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In this article we will discuss about:- 1. Characters of Nepenthaceae 2. Functions of Nepenthaceae 3. Distribution 4. Economic Importance.
Characters of Nepenthaceae:
Shrubby plants generally climbing by leaves; dioecious; pendant showy pitchers and the monadelphous staminate flowers.
A. Vegetative characters:
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Habit:
Herbaceous or shrubby plants.
Root:
Tap, tetrach to hexarch.
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Stem:
Rhizone with a ring of collateral open, endarch vascular bundles.
Leaf:
Alternate, simple, petiolate, leaf apex tendrillar, the tendril terminating into a pitcher with apical lid or operculum, stipules absent.
Leaf highly metamophosed into prey catching organ:
The fully developed leaf of Nepenthus has four parts viz.:
(i) The lamina or winged portion directly seated on stem,
(ii) The tendril coming out of lamina being the prolongation of midrib of lamina,
(iii) The pitcher or acidium (the tendril terminates into it) and
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(iv) The operculam or lid at the apex of the pitcher.
The morphology of different parts as explained by different authors is given below:
A.P. de Candolle:
The lid or operculum is the true leaf blade or lamina, the pitcher and rest of the other parts represent the petiole and its parts.
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F.O. Bower:
On the basis of foliar theory supported by H. Macfarlane and others, the lid is formed as a result of fusion of two original leaflets of a pinnate compound leaf, the tendril and the so called winged expansion (blade) represent the petiole.
K. Geobel:
The entire leaf as a result of extreme metamorphosis had under gone a rebuilding of parts, the pitcher representing the true lamina or leaf blade, the tendirl as petiole, the so called winged base or limb as the winged base or hypopodium, the lid or operculum as outgrowth or appendage of the upper surface of the leaf blade or lamina.
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B. Floral characters:
Inflorescence:
Recemose to paniculate.
Flower:
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Actinomorphic, unisexual, greenish, small, hypogynous.
Perianth:
Haplochlamydous, simple 2 dimerous rarely tepals 3 or 5-6, free, imbricate, very rarely connate at the base, arranged crosswise in two whorls (2 + 2). Perianth leaves elliptic, round or linear, hairy outside, glandular inside, the glands are larger in staminate flower than that pistillate flower.
Staminate flower:
Perianth:
As above.
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Androecium:
Stamens 4-24, the filaments with anthers are united together in a column or tube – monadelphous in a columns; anthers distinct bithecous, extrorse, dehiscing longitudinally; pollen grains in tetrad.
Pistillate flower:
Perianth:
As above.
Gynoecium:
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Capels 4 usually, rarely 3, opposite to perianth leaves, superior; 3-4 locular ovary, axile placentation; style very small or absent; stigma persistent, discoid, flat or concave, ovules many, anatropous, bitegmic with dorsal raphe.
Fruit:
Loculicidal capsule, elongated, leathery.
Seed:
Numerous, saw-dusk like, long, narrow, winged with fleshy endospermic.
Pollination:
Entomophilous.
Floral formulae:
Function of Nepenthaceae:
The pitcher functions as digestive as well as insect catching trap, the edge of the pitcher is bent inside, the operculum or lid is apical, the entrance or the hole of the pitcher including the base of the lid is beset with honey or nectarglands, the lid functions as the landing stage as well as an attracting object for the prey.
Insects and flies attracted by honey and bright colour of the lid of the pitcher descend among the glands and presently arrive at the stillpery part near the entrance and fall down in the pitcher and ultimately get drawned in the liquid filling the base of the pitcher. The entrapped prey dies and decays, the plant gets nourishment by absorbing the fluid containing the putrifying body of the prey.
Distribution of Nepenthaceae:
Nepenthaceae is a unigeneric monotypic family comprising only one genus Nepenthus with about 50 species. It is mainly confined to Indo-Malayan region of the globe. Nepenthus khasiana L. is met with in Khasia hills in Assam.
Economic Importance of Nepenthaceae:
1. Ornamentals:
Many species and hybrids of Nepenthes are cultivated domestically in glass houses as novelties.
2. Cordage:
The stems of Nepenthus distillatoria (Sri Lanka) and N. reinwardtiana (Malaysia) are used as a kind of cordage as well as for making baskets.
