SYNOPSIS
1.5 Genome size
2.1.1 Zingiberoideae
Subfamily Zingiberoideae contains the members of the previously placed tribes Zingibereae, Hedychieae and Globbeae. The striking floral features of this subfamily are the well-developed lateral staminodes that are generally absent in the Alpinioideae (Fig 2.4 A).
Fig 2.2 Classification of Zingiberaceae (Holtum’s 1950). Number of species has been mentioned in parenthesis.
Fig 2.3 Classification of Zingiberaceae based on molecular data (Kress et al 2002).
The most prominent vegetative feature that is universal in this subfamily is the parallel orientation of the plane of distichy of the leafy shoots with respect to the rhizome (perpendicular orientation in all other Zingiberaceae) (Fig 2.4 B). A second vegetative trait that characterizes the Zingiberoideae is the capacity for members of this subfamily to go into dormancy during the dry season (Fig 2.4 C). Members of Alpinioideae cannot be forced into dormancy, possess tough fibrous rather than fleshy rhizomes, and are always evergreen in their natural habitats. Zingiberoideae has been classified in to two groups based on molecular marker data (Kress et al 2002).
Zingibereae contains several genera. The Curcuma clade consist of Curcuma, Stahlianthus, Hitchenia, and Smithatris, which share cone-like inflorescences of few- flowered, congested bracts. Kaempferia clade consists of Haniffia, Zingiber, Kaempferia, Distichochlamys, Scaphochlamys, Boesenbergia, Curcumorpha and Cornukaempferia. These taxa lack the distinctive pseudostem (except for Zingiber and Haniffia) found in other members of the subfamily. The taxonomy of Hedychium is still unresolved. The four genera in the traditionally recognized Globbeae are united by several morphological characters such as the unilocular ovary with parietal placentation (convergent with Tamijia) and the long-arching filament to which the labellum and/or lateral staminodes are fused (in Globba and Mantisia only).
2.1.1.1 Genus: Curcuma
The genus Curcuma with about 50 species has been circumscribed by its `pouched´
inflorescence bracts and versatile, usually spurred anthers (Fig 2.5). It is a diverse polyploidy complex containing many taxa of economic, medicinal, ornamental and cultural importance, the type species of the genus, C. longa L. (turmeric) being the best-known example (Skornickova et al 2012).
Rhizomes of Curcuma are branched, fleshy and aromatic. Roots often bear conical or ellipsoidal tubers. Leaves are basal and blade is broadly lanceolate or oblong or rarely linear and narrow. The genus can be easily recognized by its large compound spike inflorescence bearing prominent spiral bracts which laterally fuse to form pouches. Each pouch subtends to a cincinnus of two to ten flowers that contain a single versatile anther.
Fig. 2.4 Taxonomic features of Zingiberoideae. A. well-developed lateral staminodes B. parallel plane of distichy of leaves to rhizome (Zingiberoideae), and C. seasonal dormancy
The terminal bracts form a sterile cluster called ‘coma’ very long and often brightly colored. It has two distinct flowering times. Early flowering (April-May) species develop laterally from the rhizome before development of leafy shoot. Late flowering (August-September) species usually develop terminally from the leafy shoots (Sirirugsa 1999).
The plants vary from 50-200 cm in height. Curcuma species are mostly triploid and do not produce seeds. They reproduce asexually by rhizomes. The identification of the members of this genus has traditionally been achieved using morphological data. However, Curcuma species exhibit large morphological variations both inter and intra species, but in some cases, especially early flowering group shows a very similar pattern of morphology between them which leads to confusion in their identification (Apavatjrut et al 1999).
2.1.1.2 Genus: Kaempferia
Kaempferia comprising of more than 60 species, has distribution in tropics and subtropics of Asia and Africa. It contains many aromatic rhizomatous herbal species, which are the ingredients of many ayurvedic drug preparations, and the aromatic essential oil from the rhizome is valuable to perfumery. The vegetative characters of taxa found in Southeast Asia are often associated with the fleshy rhizomes, usually short, with several roots in a bundle. The roots of some species, particularly those with inflorescence separated from and preceding leaf shoots, are fibrous with terminal globular to fusiform storage tubers. Leaves range from one to a few; they are filiform to very broad, rising from the rhizomes, usually with keeled sheathes, short to long petioles, small, inconspicuous, or without ligules (Fig 2.6).
The inflorescence of all species found in Thailand is either separated (in all taxa preceding the appearance of the leaf-shoots), or terminal and beginning with the leaf-shoots. The terminal inflorescence often forms a pedunculate head, and all its primary bracts are always fertile. However, the radical inflorescence is either sessile or very shortly pedunculated, with 2-4 sterile sheathing bracts. The non-tubular primary bract is always accompanied by a shortly bilobed or bilobed-to-the-base bracteole, and subtends only one flower. A combination of the overall floral
morphology is characteristic of the Asiatic Kaempferia species. The labellum is separated from the lateral staminodes almost to the base, and is often deeply bilobed, except that of K. parviflora Wall. ex Baker. The lateral staminodes are always petaloid and the anther crest is always conspicuous and could be entire or dentate, straight or reflexed, and narrow or orbicular. Moreover, the stigma is always cup- shaped with ciliated rims and the stylodial glands are paired and needle-like.
However, morphological features can be greatly variable, even within the same taxon.
Therefore, until the range of character variation of these generic features is fully understood, a single diagnostic character cannot be used for taxonomic decision- making (Picheansoonthon & Koonterm 2008).
2.1.1.3 Genus: Hedychium
Hedychium J. König is an economically important genus, consisting of 65 species worldwide of which NE India has the highest species concentration (24 out of 65 Wood et al 2000; Hamidou et al 2008). Hedychium species are widely cultivated for their perfume, and as a useful raw material for manufacturing paper. Moreover, some species are cultivated for their edible flowers (He 2000). The genus is also of horticultural importance. The inflorescence of H. coronarium, the national flower of Cuba, is aromatic and showy, resembling a cluster of flying white butterflies.
Flowering in Hedychium mainly occurs in summer and autumn, while a few species bloom in winter and spring. The taxonomy of the Hedychium genus is unclear.
Inter-specific hybrids of Hedychium are readily created and natural hybridisation undoubtedly contributes to taxonomic confusion (Wood et al. 2000).
The taxonomy of the ‘white’ and ‘yellow’ gingers (H. flavescens and H. coronarium) is particularly confusing (Fig 2.7). For example, in New Zealand, material described as either ‘white ginger’ or ‘yellow ginger’ has been referred to as H. flavum, H.
flavescens, H. coronarium or H. oblongum in various publications over the past 30 or more years.
Fig 2.5 A representative Curcuma plant. A. Entire plant; B. Inflorescence;
C. Rhizomes.
Fig 2.6 A representative Kaempferia plant. A. Entire plant; B. Inflorescence; C. Rhizomes
Fig 2.7 A representative Hedychium plant. A. Entire plant; B. Inflorescence; C.
Rhizomes.