Nepenthes

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Nepenthes

Description

Carnivorous, dioecious, woody or subwoody climbers or subshrubs, terrestrial or epiphytic. Leaves exstipulate; Inflorescence terminal, appearing lateral by subsequent growth, a paniculoid thyrse or raceme, of 6-300 flowers, the main axis with indeterminate growth, the partial inflorescences 1-flowered (racemose) or 2-flowered, less usually 3-40-flowered, bracteate or ebracteate. Fruit sometimes stipitate, a loculicidally dehiscent capsule with 4 valves containing 50-500 seeds. Seeds filiform, 3-25 mm long, slender due to long basal and apical appendages.

Distribution

Genus of c. 87 species, mostly in Malesia, but with c. 8 outlying species in: Madagascar (2), Seychelles (1), Sri Lanka (1), NE India (1), Indochina (6-9), Solomon Islands (1), New Caledonia (1) and Australia (1). Most species are found in Borneo and Sumatra. No species are known from the Lesser Sunda Islands east of Java, nor from the northern tip of Sumatra.

Anatomy

— Metcalfe & Chalk (1950) provide a report on the vegetative anatomy based on their examination of two horticultural hybrid taxa, Nepenthes ‘Hainaniana’ and N. ‘Ratcliffeana’ as well as summarising data from previous work. Much of what follows is based on their work.

Leaf blade with distinct palisade in some taxa, indistinct in others. Stomata on lower surface only, ranunculaceous. Hypoderm usually present, especially at the upper surface, of 1-3 cell layers. Mesophyll including up to 5 layers of palisade cells and cells with spiral bands of cellulose thickening. Midrib similar to petiole.

Petiole with vascular cylinder adaxially flattened, of widely spaced collateral bundles supported by fibres and connected by a zone of sclerotic cells. Larger adaxial bundles with xylem uppermost, smaller adaxial bundles inverted. Abaxial bundles variously orientated. One medullary bundle in one taxon, two in another; xylem adaxial. Small bundles present in petiole wings. Tanniniferous deposits and occasional cluster crystals in mesophyll cells.

Tendril with vascular cylinder of collateral bundles embedded in sclerenchyma. Adaxial bundles sometimes inverted, that is, with xylem internal. Medullary bundle(s) well developed or absent.

Pitcher with epidermis of thick-walled cells. Stomata present on outer surface, and both surfaces of the lid. Spirally thickened cells embedded, walls supplied by numerous vascular bundles with very well-developed phloem. Larger bundles sheathed in fibres (Metcalfe & Chalk 1950).
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Cytology

Lowrey (1991) reviewed previous work on the chromosomes of Nepenthes. This had been based on two cultivated species (N. rafflesiana and N. thorelii) and one horticultural hybrid. The family had been considered notable for very high chromosome numbers (n = 39 and 40) and possible aneuploidy. Lowrey discounted previous reports of 2n = 78 (based in part on N. rafflesiana) and possible aneuploidy in Nepenthes and reported 2n = 80 from N. rafflesiana and six other species (unspecified) from Malaysia and Singapore. Thirteen enzyme systems were examined for isozyme number. All enzymes exhibited isozyme numbers within the ranges typical of diploid seed plants. Lowrey interpreted the lack of duplicated loci as lack of evidence for a polyploid origin for the family despite the high chromosome number.

Heubl & Wistuba (1997) confirmed 2n = 80 in their investigation of 15 species: N. albomarginata, N. clipeata, N. distillatoria, N. eymae, N. gracilis, N. khasiana, N. madagascariensis, N. pervillei, N. rafflesiana, N. reinwardtiana, N. stenophylla, N. tentaculata, N. thorelii, N. truncata, and N. veitchii. They reported the chromosomes of all these species to be similar to each other in shape and very small, from 0.5-2 microns in length in metaphasic karyotypes. The chromosomes are metacentric to submetacentric. Centromeres are only visible at mid-metaphase. Chromosome groupings within the karyotype were not detected by Heubl & Wistuba.

This remarkable chromosomal uniformity is consistent with the ease with which fertile interspecific hybrids are produced in the wild and in horticulture. It provides little taxonomic insight into the genus. However, several major species-groupings in the genus have not yet been sampled. Cytological investigation of the Montanae and Insignes groups together with the Malesian ‘paniculate’ species is desirable.

Uses

The main value of Nepenthes in international commerce is in the horticultural trade, where it probably far exceeds 15 million dollars per annum in our estimation (see ‘Conservation’, p. 13).

In SE Asia, the use of N. mirabilis as toy phallocrypts in New Guinea is probably the most obscure. Stems of several species are used for making rope, that of N. ampullaria being considered of particularly good quality, being very durable when used in, for ex-ample, tying fences. Fluid from unopened pitchers is potable (pers. obs.) and used to treat inflammation of the eyes and both indigestion and other stomach problems. Boiled roots of N. ampullaria and N. gracilis have both been used to treat stomachache. Nepenthes reinwardtiana has been used to facilitate healing of skin and as an astringent. Opened pitchers of the larger pitchers are used to cook rice in, imparting an interesting flavour. The last use is reflected in one of the common names of many species in various languages, which translates as ‘monkeys’ rice pots’. Other common names which may reflect uses translate as ‘monkeys’ goblet’ and ‘monkeys’ water-scooper’. A detailed compilation of common names based on those recorded on herbarium specimens is given by Danser (1928) from which most of the above uses have been obtained.

Citation

Jebb & Cheek - in Blumea. 1997: 5