AMORPHOPHALLUS OPERTUS
PROTOLOGUE: Amorphophallus opertus Hett., published in Blumea 39: 267 (1994).
Amorphophallus opertus Hett., spec. nov. Ab Amorphophallus koratensi Gagnep. in stigmatibus non lobatis ovariis unilocularibus differt. - Typus: Hetterscheid H.AM.141-T (L holo; spirit coll.), 9-V-1994, cult. Hort. Bot. Leiden ex Vietnam, Dac Lac Prov., s. loc. (orig. coll. A. Kuznetsov, 1992).
DISTRIBUTION: Vietnam: Vietnam.
DISTRIBUTION NOTE: Vietnam: Dak Lak Province (the type) and Lam Dong Province - the Nam Cat Tien reserve.².
SPECIES DESCRIPTION:
Tuber depressed, up to c. 10 cm in diam., c. 6 cm high, weighing up to c. 500 g, young parts orange-brown, otherwise dark brown, annually developing numerous, rhizomatous offsets, these up to 7 cm long and c. 1.5 cm in diam. Leaf solitary; petiole up to c. 100 cm long, c. 2 cm in diam., surface scabrous, background colour blackish green to nearly black, often mixed with a dense pattern of olive green, or small white spots and with larger, scattered, elliptic-oval, pale whitish green spots, the largest ones with a dark centre, surface with an oily sheen; lamina up to c. 110 cm in diam., rhachises naked or very narrowly winged; leaflets elliptic, elliptic-lanceolate, or lanceolate, 8-27 cm long, 4-8.5 cm in diam., subacute, upper surface green.²
INFLORESCENCE:
Inflorescence solitary, short peduncled; peduncle 3 cm long, 1.2 cm in diam., entirely subterranean, moderately verrucate, dirty white with small, confluent, greyish or greyish greenish spots; spathe opening only at the top, very turgid, broadly cylindric, transversely oval, 17 cm long, 21 cm in diam., lower 10 cm strongly convolute, base broadly truncated, top acute, base and limb hardly differentiated by only a shallow depression, clearest at the backside at c. 5 cm from the base, margin around the opening sinuous, outside base near peduncle off-white with a few greyish spots, then with a greyish brown background colour with numerous small, very dark green spots and scattered, slightly larger dirty whitish spots, basal and central part of the backside glossy, inside lower half deep purple, upwards with irregular, diffuse whitish spots, upper half with a basal dirty pale yellowish greenish zone, the remainder dirty brown, upper margin bright emerald-green, base within shallowly verrucate. Spadix sessile, shorter than spathe, 10 cm long, nearly entirely hidden by spathe but for the upper part of the appendix; female zone slightly conic, 3 cm long, 2 cm in diam. at the base, 1.7 cm in diam. at the top, flowers congested; male zone cylindric, base slightly constricted, 2.7 cm long, 1.8 cm in diam., flowers congested; appendix conic, 4.3 cm long, 1.8 cm in diam. at the base, off-white, top subacute, base consisting of separated, rod-shaped staminodes, upwards fusing to form the appendix wall, leaving deep, narrow depressions in between, upper half transversely rugulose, developing a powerful gas-stench at female anthesis. Ovaries depressed, angulate, 3 mm in diam., 2 mm high, unilocular, base whitish, rest reddish purple; style sturdy, slightly conic, 2 mm long, 1 mm in diam. at the base, 0.8 mm in diam. at the top, reddish purple; stigma conic, circular in cross section, 1.5 mm in diam., 1 mm high, entire but with a one-sided, transversely elongate, shallow depression, mostly directed to the top of the spadix, surface densely echinulate, off-white. Male flowers consisting of 2-4 stamens; stamens off-white, 3 mm long, 1-1.5 mm in diam.; filaments 0.5 mm long, connate; anthers 2.5 mm long, truncated, pores apical, marginal, elongate, elliptic at anthesis, connective slightly raised. Pollen psilate, orange.²
ECOLOGY:
Found in open forest²
PROPAGATION:
Propagated in water successfully
ETYMOLOGY:
From Latin opertus, “covered,” “concealed,” or “enclosed,” referring to the remarkable floral chamber. The thick-walled spathe opens only near its apex and almost completely encloses the spadix, leaving little more than the upper part of the appendix visible.
NOTES:
1. Diagnosis: it differs from Amorphophallus koratensis in the unlobed stigmas and unilocular ovaries.²
2. Amorphophallus opertus is very similar to Amorphophallus koratensis and Amorphophallus scaber. From the first it differs primarily in having an entire stigma, a unilocular ovary and elliptic-lanceolate leaflets; from Amorphophallus scaber it differs in the same characters and in being much smaller.²
3. It belongs to an informal group with Amorphophallus hirsutus, Amorphophallus koratensis, Amorphophallus paeoniifolius and Amorphophallus prainii, recognised by tubers with large, annulate, thickened root scars, elongate offsets, large lobed stigmas, very long narrow anthers and often scabrate-echinate petioles.⁴
4. The peduncle is entirely subterranean and the spathe opens only at the very top, so that almost the whole spadix stays hidden inside it - all that shows is the tip of the appendix. The appendix develops a powerful gas-stench at female anthesis.²
REFERENCES:
1. Plants of the World Online, Royal Botanic Gardens, Kew — Amorphophallus opertus Hett.
2. Blumea 39: 267 (1994) — protologue.
3. Alan Galloway — Amorphophallus opertus, alangallowaybotanicals.com.