Study of Family Urticaceae

Systematic position/ Classifications:

Venation reticulate, 2 cotyledons                                        Class- Dicotyledons

Flowers incomplete, mostly unisexual, small,

green, Perianth 1-seriate, only one whorl present           Subclass- Monochlamydeae

Flowers unisexual, Perianth lobes sepaloid absent,

gynoecium with free styles, seeds endospermic               Order- Unisexuales

                                                                                                Family- Urticaceae   

Distribution: Members of this family are distributed mainly in tropical regions of the world with 480 species and 41 genera.

Salient features:

Plants are generally fibrous herbs, with stinging hairs (Urtica, Girardinia), latex is absent.

Leaves are simple, alternate or opposite, margin entire or serrate, stipules present. Dried leaves with cystoliths.

Flowers are in cymes or heads, monoecious or dioecious, unisexual, Actinomorphic & hypogynous. Pistilate flowers occurs in male flowers and staminodes are present in female flowers.

Perianth green, sepaloid and consists of 4 perianth leaves arranged in whorls of two each, it united in female flowers.

Male flowers- androecium consists of 4 stamens (rarely 3-5), isomerous, filaments inflexed in bud, anthers explode suddenly when ripe after jerk. Some time a rudimentary pistil is also present. In Pilea muscosa pollen grain discharge profusely when plant shakes therefore called as ‘artillary’ or ‘gunpowder plant’.

Female flowers- gynoecium with single carpel, ovary superior, unilocular with single ovule, style is simple ending in a stigma which is with brush like tuft, scale like staminodes are present at the base of pistil. Ovules erect and is of orthotropous type.

Fruits- is an achene or a drupe enclosed by a persistent Perianth. Seeds are endospermic with oily endosperm and straight embryo.

Note-

Floral formula:

Floral diagram:

Morphological peculiarities:

Predominantly herbaceous plants.

Leaves stipulate with cystolyths.

Presence of stinging hairs.

Flowers unisexual, monochlamydous.

Stamens inflexed in buds and inwardly bent when mature.

Stigma brush like.

Placentation basal.

Economic importance & their uses-

Girardinia heterophylla- stem yields a strong silk like fibre which is mainly used in making twine, ropes, some time course cloth, etc.

Boehmeria nivea- It is largely cultivated in China for the bat fibre which is longer, stronger and most silky of all the vegetable fibres.

Mautia, Urtica dioica yields very useful fibre.

Garden Plants- Pilea, Pellionia are grown in pots in garden due to foliage and beautiful flowers.

Edible plants- Trema orientalis fruits are useful for eating purpose.

The wood of Trema is useful in making charcoal for gunpowder.

Present status, affinities, phylogeny & inter-relationship of Urticaceae:

Based on floral and wood anatomy families like Ulmaceae, Moraceae, Urticaceae are treated under one family Urticaceae by Bantham & Hooker’s.

Moraceae and Urticaceae both have unisexual flowers, stamens as many as perianth lobes  and ovary is unilocular.

Engler and Prantl and Hutchinson considered Urticaceae as most advanced family amongst Moraceae and Urticaceae under order Urticaless.