Short Communication
Print
Short Communication
Describing terminologies and discussing records: More discoveries of facultative vivipary in the genus Hedychium J.Koenig (Zingiberaceae) from Northeast India
expand article infoAjith Ashokan, Vinita Gowda
‡ Indian Institute of Science Education and Research, Bhopal, India
Open Access

Abstract

The authors introduce the term facultative vivipary for the first time in gingers and elaborate on this reproductive strategy. Four new observations of facultative vivipary are reported in the genus Hedychium which were discovered during botanical explorations by the authors in Northeast India (NE India) over the past three years. The viviparous taxa are H. marginatum C.B.Clarke, H. speciosum var. gardnerianum (Ker Gawl.) Sanoj & M.Sabu (previously, H. gardnerianum Sheppard ex Ker Gawl.), H. thyrsiforme Buch.-Ham. ex Sm. and H. urophyllum G.Lodd. The authors also attempt to summarise the occurrence of vivipary in the family Zingiberaceae from published reports and to clarify a taxonomic misidentification in a previously known report of vivipary in Hedychium elatum.

Keywords

Facultative vivipary, gingers, Meghalaya, Nagaland, phenology, pseudovivipary, recalcitrant seeds

Introduction

Vivipary in plants is a heterogeneous term that describes a unique and rare reproductive strategy where seedlings are precociously produced while still on the maternal parent (Goebel 1905). With the discovery of several examples of germination on the parent plant in various angiosperm families, vivipary has become a biologically complex term because it now accommodates both sexual (true vivipary and cryptovivipary, see Elmqvist and Cox 1996) as well as asexual reproductive (pseudovivipary) strategies in plants (Farnsworth 2000).

True vivipary refers to vivipary sensu stricto and it is defined as penetration of a sexually reproduced embryo through the fruit pericarp and the resultant dispersal of this seedling (Cota-Sánchez 2004). Contrastingly, cryptovivipary is defined as vivipary wherein the seedling does not penetrate the fruit pericarp (Cota-Sánchez and Abreu 2007), while pseudovivipary is defined as production of apomictic or asexual propagules (like bulbils) on the parent plant (Law et al. 1983, Ofir and Kigel 2014). Thus sexually reproduced progeny (seed) is an integral part of the definition of vivipary and should not be confused with pseudovivipary which refers to production of apomictic or asexual plantlets or bulbils (Poulsen and Nordal 2005).

Within the family Zingiberaceae, vivipary is rarely discussed as an important reproductive strategy, except in Hedychium elatum R.Br. by Bhadra et al. (2013) (taxonomic misidentification discussed later). However, vivipary has been recorded in taxonomic descriptions such as in Camptandra latifolia Ridl. (Ridley 1899), in natural history observations (Hedychium gardnerianum Sheppard ex Ker Gawl.; Djeddour et al. 2012) and in pollination studies (Alpinia mutica Roxb.; Aswani and Sabu 2015). In contrast, pseudovivipary is very common in the form of bulbils and it has been recorded in at least six genera within Zingiberaceae: Alpinia Roxb., Boesenbergia Kuntze, Globba L., Hedychium J.Koenig, Larsenianthus W.J.Kress & Mood and Zingiber Mill. (Table 1). Interestingly, pseudovivipary (bulbil formation) was one of the key characters used to distinguish section Globba into two series by Schumann (1904) during the revision of Zingiberaceae, although recent molecular studies have not addressed the role of bulbil as an important character defining clades (see Williams et al. 2004).

Summary of published and personal records where vivipary sensu lato were identified within Zingiberaceae. All Globba synonyms following Williams et al. (2004), Newman and Pullan (2007), WCSP (2018).

Vivipary recorded in Zingiberaceae Type of vivipary Reference(s)
Alpinia Roxb.
A. mutica Roxb. Vivipary* Aswani and Sabu 2015
A. purpurata (Vieill.) K.Schum. Pseudovivipary Dekkers et al. 1991
Boesenbergia Kuntze
B. parvula (Wall. ex Baker) Kuntze Pseudovivipary Mood et al. 2016
B. pulcherrima (Wall.) Kuntze Pseudovivipary Aishwarya and Sabu 2015
Camptandra Ridl.
C. latifolia Ridl. Vivipary* Ridley 1899
Curcuma L.
C. coriacea Mangaly & M.Sabu Vivipary* Leong-Škorničková 2007
Globba L.
G. aurantiaca Miq. Pseudovivipary Ridley 1899
G. bicolor Gagnep. Pseudovivipary Gagnepain 1901
G. bulbifera Roxb. Pseudovivipary Horaninow 1862, Baker 1894
G. cambodgensis Gagnep. Pseudovivipary Gagnepain 1901
G. cernua Baker Synonym: G. brachycarpa Baker or G. trachycarpa Baker Pseudovivipary Schumann 1904, Box and Rudall 2006
G. chinensis K.Schum. Pseudovivipary Schumann 1904
G. colpicola K.Schum. Pseudovivipary Schumann 1904
G. lancangensis Y.Y.Qian Pseudovivipary Zhou et al. 2007
G. leucantha Miq. Synonym: G. pallidiflora Baker ex Ridl. Pseudovivipary Ridley 1899
G. marantina L. Synonyms: G. barthei Gagnep., G. ectobolos K.Schum., G. heterobractea K.Schum., G. strobilifera Zoll. & Moritzi Pseudovivipary Horaninow 1862, Gagnepain 1901, Liu et al. 2004, Williams et al. 2004, Box and Rudall 2006
G. multiflora Wall. Synonym: G. rubromaculata J.Lal & D.M.Verma Pseudovivipary Baker 1894, Schumann 1904, This paper
G. parva Gagnep. Pseudovivipary Gagnepain 1901, Schumann 1904
G. pendula Roxb. Synonyms: G. calophylla Ridl., G. kingii Baker, G. panicoides Miq., G. stenothyrsa Baker, G. wallichii Baker Pseudovivipary Ridley 1899
G. platystachya Baker Pseudovivipary Baker 1894
G. racemosa Sm. Synonyms: G. clarkei Baker, G. hookeri C.B.Clarke ex Baker Pseudovivipary Baker 1894, Schumann 1904
G. ranongensis Picheans. & Tiyawora. Pseudovivipary Picheansoonthon and Tiyaworanant 2010
G. schomburgkii Hook.f. Synonym: G. globulifera Gagnep. Pseudovivipary Gagnepain 1901, Schumann 1904
G. sessiliflora Sims Synonyms: G. canarensis Baker, G. careyana Roxb., G. ophioglossa Wight Pseudovivipary Horaninow 1862, Baker 1894, Schumann 1904
G. substrigosa Synonym: G. aphanantha K.Larsen Pseudovivipary Larsen et al. 1998
G. unifolia Ridl. Pseudovivipary Holttum 1950
G. ustulata Gagnep. Pseudovivipary Gagnepain 1901
Hedychium J.Koenig
H. greenii W.W.Sm. Pseudovivipary Smith 1911
H. marginatum C.B.Clarke Facultative vivipary This paper
H. speciosum var. gardnerianum (Ker Gawl.) Sanoj & M.Sabu Synonym: H. gardnerianum Sheppard ex Ker Gawl. Facultative vivipary Djeddour et al. 2012, Bhadra et al. 2013, This paper
H. thyrsiforme Buch.-Ham. ex Sm. Facultative vivipary This paper
H. urophyllum G.Lodd. Facultative vivipary This paper
Hornstedtia Retz.
H. scyphifera J.Koenig ex Steud. Vivipary* Leong-Škorničková (pers. comm.)
Larsenianthus W.J.Kress & Mood
L. careyanus (Benth. & Hook.f.) W.J.Kress & Mood Pseudovivipary Mibang and Das 2017, Poulsen (pers. comm.), This paper
Zingiber Mill.
Z. puberulum Ridl. Pseudovivipary Leong-Škorničková (pers. comm.)
Z. singapurense Škorničk. Pseudovivipary Leong-Škorničková et al. 2014

The genus Hedychium (more than 80 species, see Sanoj 2011) is native to the Indian subcontinent, China, Southeast Asia (mainland and maritime) and Madagascar (Kress et al. 2002, Newman et al. 2004, Newman and Pullan 2007, Sanoj et al. 2013, WCSP 2018). The highly speciose regions are identified to be NE India (Arunachal Pradesh, Manipur, Meghalaya, Mizoram, Nagaland and Sikkim), Southwest China (Yunnan), Myanmar, Thailand, Borneo and Java (Holttum 1950, Sirirugsa and Larsen 1995, Gao et al. 2008, Sarangthem et al. 2013). The plant habit ranges from terrestrial to epiphytic as well as lithophytic and each plant has a perennial rhizome which bears new ramets annually. Each ramet gives rise to a terminal inflorescence (known as thyrse) which consists of primary inflorescence bracts that hold flowers in cincinni (Kirchoff 1997). Two main types of inflorescence bracts are identified in Hedychium- imbricate (where bracts are broad and overlapping, hiding the rachis) and folded (where bracts are narrow and fold partially or completely to enclose the flowers, leaving rachis visible, Holttum 1950). The flowers are hermaphroditic, characterised by reduced petals and petaloid staminodes. The fruit is a septifragal capsule, light to dark green when young and changes to yellow with age (Fig. 1A). It splits open into three fleshy lobes, deep yellow or orange internally, with seeds arranged as in axile placentation. Mature seed is brown or black, covered by an aril which is either deep red or bluish-violet (in H. hookeri Baker, Srivastava 1984; fig. 1B). Frugivorous birds (Orchard 1973, Larsen et al. 1998) and rodents (Ridley 1899, Shiels 2011) are major dispersers of Hedychium seeds.

Figure 1. 

Septifragal capsule of Hedychium. A Unripe fruit of H. marginatum B Ripe fruit of H. spicatum (seeds can be seen covered by aril). Photographed by A. Ashokan.

Although the name Hedychium is more than 230 years old (Koenig 1783), the report of vivipary in this genus is very recent (Djeddour et al. 2012, Bhadra et al. 2013). The first vivipary in Hedychium was detailed by Bhadra et al. (2013) in H. elatum from Kalimpong, on the way to Darjeeling (West Bengal, India) although it had already been reported in Djeddour et al. (2012). Here, four new observations are reported of facultative vivipary in the genus Hedychium: H. marginatum, H. speciosum var. gardnerianum, H. thyrsiforme and H. urophyllum. The taxonomic misidentification in Bhadra et al. 2013 is also reported and it is suggested that vivipary was not observed by them in H. elatum but the plant observed by them could likely be H. speciosum var. gardnerianum. Since voucher information is not available from Bhadra et al. (2013), their published images were used to assign an identity to the plant identified by them as H. elatum. Based on a published image (figure 1A in Bhadra et al. 2013) and the characters listed here in Table 2, it is clear that the species they reported cannot be H. elatum. Since voucher specimens or high resolution images are critical in species-level identification in Hedychium, it is suggested that the two likely species illustrated by Bhadra et al. in their figure 1A are either H. gracile Roxb. or H. griffithianum Wall. (Wallich 1853) based on the inflorescence shape and delicate nature of the inflorescence bracts and flowers, which are characteristics to these species (Table 2). Further, the plant shown in figures 1B–H of Bhadra et al. is identified as H. speciosum var. gardnerianum (Ker Gawl.) Sanoj & M.Sabu. Therefore, the plant image shown with vivipary (figures 1B–H in Bhadra et al. 2013) is identified as H. speciosum var. gardnerianum because of the taxonomic description given by Bhadra et al. as “leaves white pulverulent beneath” which is characteristic of H. speciosum var. gardnerianum (Baker 1894).

List of characters used to resolve the taxonomic identifications of plants in Figures 1A–H in Bhadra et al. 2013. Characters in bold were used by them to describe H. elatum, which are characteristics of either H. gracile or H. griffithianum or H. speciosum var. gardnerianum.

Taxon Nature of lamina (abaxial) Midrib type (adaxial) Inflorescence height (cm) Inflorescence density Colour (labellum and filament) Length of corolla segments (cm)
H. elatum not pulverulent faintly grooved >30 dense to moderately dense labellum pinkish-white with red centre; filament reddish-pink 3.5
H. gracile not pulverulent faintly grooved 5–10 lax to moderately dense labellum creamy white with pale red base; filament bright red 2.5
H. griffithianum not pulverulent faintly grooved 15–22 moderately dense labellum creamy white with pale red base; filament bright red 2.5
H. speciosum var. gardnerianum pulverulent deeply grooved 30–45 dense to moderately dense labellum lemon yellow; filament bright red 2.5–3.6

For taxonomic clarity, the key morphological and ecological characters of the Hedychium taxa) are listed below where facultative vivipary has been observed. Voucher information is provided below as: collector name, voucher number, herbarium deposited.

1. Hedychium marginatum C.B.Clarke (Figs 2A–B, 3A; V. Gowda, VG-NL1899, BHPL)

Plant terrestrial, up to 1.5 m tall. Inflorescence conical; bracts imbricate; cincinni 3–6 flowers. Flowers orange-yellow, fragrant. Capsule elliptic, green and minutely hairy. Seeds many; aril red. The viviparous individual (bearing at least 10 seedlings on its dried infructescence) was observed along the Mokokchung-Tuensang Road, Mokokchung, Nagaland (26°19'59"N; 94°32'50"E) in August 2017 (Fig. 4).

Figure 2. 

Facultative vivipary in Hedychium. A–B Hedychium marginatum C–D H. speciosum var. gardnerianum, E&F. H. thyrsiforme, G&H. H. urophyllum. Photographed by A. Ashokan & N.S. Prasanna (E&F).

It is very common in the Indian states of Manipur and Nagaland (Clarke 1890, Baker 1894, Sanoj 2011).

Flowering period: August to October; fruiting from September to November.

2. Hedychium speciosum var. gardnerianum (Ker Gawl.) Sanoj & M.Sabu (Figs 2C, D, 3B; A. Ashokan, VG-ML1660, BHPL)

Plant terrestrial, up to 2.5 m tall. Inflorescence cylindrical; bracts folded, folding supervolute; cincinni 2 flowers. Flowers lemon-yellow with bright red stamen, highly fragrant. Capsule oblong, green and glabrous. Seeds many; aril red. The viviparous individuals were found growing along the Shillong-Dawki Road in the East Khasi Hills district, Meghalaya (25°22'25"N; 91°52'37"E) in August 2016 and 2017 (Fig. 4).

It has a wide distribution range covering Eastern Himalaya and NE India, especially the Indian states of Arunachal Pradesh and Meghalaya (Edwards 1823, Roscoe 1828).

Flowering period: July to October; fruiting from September to November.

3. Hedychium thyrsiforme Buch.-Ham. ex Sm. (Figs 2E–F, 3C; N.S.Prasanna, VG-MZ2201, BHPL)

Plant terrestrial, up to 1.5 m tall. Inflorescence pyramidal; bracts folded, folding supervolute; cincinni 3–8 flowers. Flowers white, mildly fragrant. Capsule oblong, green and glabrous. Seeds many; aril red. The viviparous individual (bearing one seedling on its dried infructescence) was observed in Aizawl, Mizoram (23°43'48"N; 92°43'52"E) in July 2017 (Fig. 4).

It grows very commonly in the Indian state of Mizoram. It was originally described from Nepal (Smith 1811).

Flowering period: August to October; fruiting from September to November.

Figure 3. 

Inflorescence. A Hedychium marginatum B H. speciosum var. gardnerianum C H. thyrsiforme D H. urophyllum. Photographed by A. Ashokan.

4. Hedychium urophyllum G.Lodd. (Figs 2G–H, 3D; A. Ashokan, VG-ML1612 & 1725, BHPL)

Plant terrestrial, up to 2.2 m tall. Inflorescence conical; bracts imbricate; bracts are found to retain water; cincinni 2–4 flowers. Flowers bright yellow, highly fragrant. Capsule elliptic, dark green and glabrous. Seeds many; aril red. The viviparous H. urophyllum was growing in a mixed pine forest at Sanmer along the Shillong-Elephant Falls Road, East Khasi Hills district, Meghalaya (25°32'47"N; 91°50'16"E) in June 2015 and August 2016 (Fig. 4).

Figure 4. 

Distribution records for facultative vivipary in Hedychium in NE India.

It is endemic to Meghalaya (Loddiges 1831, Sanoj 2011).

Flowering period: July to September; fruiting from September to November.

Discussion

During the three year study in NE India, four different Hedychium taxa showing vivipary have been identified: H. marginatum, H. speciosum var. gardnerianum, H. thyrsiforme and H. urophyllum. However, current observations of vivipary in Hedychium cannot be strictly identified as true vivipary or cryptovivipary (Elmqvist and Cox 1996, Cota-Sánchez 2004) since the fruit of Hedychium (septifragal capsule) dehisces before seed maturation while true vivipary requires the embryo to penetrate the fruit pericarp during germination. This makes the viviparous seed germination in Hedychium or gingers a case of “facultative vivipary”, which is introduced for the first time in gingers. The term “facultative vivipary” is proposed for the reproductive strategy observed in Hedychium since it represents the facultative nature of this reproductive strategy (occurs only when seeds are retained by bracts) as well as the viviparous nature of the germinating seed (seedling borne on the parent plant).

The factors leading to the incidence of facultative vivipary can be identified as a combination of climatic, ecological and physiological variables (Lee and Harmer 1980, Cox and Humphries 1993). In most Hedychium, flowering and fruiting coincide with the rainy season (an ecological trait shared amongst almost all Hedychium). The morphology of bracts in many Hedychium is such that the bracts can hold water. Thus the bracts provide a platform for the germination of the recalcitrant seeds by holding water which favours their germination. Further, these bracts are retained even after maturity of seeds thus facilitating their continued growth as seedlings. Thus, facultative vivipary may be a result of ‘failure to disperse’ either due to the structural hindrance imparted by the bracts or due to the absence of a disperser. The importance of facultative vivipary was not discounted as an important reproductive strategy that may facilitate seed germination under unpredictable climatic conditions, but this remains to be tested.

This multi-year observation of facultative vivipary in four Hedychium taxa suggests that facultative vivipary may be a more common reproductive strategy than that which is known so far. The immediate germination of seeds on the parent plant in at least four taxa also implies that recalcitrance of seeds (i.e. absence of dormancy) may be common in Hedychium (also true for other gingers, Leong-Škorničková, pers. com.). Recalcitrance has been suggested to be a common characteristic of plants growing in wet habitats (Farnsworth 2000), which is true for most Hedychium. Further, morphologically, it has been shown that Hedychium and other gingers have a thin seed coat (Benedict et al. 2015), which may also facilitate recalcitrance. Thus, it is predicted that facultative vivipary may be more common in Hedychium because of the physiology of the seed, i.e. its recalcitrant nature.

The authors’ efforts to summarise vivipary sensu lato across Zingiberaceae from published literature showed that vivipary sensu stricto is absent and that all reported cases of vivipary in other gingers can also only be identified as “facultative vivipary” or pseudovivipary, as in the case of Hedychium. Other genera that display facultative vivipary (except in A. mutica) also show similar characters as observed in Hedychium that favour this reproductive strategy, such as persistent bracts, bract structure that may retain the seeds, and recalcitrant seeds. It was found that both facultative vivipary and pseudovivipary are common amongst gingers with pseudovivipary being more frequent only in Globba (Table 1). Finally, in the genus Hedychium, pseudovivipary is only reported in H. greenii (Fig. 5).

Figure 5. 

Pseudovivipary (Bulbil formation). A Hedychium greenii (the inset in the upper right is an inflorescence) B Alpinia purpurata C Globba multiflora D Larsenianthus careyanus. Photographed by A. Ashokan & Preeti (A).

To understand if vivipary sensu lato is a convergent character in Hedychium, different types of vivipary were mapped on a preliminary molecular phylogenetic tree (modified from nrDNA ITS tree of Wood et al. 2000, with the addition of H. marginatum and H. speciosum var. gardnerianum). It was found that both facultative vivipary and pseudovivipary are currently restricted only to a few members within the Clade IV (as defined in Wood et al. 2000). To understand the relevance of facultative vivipary and pseudovivipary as important reproductive strategies in gingers, it is suggested that future studies should treat different types of vivipary as an important morphological character along with seed characteristics (i.e. presence or absence of dormancy).

Acknowledgements

The authors thank the Ministry of Human Resources and Development (MHRD), the National Geographic Society for research funds to V. Gowda, IISER-Bhopal for the infrastructure, the Council for Scientific and Industrial Research (CSIR) for the senior research fellowship to A. Ashokan and the Heliconia Society International (HSI) for the field research grant to A. Ashokan. We also thank State Forest Departments of Arunachal Pradesh, Manipur, Meghalaya, Mizoram and Nagaland for research permits, Dr. Mark Newman (Royal Botanic Garden Edinburgh) for drawing our attention to the taxonomic error in the identity of H. elatum that appeared in the previous report and Dr. Jana Leong-Škorničková (Singapore Botanic Gardens) and Dr. Neeta Sarangthem for research inputs. We also appreciate the suggestions and advice from two reviewers and the subject editor Dr. Yasen Mutafchiev that has helped us improve the manuscript.

References

  • Aishwarya K, Sabu M (2015) Boesenbergia pulcherrima and B. tiliifolia (Zingiberaceae) in India: notes on the identity, variability and typification. Rheedea 25(1): 59–68.
  • Aswani K, Sabu M (2015) Reproductive biology of Alpinia mutica Roxb. (Zingiberaceae) with special reference to flexistyly pollination mechanism. The International Journal of Plant Reproductive Biology 7(1): 48–58.
  • Baker JG (1894) Scitamineae. In: Hooker JD (Ed.) Flora of British India. L. Reeve & Co., London, 6, 198–264.
  • Benedict JC, Smith SY, Collinson ME, Leong-Škorničková J, Specht CD, Marone F, Xiao X, Parkinson DY (2015) Seed morphology and anatomy and its utility in recognizing subfamilies and tribes of Zingiberaceae. American Journal of Botany 102(11): 1814–1841. https://doi.org/10.3732/ajb.1500300
  • Clarke CB (1890) Plants of Kohima and Moneypore. Journal of Linnean Society (Botany) 25: 75.
  • Cota-Sánchez JH (2004) Vivipary in the Cactaceae: its taxonomic occurrence and biological significance. Flora-Morphology, Distribution, Functional Ecology of Plants 199(6): 481–490. https://doi.org/10.1078/0367-2530-00175
  • Cota-Sánchez JH, Abreu DD (2007) Vivipary and offspring survival in the epiphytic cactus Epiphyllum phyllanthus (Cactaceae). Journal of Experimental Botany 58(14): 3865–3873. https://doi.org/10.1093/jxb/erm232
  • Cox PA, Humphries CJ (1993) Hydrophilous pollination and breeding system evolution in seagrasses: a phylogenetic approach to the evolutionary ecology of the Cymodoceaceae. Botanical Journal of the Linnean Society 113: 217–226. https://doi.org/10.1111/j.1095-8339.1993.tb00338.x
  • Djeddour DH, Pratt C, Shaw RH (2012) The potential for the biological control of Hedychium gardnerianum. A report of the 4th Phase Research on the Biological Control of Hedychium gardnerianum. Produced for Landcare Research, New Zealand and The Nature Conservancy, Hawai’i, 16–17.
  • Edwards S (1823) The Botanical Register 9: 774.
  • Goebel KE (1905) Organography of Plants. Hafner, New York.
  • Holttum RE (1950) The Zingiberaceae of the Malay Peninsula. Gardens’ Bulletin Singapore 13: 1–249.
  • Horaninow PF (1862) Prodromus Monographiae Scitaminarum. St. Petersburg.
  • Kirchoff BK (1997) Inflorescence and flower development in the Hedychieae (Zingiberaceae): Hedychium. Canadian Journal of Botany 75(4): 581–594. https://doi.org/10.1139/b97-065
  • Koenig JG (1783) Descriptions Monandrarum pro annis. In: Retzius AJ (Ed.) Observationes Botanicae. Lipsiae, 3, 45–76.
  • Kress WJ, Prince LM, Williams KJ (2002) The phylogeny and a new classification of the gingers (Zingiberaceae): evidence from molecular data. American Journal of Botany 9(10): 1682–1696. https://doi.org/10.3732/ajb.89.10.1682
  • Larsen K, Lock JM, Maas H, Maas PJ (1998) Zingiberaceae. In: Kubitzki K (Ed.) The Families and Genera of Vascular Plants IV. Flowering Plants: Monocotyledons. Alismatanae and Commelinanae (except Gramineae). Springer, Berlin, Heidelberg, 474–495. https://doi.org/10.1007/978-3-662-03531-3_49
  • Leong-Škorničková J (2007) Taxonomic Studies in Indian Curcuma L. PhD Thesis, Charles University, Prague.
  • Leong-Škorničková J, Thame A, Chew PT (2014) Notes on Singapore native Zingiberales I: A new species of Zingiber and notes on the identities of two further Zingiber taxa. Gardens’ Bulletin Singapore 66: 153–167.
  • Liu Z, Chen J, Bai Z (2004) Comparative studies on reproductive mechanisms of three species in Globba (Zingiberaceae). Wuhan Botanical Research 22(2): 145–152.
  • Loddiges CL (1831) No. 1785. Hedychium urophyllum. The Botanical Cabinet: consisting of coloured delineations of plants, from all countries, with a short account of each, directions for management.
  • Mibang T, Das AK (2017) Taxonomic Investigation on Genus Larsenianthus (Zingiberaceae) of Siang Valley, Arunachal Pradesh. Bulletin of Arunachal Forest Research 32(1–2): 41–48.
  • Mood JD, Tanaka N, Aung MM, Murata J (2016) The genus Boesenbergia (Zingiberaceae) in Myanmar with two new records. Gardens’ Bulletin Singapore 68(2): 299–318. https://doi.org/10.3850/S2382581216000235
  • Newman M, Lhuillier-Chaigneau A, Poulsen AD (2004) Checklist of the Zingiberaceae of Malesia. Blumea Suppl. 16: 1–166.
  • Ofir M, Kigel J (2014) Temporal and intraclonal variation of flowering and pseudovivipary in Poa bulbosa. Annals of Botany 113(7): 1249–1256. https://doi.org/10.1093/aob/mcu037
  • Orchard AE (1973) Zingiberaceae in New Zealand. Records of the Auckland Institute and Museum 10: 109–117.
  • Picheansoonthon C, Tiyaworanant S (2010) A New Species of Globba (Zingiberaceae) from Southern Thailand. Journal of Japanese Botany 85(1): 25–29.
  • Ridley HN (1899) The Scitamineae of the Malay Peninsula. Journal of the Straits Branch of the Royal Asiatic Society 32: 85–184.
  • Roscoe W (1828) Monandrian Plants of the Order Scitamineae. Liverpool.
  • Sanoj E (2011) Taxonomic Revision of the Genus Hedychium J. Koenig (Zingiberaceae) in India. PhD Thesis, University of Calicut, Kerala.
  • Sanoj E, Sabu M, Pradeep AK (2013) Circumscription and lectotypification of Hedychium villosum and its variety H. villosum var. tenuiflorum (Zingiberaceae). PhytoKeys 25: 75–85. https://doi.org/10.3897/phytokeys.25.4113
  • Sarangthem N, Talukdar NC, Thongam B (2013) Collection and evaluation of Hedychium species of Manipur, Northeast India. Genetic resources and crop evolution 60(1): 13–21. https://doi.org/10.1007/s10722-012-9810-1
  • Schumann K (1904) Zingiberaceae, IV, 46. In: Engler A (Ed.) Das Pflanzenreich, Heft 20. Leipzig, Berlin, 1–458.
  • Smith JE (1811) Hedychium. In: Rees A (Ed.) Cyclopaedia. Vol .17. London.
  • Smith WW (1911) Some additions to the Flora of Eastern Himalaya. Records of the Botanical Survey of India 4: 261–272.
  • Srivastava SC (1984) A Taxonomic Study of Genus Hedychium Koen. (Zingiberaceae) in India and its Vicinity. PhD Thesis, University of Calcutta, West Bengal.
  • Wallich N (1853) Initiatory attempt to define the species of Hedychium, and settle their synonymy. Hooker’s Journal of Botany and Kew Garden Miscellany 5: 367–377.
  • WCSP (2018) World Checklist of Selected Plant Families. Facilitated by the Royal Botanic Gardens, Kew. Published on the Internet. http://wcsp.science.kew.org/ [Retrieved 18 February 2018]
  • Williams KJ, Kress WJ, Manos PS (2004) The phylogeny, evolution, and classification of the genus Globba and tribe Globbeae (Zingiberaceae): Appendages do matter. American Journal of Botany 91: 100–114. https://doi.org/10.3732/ajb.91.1.100
  • Wood TH, Whitten WM, Williams NH (2000) Phylogeny of Hedychium and related genera (Zingiberaceae) based on ITS sequence data. Edinburgh Journal of Botany 57(2): 261–270. https://doi.org/10.1017/S0960428600000196
  • Zhou H, Chen J, Chen F (2007) Ant-mediated seed dispersal contributes to the local spatial pattern and genetic structure of Globba lancangensis (Zingiberaceae). Journal of Heredity 98(4): 317–324. https://doi.org/10.1093/jhered/esm032