AMORPHOPHALLUS TUBERCULATUS
PROTOLOGUE: Amorphophallus tuberculatus Hett. & V.D.Nguyen, published in Aroideana 29: 77 (2006).
Amorphophallus tuberculatus Hett. & V.D. Nguyen sp. nov. Hic species unicus tubere globoso quo inflorescentia iuxta folium maturum moribundum crescet, statim folium mortuum floret. In pluribus characteribus ceteris Amorphophallo yunnanensis gregem proximus ut videtur spatham spadicisque proprietates, odorem iucundum partirentes. Pro Amorphophallo tuberculato unicus tuber verrucis magnis baciliformibus carneis nullo modo radicum cicatricibus associatis. Type: from a plant cultivated in the Botanical Gardens of Wageningen University (orig. coll.: NORTH VIETNAM, Quang Binh Province, Bo Trach District, Phong Nha-Ke Bang Natl. Park, Son Trach Community, “damaged secondary evergreen forest on a slope of a limestone mountain, alt. ca. 300 m”, V.D. Nguyen et al. 214), 28 February 2005, Hetterscheid H.AM.1319-T (holotype, WAG, spirit collection).
DISTRIBUTION: Vietnam: Vietnam.
DISTRIBUTION NOTE: Vietnam: Quang Binh Province, in the Bo Trach district within Phong Nha-Ke Bang National Park - the only locality known.².
SPECIES DESCRIPTION:
Tuber depressed globose, about 10 cm across and 8 cm high, densely covered with thick, short, elongate protrusions that are not associated with root scars. Petiole 50 cm long and 2.5 cm across, smooth, somewhat succulent, pale brown with faint elliptical paler spots. Lamina 120 cm across, highly dissected, the rachises winged beyond the basal branchings, the most proximal supernumerary leaflets very shortly stalked; leaflets closely set, elliptical to elongate elliptical, 3-25 cm long and 1.5-7 cm across, acuminate.²
INFLORESCENCE:
The inflorescence appears while the leaf is breaking down and matures shortly afterwards. Longest cataphyll 17 cm long, pale pink and white; peduncle 20 cm long and 1.8 cm across, smooth, dark purplish brown with scattered greyish brown elliptical spots. Spathe broader than long, triangular-ovate, 9 cm long and 13 cm across, strongly convolute, the limb and base not separated, the margin slightly revolute and the apex acute, outside white with pale pinkish flushed veins and a pinkish flush near the base, inside white, the base within smooth. Spadix sessile, longer than the spathe, 15.5 cm long; female zone subcylindric, dorsiventrally compressed, the apex slightly expanded, 3 cm long, 2.3 by 1.8 cm at the base and 2.5 by 1.6 cm at the apex, the flowers congested or touching; male zone urn-shaped, strongly dorsiventrally compressed, the apex slightly dilated and the base constricted, 3 cm long, 2.5 by 2.2 cm at the base and 4.3 by 2.5 cm close to the apex, the flowers congested; appendix shortly and broadly conical, the base slightly dorsiventrally compressed and the apex slightly laterally compressed, 8.5 cm long and 5 cm across just above the base, tapering to the apex, the surface smooth with a few irregular shallow depressions, off-white, giving off a clear candy-like smell of organic acetates. Ovary globose to ovoid, about 2.5 by 2-2.5 mm, unilocular, pink; style very short, 0.5 mm long and 1.2 mm across, off-white; stigma depressed, 1.5 mm across and 0.5 mm high, minutely echinate, off-white. Male flowers of 3-4 stamens; stamens 1 mm long; filaments 0.5 mm long, entirely fused, off-white; anthers 0.5 mm long and 1-1.5 mm across, truncate, off-white, the pores apical and elliptical. Pollen striate.²
ECOLOGY:
The type came from damaged secondary evergreen forest on the slope of a limestone mountain at about 300 m.²
ETYMOLOGY:
From Latin tuberculum, “a small swelling”: the tuber is densely covered in thick fleshy warts. What makes them worth naming is that they sit independently of the root scars, unlike the annular thickenings other species carry.²
NOTES:
1. The scent is not carrion but organic acetates - fresh and candy-like. That places the species in a group around Amorphophallus yunnanensis, all of which smell the same way, and which it also resembles in spathe and spadix.²
2. Its flowering behaviour separates it from almost the whole genus. The inflorescence emerges as the leaf dies down and matures just after it. The nearest comparison is Amorphophallus ochroleucus, which flowers alongside the leaf just before the leaf cycle ends and which carries a conspicuous band of staminodes between the female and male zones.²
3. Several species in northern Vietnam, Laos and southern China depart from the ordinary Asian flowering cycle, and they do not belong to one lineage. Amorphophallus coaetaneus, Amorphophallus hayi, Amorphophallus rhizomatosus and Amorphophallus verticillatus all flower alongside the leaf long before it dies down.²
4. From the rest of the Amorphophallus yunnanensis group it differs in the strongly warted tuber, a spadix distinctly longer than the spathe, and a nearly all-white colouring.²
REFERENCES:
1. Plants of the World Online, Royal Botanic Gardens, Kew — Amorphophallus tuberculatus Hett. & V.D.Nguyen
2. Aroideana 29: 77 (2006) — protologue.
3. Alan Galloway — Amorphophallus tuberculatus, alangallowaybotanicals.com.