Nepenthes rajah is a carnivorous pitcher plant species of the family Nepenthaceae. It is endemic to Mount Kinabalu and neighbouring Mount Tambuyukon in Sabah, Malaysian Borneo. Nepenthes rajah grows exclusively on serpentine substrates, particularly in areas of seeping ground water where the soil is loose and permanently moist. The species has an altitudinal range of 1,500–2,650 m (4,920–8,690 ft) above sea level and is thus considered a highland or sub-alpine plant. Due to its localised distribution, N. rajah is classified as an endangered species by the IUCN and listed on CITES Appendix I. The species was collected by Hugh Low on Mount Kinabalu in 1858, and described the next year by Joseph Dalton Hooker, who named it after James Brooke, the first White Rajah of Sarawak. Since being introduced into cultivation in 1881, it has always been a sought-after species, although costly and hard to cultivate. Tissue culture has allowed it to become more widespread in cultivation. N. rajah is best known for the giant urn-shaped traps it produces, which can grow up to 41 cm (16 in) high and 20 cm (7.9 in) wide. These are capable of holding 3.5 L (0.92 US gal) of water and in excess of 2.5 L (0.66 US gal) of digestive fluid, making them probably the largest in the genus. N. rajah can trap mammals as large as rats. N. rajah occasionally traps small vertebrates such as frogs, lizards, and even birds. Insects, and particularly ants, are its staple prey. The pitchers are host to many other organisms, some so specialised that they cannot survive anywhere else, and are called nepenthebionts. N. rajah has two such mosquito taxa named after it: Culex rajah and Toxorhynchites rajah. The species is able to hybridise in the wild with all other locally occurring Nepenthes species.
Etymology Joseph Dalton Hooker described Nepenthes rajah in 1859, naming it in honour of James Brooke, the first White Rajah of Sarawak. 'Rajah Brooke's Pitcher Plant' is an accurate, but seldom-used common name. N. rajah is sometimes called the 'Giant Malaysian Pitcher Plant' or simply 'Giant Pitcher Plant', although the binomial name remains by far the most popular way of referring to this species. The specific epithet rajah means "King" in Malay and this, coupled with the impressive size of its pitchers, has meant that N. rajah is often called the "King of Nepenthes".
Plant characteristics
Nepenthes rajah is a scrambling vine. The stem usually grows along the ground, but climbs whenever it comes into contact with a suitable support. The stem is up to 30 mm (1.2 in)) thick and may reach up to 6 m (20 ft) in length, although it rarely exceeds 3 m (9.8 ft). The leaves are distinctive and reach a large size. They are leathery in texture with a wavy outer margin. The leaves are characteristically peltate, whereby the tendril joins the lamina on the underside, before the apex. The tendrils are inserted within 5 cm (2.0 in) below the leaf apex and reach a length of approximately 50 cm (20 in).
Pitchers The pitcher is a trap consisting of the main pitcher cup, covered by an operculum or lid. A reflexed ring of hardened tissue, the peristome, surrounds the entrance. N. rajah produces two distinct types of trap. "Lower" or "terrestrial" pitchers, the most common, are very large, richly coloured, and ovoid in shape. Exceptional specimens may be more than 40 cm (16 in) in length and hold 3.5 L (0.92 US gal) of water and over 2.5 L (0.66 US gal) of digestive fluid, although most do not exceed 200 ml (6.8 U.S. fl oz). The lower pitchers rest on the ground. They are usually red to purple on the outside, lime green to purple on the inside. Mature plants may in addition produce much smaller "upper" or "aerial" pitchers, which are funnel-shaped, and usually more colourful. The tendril attachment is normally at the rear of the pitcher cup. True upper pitchers are rare, as the stems rarely attain lengths greater than a few metres before dying off. The peristome has a distinctive scalloped edge and is greatly expanded, forming a red lip around the trap's mouth. A series of raised ribs intersect the peristome, ending in short, sharp teeth that line its inner margin. The inner portion of the peristome accounts for around 80% of its total cross-sectional surface length. The huge, vaulted lid is a distinguishing feature of this species. It is ovate to oblong in shape with a distinct keel down the middle, and two prominent lateral veins. The spur at the back of the lid is approximately 20 mm (0.79 in) long and unbranched. The plant has very large nectar-secreting glands covering its pitchers. The inner surface of the pitcher is wholly glandular, with 300 to 800 glands/cm2 (1,900 to 5,200 glands/in2).
Flowers N. rajah seems to flower at any time of the year. Flowers are produced in large numbers on inflorescences that arise from the apex of the main stem. N. rajah produces a very large inflorescence that can be 80 cm (31 in), and sometimes even 120 cm (47 in) tall. The individual flowers of N. rajah are produced mainly in pairs on reduced partial peduncles and so the inflorescence appears superficially like a raceme, though it is technically a racemose panicle, that is, a panicle with branching so greatly reduced as to appear raceme-like. The flowers are reported to give off a strong sugary smell and are brownish-yellow in colour. Sepals are elliptic to oblong and up to 8 mm (0.31 in) long. Like all Nepenthes species, N. rajah is dioecious, which means that individual plants produce flowers of a single sex. Fruits are orange-brown and 10 to 20 mm (0.39 to 0.79 in) long . A study of 300 pollen samples taken from a herbarium specimen (J.H.Adam 2443, collected at an altitude of 1,930–2,320 m (6,330–7,610 ft)) found the mean pollen diameter to be 34.7 μm (0.00137 in) (SE=0.3; CV=7.0%).
Carnivory
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