In bamboo, as in other grasses, the internodal regions of the stem are usually hollow and the vascular bundles in the cross-section are scattered throughout the walls of the stalk instead of in a cylindrical cambium layer between the bark (phloem) and the wood (xylem) as in dicots and conifers. The dicotyledonous woody xylem is also absent. The absence of secondary growth wood causes the stems of monocots, including the palms and large bamboos, to be columnar rather than tapering.[12]
Bamboos include some of the fastest-growing plants in the world,[13] due to a unique rhizome-dependent system. Certain species of bamboo can grow 91 centimeters (36 inches) within a 24-hour period, at a rate of almost 40 millimeters (1+1⁄2 in) an hour (equivalent to 1 mm (0.04 in) every 90 seconds).[14] Growth up to 120 centimeters (47.2 in) in 24 hours has been observed in the instance of Japanese giant timber bamboo (Phyllostachys bambusoides).[15] This rapid growth and tolerance for marginal land, make bamboo a good candidate for afforestation, carbon sequestration and climate change mitigation.[16][17][18]
Bamboo is versatile and has notable economic and cultural significance in South Asia, Southeast Asia, and East Asia, being used for building materials, as a food source, and as a raw product, and depicted often in arts, such as in bamboo paintings and bambooworking. Bamboo, like wood, is a natural composite material with a high strength-to-weight ratio useful for structures.[19] Bamboo's strength-to-weight ratio is similar to timber, and its strength is generally similar to a strong softwood or hardwood timber.[20][21] Some bamboo species have displayed remarkable strength under test conditions. Bambusa tulda of Bangladesh and adjoining India has tested as high as 60,000 psi (400 MPa) in tensile strength.[22] Other bamboo species make extraordinarily hard material. Bambusa tabacaria of China contains so much silica that it will make sparks when struck by an ax
Bamboos have long been considered the most basal grass genera, mostly because of the presence of bracteate, indeterminate inflorescences, "pseudospikelets", and flowers with three lodicules, six stamens, and three stigmata.[25] Following more recent molecular phylogenetic research, many tribes and genera of grasses formerly included in the Bambusoideae are now classified in other subfamilies, e.g. the Anomochlooideae, the Puelioideae, and the Ehrhartoideae. The subfamily in its current sense belongs to the BOP clade of grasses, where it is sister to the Pooideae (bluegrasses and relatives).[24]
The bamboos comprise three clades classified as tribes, and these strongly correspond with geographic divisions representing the New World herbaceous species (Olyreae), tropical woody bamboos (Bambuseae), and temperate woody bamboos (Arundinarieae).[26][5] The woody bamboos do not form a monophyletic group; instead, the tropical woody and herbaceous bamboos are sister to the temperate woody bamboos.[1][24] Altogether, more than 1,400 species are placed in 115 genera.
Most bamboo species are native to warm and moist tropical and to warm temperate climates.[27] Their range also extends to cool mountainous regions and highland cloud forests.[citation needed]
In the Asia-Pacific region, they occur across East Asia, from north to 50 °N latitude in Sakhalin,[28] to south to northern Australia, and west to India and the Himalayas. China, Japan, Korea, India and Australia, all have several endemic populations.[29] They also occur in small numbers in sub-Saharan Africa, confined to tropical areas, from southern Senegal in the north to southern Mozambique and Madagascar in the south.[30] In the Americas, bamboo has a native range from 47 °S in southern Argentina and the beech forests of central Chile, through the South American tropical rainforests, to the Andes in Ecuador near 4,300 m (14,000 ft), with a noticeable gap through the Atacama Desert.[citation needed]
Three species of bamboo, all in the genus Arundinaria, are also native through Central America and Mexico, northward into the Southeastern United States.[31] Bamboo thickets called canebrakes once formed a dominant ecosystem in some parts of the Southeastern United States, but they are now considered critically endangered ecosystems.[32][33][34] Canada and continental Europe are not known to have any native species of bamboo.[35] Many species are also cultivated as garden plants outside of this range, including in Europe and areas of North America where no native wild bamboo exists.
Recently, some attempts have been made to grow bamboo on a commercial basis in the Great Lakes region of east-central Africa, especially in Rwanda.[36] In the United States, several companies are growing, harvesting, and distributing species such as Phyllostachys nigra (Henon) and Phyllostachys edulis (Moso).
