ZINGIBERALES

order of flowering plants belonging to the class called monocotyledon (characterized generally by the presence of a single seed leaf). Zingiberales comprises 89 genera and 1,800 species in eight families. Among its best-known members are bananas, gingers, and cannas. Like other monocots, members of this order lack a cambium. Even though plants in this group are very diverse in gross aspect, one nearly universal feature exists: cross sections of leaf stalks of most members display vascular bundles (conducting strands) in prominent arcs, interspersed with air canals. Plants assigned to the Zingiberales range in size from herbs a few centimetres in height to the traveler's tree (Ravenala madagascariensis), which grows to a height of 8 m (26 feet), displaying a fan-shaped array of 20 or more leaves which are 4 to 5 m long. Zingiberales are widely distributed in the tropics, but individual families are limited in range. Several genera belonging to the Zingiberales are of major economic importance. Foremost are the hybrids of banana (Musa paradisiaca), which yield the edible banana and plantain fruits. Manila hemp is the name given to the strong fibres of the leaf stalks of Musa textilis, an inedible banana native to the Philippine Islands. These fibres are made into ropes and twine. Arrowroot starch, used in special diets and in fine baking, is extracted from the rhizomes (stocky underground stems) of Maranta arundinacea, cultivated mainly in the West Indies. The rhizomes of Canna are also edible, but many cultivars in this genus are most noted for their showy flowers. Most plants in the large ginger family (Zingiberaceae) have aromatic leaves and flowers. Zingiber officinale yields true ginger; other genera are the source of additional spices, medicinal products, dyes, and condiments. Most Zingiber members are native to tropical Asia, though several species are grown as ornamentals in greenhouses and can survive winters in mild temperate regions. The traveler's tree and related plants develop thin stems surmounted by the current crop of leaves. Encircling scars indicate the position of leaf sheaths already shed by the mature stems. The most common type of stem in this order is short and below ground. In many gingers, all leaves arise at ground level, their clasping sheaths and leaf bases hiding the stem. In the bananas, the vegetative stem is a stocky, subterranean structure that extends above the level of the soil for a short distance; it is surrounded by massive leaves and is never visible. Each new leaf grows inside the sheath of the preceding one. One edge of the leaf overlaps the other resulting in a slight dwarfing of the edge that is lowermost. What appears to be the stem of the banana plant is, in reality, a false trunk consisting of many leaf sheaths that are rolled up longitudinally to form a cylinder. In Zingiberales, branches arise from underground stems and are known as rhizomes (when elongate) or suckers (when short and bulky); they produce leaves and eventually emerge above the surface of the soil. When separated from their parents, such units reproduce the species vegetatively. This method of propagation assures the perpetuation of desirable genetic traits; if grown from seed, some expected qualities may be replaced by others that are not as desirable. When mature enough to flower, plants of some genera (such as the banana), produce flower stalks (inflorescences) at the tip of the vegetative stem; lower portions of this stem are sheathed by leaf bases. A flowering stem may be very long, emerging just below the terminal tuft of current leaf blades. Typically, the inflorescence is an erect axis bearing bracts (bladeless leaves). The ultimate clusters of flowers arise in conjunction with the bracts and usually are much-branched. The typical flower of this order has three petals, three sepals, six stamens (male), and a pistil consisting of three carpels (and differentiated into a basal ovary); many variations occur. In some species of the banana family, flowers are functionally unisexual (male or female), thus ensuring cross-pollination. Even though cultivated bananas produce flowers with a rank odour and much nectar, fruits develop without pollination; seeds do not develop even if flowers are pollinated. Flowers of wild bananas and those of Strelitzia are bird-pollinated. In the ginger family, butterflies are the pollinators. order of monocotyledonous flowering plants, a division of the subclass Zingiberidae. Among well-known members are bananas, gingers, and cannas. Additional reading N.W. Simmonds, The Evolution of the Bananas (1962), an account of the natural subdivisions of the genus Musa, based on cytotaxonomic and genetic studies and on the origin of cultivated bananas; R.H. Stover and N.W. Simmonds, Bananas, 3rd ed. (1987).