Bambusa gurgandii K. M. Wong & M. H. Diep, 2015

Wong, Khoon Meng & Diep, My Hanh, 2015, Bambusa gurgandii K. M. Wong & M. H. Diep (Poaceae, Bambusoideae), a new species of bamboo from Vietnam, Candollea 70 (2), pp. 211-218 : 215-216

Bambusa gurgandii K. M. Wong & M. H. Diep , spec. nova ( Fig. 1-2 ).

Typus: VIETNAM. Prov. Binh Duong: Ben Cat, Phu An Bamboo Village , cultivated as Accession 45 (introduced from Hue Province, Thua Thien, Nam Dong, Khe Tre, 16°10’53”N 107°43’12”E, 350 m alt.), 24.XI.2014, M. H. Diep, C. K. Le, J. Gurgand et al. MH 100 (holo-: SING [ SING0210902 shoot & leafy branch, SING0210903 culm sheath, SING0210904 inflorescence and leafy branch, SING0202907 pseudospikelets in spirit]! ; iso-: G!, IBSC!, K!, P!, PBB!, US!, VNM!).

Bambusa gurgandii resembles B. polymorpha Munro in having conspicuously bristly-auriculate culm sheaths with erect blades, conspicuous laterally extending and long-bristly leaf-sheath auricles, glabrous lemmas, glabrous palea keels and maroon anthers. It differs from B. polymorpha in its sparsely pale brown to medium brown or black hairy culm sheaths, glabrescent and slightly white-waxy mid-culm internodes, glabrous leaf blades, and blunt anther apices. In contrast, B. polymorpha has densely white-hairy culm sheaths, conspicuously pale appressed-hairy and intensely white-waxy mid-culm internodes, hairy lower leaf surfaces, and apiculate anther apices.

Clumping bamboo to c. 15 m tall. Culms plain green, to 10 cm diameter, quite stiffly erect and apically only slightly arching, with well-spaced culms about 10-30 cm apart. Culm internodes with a conspicuous covering of appressed pale hairs all over the basal few internodes, this becoming scantier and more restricted to the internode base towards mid-culm, with a consistent narrow ring of dense appressed pale hairs just above each node; and a slight white-waxy bloom all over. Culm sheaths on mature culms 22-32 cm long, mainly pale green, infused with yellowish green at the top of the sheath proper; with scattered pale brown to medium brown or black appressed hairs and a slight white-waxy bloom all over the back; basal part at the sheath insertion with a 2-3 mm narrow ring-like band of dense spreading medium to dark brown hairs 2-3 mm long; blade 5.5-24 cm long, broad to narrowly triangular, erect but loosely held (not tightly appressed) against the next sheath or internode, medium green, with a slight white-waxy bloom on the outer (abaxial) side, with fine 2-4 mm long sinuous pale brown bristles at the base of the margin, the blade base with a few corrugations as it continues with only slight constriction into laterally elongate, spreading lobe-like auricles; auricles 5-10 mm high, protruding to 1-1.5 cm laterally from the sheath margin and slightly downcurved at the end, purplish brown, with sinuous bristles on the edge 5-7 mm long; ligule a leathery low subentire rim 1-2.5 mm high with 2-5 mm long narrowly triangular teeth on the margin. Branch buds solitary at each branching node, the prophyll broadly dome-shaped with fused margins and resembling a broad hood around the bud. Branches at mid-culm with the primary axis dominant in size and length with 2-several higher-order branches from its base, less often with only the primary axis developed. Branch leaves mostly c. 10-23 cm long, to 1.5-2.6 cm broad, dark green, slightly glaucous on the lower (abaxial) surface, glabrous on both surfaces; auricles conspicuous laterally spreading narrow lobes 0.5-1 mm high and 3-5 mm long, slightly downcurved at the end, margins with fine spreading bristles 5-7 mm long; ligule inconspicuous; sheath glabrous; the abaxial side of the sheath apex developing a scale-like callus 1-2 mm long with subentire-erose margin. Inflorescences iterauctant, with the basic flower-bearing unit consisting of ellipsoid pseudospikelets bearing prophyllate buds at their base and the spikelet proper distal to these, the prophyllate buds themselves developing into new pseudospikelets. Pseudospikelets slightly flattened, when mature to 2-3.8 cm long, 7-9 mm wide; each with 1-3 bracts subtending prophyllate buds, 1 empty glume, 5-9 perfect flowers, and 1-2 terminal vestigial flowers consisting of an empty lemma or a lemma and palea only; rachilla internodes 1-1.5 mm long, glabrous and disarticulating between flowers. Flower with lemma 12-16 mm long, 18-21-veined, back glabrous and pale green, margins glabrous, apex with a short cusp c. 1 mm long; palea 12-15 mm long, 2-keeled, the back strongly sulcate, 7-veined, glabrous, the apex acuminate to very slightly cleft, the keel thickened, glabrous, the wings 4-veined, glabrous except for the minutely ciliate apical part including the margins; lodicules 3, rounded, c. 1 mm diameter developing to 2-3 mm diameter in the mature flower, thin-hyaline and delicate, bearing 1 mm long cilia on the margins; stamens 6, filaments free, 4-5 mm long developing to 10-18 mm long when mature, white turning brown, anthers 8-9 mm long when extruded, the apical part of the connective blunt and bearing a tuft of 3-5 spreading minute spines, the thecae maroon turning brown; ovary c. 1 mm long, ovoid, with a thickened apex bearing long hairs 0.5-1 mm long, style 0.5-1.5 mm long bearing 3 linear stigmas c. 3 mm long with short hairs all over. Fruit a caryopsis, obovoid, 8-12 mm long, 4-4.5 mm across, somewhat 3-angled with the dorsal (back) portion strongly sulcate and smooth, the apex conspicuously thickened and hairy, the ventral surfaces smooth to minutely tuberculate.

Etymology. ‒ This new species is named for Jacques Gurgand ( Fig. 3 ), a firm associate of the Phu An Bamboo Village with an extraordinary interest in the bamboos of Vietnam, who celebrated his 80th birthday in February 2015, and worked with the authors to elucidate the characters of this new bamboo species.

Conservation status. ‒ Bambusa gurgandii is known only from plants in cultivation, the extent of which has not been ascertained at the type locality in the Hue Province from where it was introduced. Its presence in other parts of Vietnam has also not been ascertained. It has so far not been documented in the better-known bamboo floras of South China and India, so even if it were indigenous to Vietnam, the new species is therefore assigned a preliminary status of “Data Deficient” [DD] following IUCN Red List Categories and Criteria ( IUCN, 2012).

Notes. ‒ In having conspicuous laterally spreading culmsheath auricles with long bristles, erect triangular culmsheath blades, as well as few-many-flowered, slightly flattened pseudospikelets often longer than 1 cm with elongate rachilla internodes, Bambusa gurgandii resembles the group of species including B. burmanica Gamble , B. farinacea K. M. Wong , B. nutans Wall. ex Munro , B. polymorpha , B. teres Buch. -Ham. ex Munro, and B. tulda Roxb. It is easily distinguished from B. polymorpha as explained in the diagnosis above. Furthermore, it differs from B. burmanica and B. teres in its blunt (not apiculate) anther apices and glabrous (not hairy) rachilla internodes; from B. farinacea in its maroon anthers with blunt apices bearing a cluster of minute spines (not yellow anthers with emarginate glabrous apices) and glabrous (not hairy) palea keels; from B. nutans in its glabrous (not hairy) lemma margins, blunt (not apiculate) anther apices and glabrous (not hairy) rachilla internodes; and from B. tulda in its glabrous (not fine-hairy) lemma margins, glabrous (not fine-hairy) palea keels, blunt anther apices with a cluster of minute spines (not emarginate anther apices without spines), and glabrous (not short-hairy) rachilla internodes.

Figures

Fig. 1. –Bambusa gurgandii K. M. Wong & M. H. Diep, general vegetative and pseudospikelet characters.A. Culm shoot; B. Culm node, showing a narrow ring of dense appressed pale hairs just above each node; C. Branch leaves with conspicuous laterally spreading, bristly sheath auricles; D. Part of flowering branch, showing pseudospikelets with extruded maroon anthers. [Photos: A: M. H. Diep; B-D: K. M. Wong]

Fig. 2. – Bambusa gurgandii K. M. Wong & M. H. Diep, pseudospikelet and floral characteristics. A. Pseudospikelet with, from base, two bracts subtending prophyllate buds, a single glume, eight perfect flowers visible, with the 9th perfect flower and 1-2 terminal vestigial flowers hidden by the 8th flower; B. Bract subtending a prophyllate bud; C. Prophyll of bud subtended by basal bract; D. Lowermost perfect flower in lateral view with lemma (l), palea (p) and rachilla segment (r); E. Palea, ventral view; F. Detail of palea apex; G. Lodicule complement; H. One of six anthers;I. Anther apex showing blunt connective and tuft of spines; J. Mature ovary; K. Caryopsis with sulcate dorsal side. [Drawing: K. M. Wong]

Fig. 3. – Jacky Gurgand holding dark-haired culm sheaths of the form of Bambusa gurgandii K. M. Wong & M. H. Diep known as “l ô đen”. [Photo: K. M. Wong]