Globba, K. Larsen

Sangvirotjanapat, Sunisa, Denduangboriphant, Jessada & Newman, Mark F., 2019, A taxonomic revision of Globba subsect. Nudae (Zingiberaceae), European Journal of Taxonomy 503, pp. 1-37 : 3-10

Subsection Nudae K.Larsen

General morphology

The main distinguishing characteristics of G. subsect. Nudae are the lax conical inflorescence and flowers with four anther appendages. These differentiate this subsection clearly from G. sect. Globba and G. sect. Sempervirens, which also have four anther appendages, but have dense inflorescences with colourful, persistent bracts.

Description

Clump-forming herbs (10–) 40–80 cm tall, rarely to 1.5 m, leaning, with inflorescence turned upright. Bladeless leaf sheaths 3–5; ligule truncate to bilobed, glabrous or ciliate, light green with white margin; blades 5–11, oblong, elliptic or ovate, base obliquely obtuse, cuneate, apex acuminate to caudate, glabrous or strigose, sometimes with a grey patch or silver striate above, pubescent below. Inflorescence erect, lax, conical; peduncle 1–5(–15) cm long; rachis green, glabrous or pubescent; bracts and bracteoles caducous or persistent, oblong, elliptic, deltoid, 5–12 mm long, glabrous or pubescent, apex acute, green; cincinni numerous, lax or crowded; pedicel 0–5 mm long. Flowers 2.8–3.8 cm long; ovary 3–4 mm long, ellipsoid, green (⚥), ridged; calyx 3–5 mm long, infundibuliform, with lobes acute to acuminate, ciliate, green or yellow-green; floral tube 9–16 mm long, yellow-orange, pubescent, dorsal and lateral corolla lobes 6–7.5 mm long, elliptic, hooded, yellow, orange, orange-green; lateral staminodes 11–20 × 3–11 mm, obliquely obovate, oblong, bright yellow, yellow-orange or orange, apex rounded; labellum 6–8 × 5–7 mm, triangular, bilobed, yellow-orange, self-coloured, rarely ( G. aranyaniae Sangvir. & M.F.Newman sp. nov.) with red or brown spot at centre, base truncate, apex round, acute or obtuse; nectar tube 3–6 mm long; filament 23–30 mm long, yellow or yellow-orange; anther 1–2 mm long with 4 appendages, connective tissue, crest, and appendages orange, semi-translucent, crest ca 1 mm long (shorter in Ƌ), truncate; ⚥ appendages ca 3 mm long, acuminate, bifid, upper pair bigger, decurrent to connective tissue and crest, lower pair smaller; Ƌ appendages 3–4 mm long, acuminate, bifid to halfway, upper pair only slightly bigger than lower. Fruits 2.5–27 × 1–10 mm, ellipsoid or almost globose, longitudinally or shallow ridged, topped with persistent calyx. Bulbils produced at base of peduncle or tip of cincinni or protruding from leaf sheaths, spindle-shaped or obovate, tissue corky, producing one shoot.

Habitat

The substrate and ecological surroundings are found to relate to plant size. Plants in G. subsect. Nudae are mostly middle-sized, about 50–100 cm tall. Occasionally G. expansa Wall. ex Horan. , found in mixed evergreen montane forest, can grow to 1.5 m tall while G. lithophila Sangvir. & M.F.Newman sp. nov., which grows on limestone, is a miniature plant, only 10 cm tall. The most variable species is G. insectifera Ridl. , which is large or small depending on the conditions of the dry or the rainy season which determine the production of inflorescence shoots or leafy shoots.

Rhizome

Small, globose, about 3–5 cm in diameter. In one growing season, 5–8 rhizomes can be produced in a moniliform arrangement. The root tubers are spindle-shaped or elongate and function in food storage during the dormant period.

Leafy shoots

Pseudostem consisting of enfolded leaf sheaths. At the base there are 3–5 bladeless sheaths which are usually darker. The ligule is membranaceous, truncate to bilobed, light green with paler or white margin. Normally, ligules of this subsection do not vary greatly but, in the case of G. lancangensis Y.Y.Qian , the ligule appears node-like by embracing the axis of the leafy stem. This is a diagnostic difference between G. lancangensis Y.Y.Qian and G. insectifera Ridl. All leaf blades are arranged distichously, the lowest one smallest then becoming larger towards the apex. A few species have silver striations along the midrib, for instance G. expansa Wall ex Horan. and G. lithophila sp. nov. There is almost always an indumentum on both sides of the leaf blade which may be dense on the midrib and veins above but more evenly spread below. It should be noted that G. expansa Wall. ex Horan. is the sole species having a glabrous blade above. Globba flagellaris K.Larsen is unique as horizontal shoots protrude from the rhizome at an early stage, looking like flagella. This characteristic is reflected in its specific epithet ( Larsen 1977).

Inflorescence

Terminally produced (on a leafless shoot in G. insectifera ), erect, and lax. The overall shape is conical consisting of many cincinni arranged spirally. The main rachis and cincinni elongate greatly during flowering. The lowest cincinnus is the longest one becoming shorter toward top of inflorescence. The rachis is rather short when it is young then may elongate with age. Bulbils may be produced on the rachis at the end of the period of growth. The cincinni are held at nearly 90º to the rachis and are subtended by green, glabrous or pubescent bracts which are very small and caducous, rarely seen on herbarium specimens. The flowers are produced in two rows at the apex of the cincinni, each flower subtended by a bracteole which is usually the same shape as the bract. We recognise two morphological types of cincinnus, lax and crowded, which can be distinguished by the bracteole and flower scars on the cincinni. Lax cincinni may be elongate with a very short pedicel (e.g., G. expansa , Fig. 1A ) while crowded cincinni may have long pedicels closely packed (e.g., G. flagellaris and G. lithophila sp. nov., Fig. 1B ).

Species in this subsection are often misidentified because they show considerable similarity of habit and inflorescence structures. The flowers, bracts and bracteoles also easily fall so most herbarium specimens look alike. In this study, the most taxonomically informative character in the key to species is the crowded or lax cincinni. This character is effective and consistent when examining herbarium specimens without flowers but with good details on their labels. There is only one species, G. aranyaniae sp. nov. that shows both cincinnus types but their distribution areas do not overlap.

Flower

For reliable identification to species, the flower must be seen. Flower colour seems to be a variable character while, on the other hand, the yellow and orange tone of flowers in this subsection is clearly different and useful for classification in many cases. A red or brown spot on the labellum is quite common in other groups of Globba but, in G. subsect. Nudae , G. aranyaniae sp. nov. is unique in having a spot ( Fig. 2A ).

Andromonoecy

Monoecy is rare in the Zingiberaceae , having been reported in only a few species. Siphonochilus aethiopicus (Schweinf.) B.L.Burtt , an African ginger, shows gynomonoecy in which hermaphrodite and female flowers are produced on the same plant ( Gordon-Gray et al. 1989), while Alpinia sect. Monopleura K.Schum. and Alpinia sect. Myriocrater K.Schum. are considered andronomoecious with hermaphrodite and male flowers on the same plant ( Burtt & Smith 1972). Our investigations of the reproductive biology of G. section Nudae ( Sangvirotjanapat et al. 2017b) show that andromonoecy occurs as a synapomorphic character of both subsections. The hermaphrodite (⚥) and functionally male (Ƌ) flowers are in the same inflorescence but on separate cincinni, ⚥ flowers arising only on the two to four proximal cincinni. The fact that two floral types occur together has great taxonomic relevance because it has led earlier authors to recognise the flower types as different species. The differences of morphology between the floral types are highlighted below with an asterisk (*) and shown in Fig. 3 .

Floral size*

The Ƌ flower is smaller than the ⚥ flower and has a shorter floral tube.

Ovary and ovules*

These are strikingly dissimilar between the floral types. The ovary of the ⚥ flower is well developed, ellipsoid and longitudinally ridged with fully developed ovules inside. By contrast, the Ƌ flower has a greatly reduced ovary about 1 mm long with aborted ovules inside.

Calyx

Infundibuliform, trilobed, two of the lobes smaller than the other, with acute or acuminate lobes.

Epigynous nectaries or stylodes

All species of Globba have two linear epigynous nectaries above the ovary. Nectar is secreted into the floral tube towards the nectar tube.

Floral tube*

A narrow tube, about 1 mm in diameter. The outer surface is pubescent. Within an inflorescence, the ⚥ flower has a longer and more sharply curved floral tube than the Ƌ flower.

Dorsal and lateral corolla lobes

Hooded, elliptic, oblong or obovate, the dorsal one slightly bigger than the laterals. At anthesis, the lateral corolla lobes are usually concealed by the lateral staminodes or labellum but, in G. lithophila sp. nov., the lateral staminodes are rather narrow so the lateral corolla lobes can be seen clearly. The outer surface of the lobes is slightly pubescent and the colour is the same as the other parts but green tinted.

Lateral staminodes

All gingers possess staminodes derived from stamens. The tribe Globbeae is characterised by its free lateral staminodes and labellum. As for Globba , the lateral staminodes are attached above the lateral corolla lobes and are conspicuous, flat and patent. The shape can be oblong or obovate. All these differ from other sections in which the lateral staminodes are not as prominent.

Nectar tube and labellum

We consider the labellum of Globba to be made up of two parts. The nectar tube is connected to the floral tube but the cavity inside it is larger. Along one side, it is fused to the filament. This tube holds the nectar and is the channel for the style to reach the tip of the flower. The apex of the nectar tube expands and reflexes to form the labellum which is always triangular, bilobed. The labellum is slightly thicker and

darker than the other floral organs. In pollination, it serves as a landing platform and the spot may be a nectar guide indicating the position of the nectar tube where the pollinator reward is found.

Filament

Long and arching with a groove for the style in the lower part. In this paper, the measurement of the filament is calculated from the point of fusion with the nectar tube to the anther sac. This makes the length seem longer than is noted in the literature. Traditionally, only the part of the filament which extends from the labellum is measured. An approximate conversion can be made by adding or subtracting the length of the nectar tube.

Anther

Consisting of two thecae, each with loculicidal dehiscence along its entire length.

Anther appendages*

Both floral types have four-appendaged flowers. The appendages of this subsection consist of an upper and a lower pair of triangular appendages. They are fused at the base while the tips are completely free from each other. Consequently, the number of appendages when looking at the base is two while, at the tip, it is four. The ⚥ flower has larger appendages which occupy the whole length of the anther. The appendages are deeply bifid, and the upper pair is decurrent to the crest ( Fig. 3C ). The appendages of the Ƌ flower are split half-way with their bases fused together like a swallow’s tail. The anther crest is much less prominent in the Ƌ flower than in the ⚥ flower ( Fig. 3D ). This difference in size was first mentioned by Smith (1988) but she noted that the smaller crest may have been an effect of dehydration.

Style

Filiform, as long as the flower, the tip near the stigma held in position by the anther thecae.

Stigma*

In the ⚥ flower, bigger and completely full of stigmatic fluid to promote germination of pollen tubes.

Fruit

Ellipsoid and ridged in G. subsect. Nudae , except in G. lancangensis which has nearly globose and shallowly ridged fruits. The apex of the fruit in Globba always bears a persistent calyx.

Seed

Brown, globose to ovate, about 2–3 mm in diameter with a praemorse aril attached at the hilum. The surface is hairy ( Fig. 1C and Fig. 7G ). There are no seed characters which allow the species of this subsection to be differentiated.

Bulbil

A vegetative propagule, produced late in the growing season, before the plant goes dormant in the dry season ( Fig. 1D ). Generally, it is a corky tissue with one shoot but G. flagellaris , which grows in moist areas, has a prolonged shoot and the corky part is scarcely visible ( Fig. 7K ).

Key to the species

1. Flowers lax; bracteoles caducous.………………………………………………..…………………2 – Flowers crowded at tip of cincinni; bracteoles usually persistent on cincinni, packed with pedicels....5

2. Flower yellow-orange; labellum with red or brown spot at centre; limestone bedrock near streams .. ............………………………………...………….. G. aranyaniae Sangvir. & M.F.Newman sp. nov.

– Flower pure orange, bright yellow or primrose; labellum without spot; evergreen forest or open areas in dipterocarp forest ......……………….…………….........…………………………………3

3. Lateral staminodes oblong to narrowly obovate, 11–13 × 3–5 mm, yellowish orange; leafy stem to 150 cm; leaf glabrous above ......................................…. G. expansa Wall. ex Horan.

– Lateral staminodes obovate, ca 20 × 11 mm, bright yellow or primrose; leafy stem to 80 cm; leaf strigulose above …..……………...............................................................................……………..4

4. Flower lemon or bright yellow; bracts deltoid, 0.5–4 × 1–2 mm; fruit ellipsoid, longitudinally ridged; leaf sheaths smooth along the leafy stem; inflorescences produced on separate shoots and at tip of leafy shoots …..................................................................................… G. insectifera Ridl.

– Flower primrose or pale yellow; bracts lanceolate, 1.5–7 × 1–2 mm; fruit almost globose, shallowly ridged; leaf sheaths node-like along the leafy stem; inflorescences only produced at tip of leafy shoots …….....................................................................… G. lancangensis Y.Y.Qian

5. Flower yellow-orange; labellum with red or brown spot at centre; lateral staminodes obliquely obovate ………................…………………………. G. aranyaniae Sangvir. & M.F.Newman sp. nov.

– Flower pure orange; labellum without spot; lateral staminodes oblong or obliquely obovate...6

6. Lateral corolla lobes easily seen; lateral staminodes oblong, to 5 mm wide; lithophyte in small pockets of soil over limestone ……………..........……….… G. lithophila Sangvir. & M.F.Newman sp. nov.

– Lateral corolla lobes covered by labellum or lateral staminodes; lateral staminodes broad, obovate, 5–9 mm wide; terrestrial ……………...............................…………………………………………..7

7. Labellum as long as lateral staminodes, 10–12 mm long; inflorescence 10–30 × 7–18 cm; growing in wet areas; flagella produced …..........................................… G. flagellaris K.Larsen

– Labellum longer than lateral staminodes, 19–20 mm long; inflorescence 5–11 × 5–12 cm; growing in somewhat dry areas or bamboo forest; without flagella ………………...................................... .............................................................…….…… G. macrochila Sangvir. & M.F.Newman sp. nov.

Figures

Fig. 1. Cincinnus morphology in G. subsect. Nudae K.Larsen. A. Lax cincinni (M.F. Newman 2561 leg.). B. Crowded cincinnus (S. Sangvirotjanapat 642 leg.). C. Seeds (M.F. Newman 2561 leg.); the area in the inset is indicated by a white arrow. D. Bulbils (M.F. Newman 2561 leg.). Drawings and photographs: S. Sangvirotjanapat.

Fig. 2. Globba subsect. Nudae K.Larsen. A. G. aranyaniae Sangvir. & M.F.Newman sp. nov. (S. Sangvirotjanapat 785 leg.). B. G. expansa Wall. ex Horan. (M.F. Newman 2561 leg.). C. G. flagellaris K.Larsen (M.F. Newman and JLS 2048 leg.). D. G. insectifera Ridl. (S. Sangvirotjanapat s.n. leg.). E. G. lithophila Sangvir. & M.F.Newman sp. nov. (M.F. Newman 2576 leg.). F. G. macrochila Sangvir. & M.F.Newman sp. nov. (S. Sangvirotjanapat 795 leg.). Photographs: S. Sangvirotjanapat.

Fig. 3. Parts of the hermaphrodite and functionally male flowers. A. ç flower. B. Ƌ flower. C. Anther appendages of ç flower. D. Anther appendages of Ƌ flower. Drawing: S. Sangvirotjanapat from M.F. Newman 2561 leg. (G. expansa Wall. ex Horan.).

Fig. 7. A–G. G. expansa Wall. ex Horan. A. Habit. B. Inflorescence. C. ç (above) and Ƌ (below) appendages. D. ç flower. E. Ƌ flower. F. Ligule. G. Mature fruit with seed (M.F. Newman 2561 leg.). H–K. G. flagellaris K.Larsen. H. Habit. I. ç flower. J. Fruit. K. Bulbils (M.F. Newman 2581 leg.). Photographs: S. Sangvirotjanapat.