 inconspicuous plants, their means of propagation and their colleters (glandular scales) which can be taken as geographical distribution. Mattfeld (1933) cre- homologous to the more prominent scales of ated the new subgenus Ostenigunnera to G. manicata (subg. Panke) and G. macrophylla include a new species of Gunnera, discovered (subg. Pseudogunnera). Foliage leaves of G. herteri in a small oasis among the sand dunes of the have tooth-like sheath lobes which may be homol- Bay of Rocha (Uruguay). This species was ogous to stipules. Adult plants have extra-axillary inflorescences arising from leaf nodes. The main named G. herteri to honour W. Herter, who stem is interpreted as a chain of sympodial units, together with C. Osten found and collected the each one consisting of a leaf and an extra-axillary plant (see Osten 1932). Morphological and inflorescence. This ‘‘sympodium hypothesis’’ may anatomical studies on the shoot and the be also valid for other species of Gunnera. Each vascular systems, respectively, together with globular inflorescence of G. herteri contains several the presence of symbiotic cyanobacteria of the female flowers and 2–7 stamens at the top, perhaps genus Nostoc, showed that the tiny plant really equalling a single male flower. There are neither belonged to the genus Gunnera (Mattfeld bracts nor bracteoles. The ovary is inferior, 1933). bicarpellary and unilocular. Its single hanging ovule develops into a dry and endosperm-rich Gunnera herteri is a rare plant with a very seed. restricted distribution. Except for the district 220 R. Rutishauser et al.: Gunnera herteri – developmental morphology of a dwarf of Rocha in Uruguay, the plant occurs in The morphology of mature plants of similar environments in the adjacent districts G. herteri was studied by Mattfeld (1933). of Rio Grande and Santa Catarina (Brazil) Various questions about reproductive struc- where it is called ‘‘Urtiguinha das Dunas’’. tures and the developmental morphology of These very few localities for G. herteri are the plant could not be elucidated due to the endangered by the constructions of tourist scarce material available. Recently, the vege- resorts on the beaches and by pine planta- tative anatomy of G. herteri was examined for tions planted to stop the movement of the the first time by Wilkinson (2000) in a study sand. Due to its narrow distribution, Gunnera mainly based on light microscopy of herbar- herteri has been collected very sparsely during ium material. Except for these studies, no the past hundred-and-ten years. The first comprehensive morphological study based on collection of G. herteri was made by the SEM has so far been presented and there is at Swedish botanists Lindman and Malme, twice present no study on the flower morphology of in Santa Catarina, as early as in 1892 and in G. herteri. 1901, respectively, but their herbarium speci- The principal aim of this study is to present mens remained unnamed for more than 30 the developmental morphology of G. herteri in years at the Swedish Museum of Natural detail by using SEM and microtome/light History. Gunnera herteri has to the best of microscope techniques on fresh material. A our knowledge only been collected in Brazil brief comparison between some morphological twice since that time. In Uruguay the plant and anatomical characters of G. herteri and has also been collected twice since its first some other species of Gunnera is here also discovery; once by E. Paz in 1989 and again reported. by L. Wanntorp (the second author of this paper) in 1997. Thanks to the extensive research of the past few years on the systematics of Gunnera, new Material and methods data on G. herteri have come to light. The cultivation of G. herteri proved that the plant • Gunnera herteri Osten (subgenus Ostenigunnera): is not a perennial as stated by older literature fruits and alcohol-fixed material collected 1997 (Osten 1932, Mattfeld 1933). In fact, it is the in Uruguay by L. & H-E. Wanntorp 555 (S); single annual species within the genus. In other fresh material was cultivated in the phylogenetic studies on the genus, based on Botanical Garden of Stockholm. both molecular and morphological data (Wan- • Gunnera manicata Linden (subgenus Panke): torp and Wanntorp 2003; Wanntorp et al. cultivated in the Botanical Garden of Zurich 2001, 2002, 2003), G. herteri was found as University (since 1949, source unknown). sister to the remaining species of the genus. The plant specimens used were fixed and pre- This phylogenetic position is useful for clari- served in 70% ethanol. Preserved material stored fying the historical biogeography of this spe- in 70% ethanol was used for light and scanning cies. South America is often considered as a electron microscopy (SEM). For microtome composite area in biogeographic studies sections, specimens were embedded in Kulzer’s (Wanntorp and Wanntorp 2003). The area Technovit (2-hydroethyl methacrylate), as described in Igersheim and Cichocki (1996), and where G. herteri occurs today was, together sectioned with a HM 355 rotary microtome and with West Africa, part of an extensive area conventional microtome knife type C and D. The united along the Guinea fracture zone until mostly 7 lm thick sections were stained with about 105 mya (Albian, Cretaceous). In light ruthenium red and toluidine blue. The permanent of this, Gunnera herteri could be interpreted as slides of the microtome sections are deposited at a relict taxon from that area (Wanntorp and the Institute of Systematic Botany of the Univer- Wanntorp 2003). sity of Zurich (Z). R. Rutishauser et al.: Gunnera herteri – developmental morphology of a dwarf 221 Results globular regions of cytoplasma-rich cortex cells which are prepared for being invaded by Habit. Gunnera herteri is a tiny annual, Nostoc (Fig. 15). After infection Nostoc pro- forming dense mats on seepage ground liferates within the cortex cells (Fig. 16). There between the coastal dunes of Uruguay and are intercellular cavities in the surrounding southern Brazil. It has branched stems 2–4 cm stem cortex. long (diameter 0.5–1 mm) with spirally Morphology and development of foliage arranged foliage leaves (Figs. 8, 35, 64). There leaves. Fully grown foliage leaves consist of a are no stolons. Vegetative lateral shoots arise stalk 6–7 mm long and a cordate to kidney- from the leaf axils and repeat the upright shaped blade which is crenate or slightly lobed growth of the main stem. In addition, there are (up to 4 mm long, 7 mm broad, Fig. 64). Each 1(–2) cm long stalked tiny inflorescences (one blade lobe (or crenation) is topped by a per leaf). They are inserted extra-axillary, on marginal hydathode (Figs. 24, 25). The palmate the right or left side of the insertion area of a blade venation divides up into fine reticulate foliage leaf (Fig. 40). Most roots are secondary vascular bundles (Fig. 28). Anomocytic sto- (‘‘adventitious’’) arising endogenously from mates are found on both the upper and lower the stem whereas the primary root (radicle) blade surface (Figs. 26, 27). The blade meso- seems to wither soon (Figs. 3, 4). phyll consists of a layer of moderately elon- Anatomy of stems and roots. Transverse gated palisade cells and 1–3 layers of spongy stem sections show a central stele, consisting of cells (Fig. 29). The young blade in the bud stage a hollow vascular cylinder with lacunae for the shows involute vernation, i.e. the lateral blade entering leaf traces (Figs. 1, 13). Occasionally portions are rolled towards the upper (ventral) there is additional vascular tissue in the side (Figs. 9, 23). Three petiole bundles enter parenchymatous pith (Figs. 2, 16). The sur- the blade (Figs. 35, 38). They are fused into one rounding parenchymatous stem cortex con- leaf trace near the petiole insertion (Fig. 39). tains cavities which are filled with endogenous Each petiole base is usually broadened into a roots and Nostoc colonies. Many endogenous sheath with two attached lobes resembling roots protrude from the surface of the stem lateral stipules (Figs. 12, 17, 20). Sheath lobes base, from nodes as well as internodes (Figs. 3, of young leaves next to the terminal bud border 4) while there are no adventitious roots higher the early present Nostoc glands (Figs. 8–11). up. Each root is provided with a prominent Primary leaves (including seedling leaves, cot- cap (Figs. 5, 6). The root cortex shows narrow yledons) are entire, lanceolate and lacking peripheral cells and wider cells towards the sheath lobes (Figs.