In this article we will discuss about:- 1. Characters of Commelinaceae 2. Distribution of Commelinaceae 3. Economic Importance 4. Affinities 5. Important Type.
Characters of Commelinaceae:
Herb with jointed stem; leaves sheathing and alternate; in florescence cincinnus; flower, hermaphrodite, actinomorphic; perianth leaves 6 in two whorls; stamens 3+3 or 3; some reduced to staminodes; carpels 3, superior, axile placentation.
A. Vegetative characters:
Herb annual or perennial, erect or creeping rarely climber.
Rhizome, branched jointed with swollen nodes.
Simple, alternate with sheathing base and narrow grass-like blades, entire margin, linear, oval or lanceolate parallel venation.
B. Floral characters:
Axillary, cincinnus, sometimes a monochasial cyme which arises either in the axil of a foliage leaf, e.g., Tradescantia or of a spathe-like bract.
Actinomorphic (Zebrina, Pollia) zygomorphic (Commelina etc.) hermaphrodite, hypogynous, cleistogamous (Commelina), pedicellate, complete, trimerous usually subtended by foliaceous bract or spathe.
Tepals six, in two whorls of three each, the outer whorl green and the inner usually blue, violet, yellow or white, free, imbricate.
Stamen 6, in two whorls, all functional (Tradescantia and Pollia) or more commonly some of them are absent or represented by staminodes, filaments often hairy or beared, bithecous.
Tricarpellary, syncarpous; ovary superior trilocular or sometimes bilocular, axile placentation; ovules one to many in each loculus; style terminal; stigma capitate.
A loculicidal or indehiscent capsule.
Entomophilous. Some are cleistogamous, so self-pollinated.
Distribution of Commelinaceae:
Commelinaceae includes about 50 genera and 700 species. In India it is represented by 11 genera and 75 species.
Economic Importance of Commelinaceae:
Leaves of Commelina are edible and fried with gram flour as Pakoras. The rhizomes of Commelina benghalensis are used as vegetable.
The roots of Commelina obliqua are used as antidote to snake poison. The stem juice of Floscopa scandens is put in sore eyes. Many species of Murdannia, Aneilema and Commelina are used in leprosy.
The roots of Cyanotis and Tradescantia are used for expelling worms in cattle as also for fever.
Rhoeo discolor is used as potherb. Tradescantia, Cyanotis, Zebrina pendula (Wandering Jew) are ornamental.
Affinities of Commelinaceae:
According to Bentham and Hooker, the Commelinaceae appeared under the series Coronarieae. Engler, Rendle and Lawrence included it in the Farinosae just after the Spathiflorae. Core placed it in the Farinales, lying between the Arales and Liliales. Hutchinson treated it, together with the Cartonemataceae, Flagellariaceae and Mayaceae, as constituting the Commelinales and connecting the Najadales and Xyridales.
The Commelinaceae is allied to the Pontederiaceae, the points of resemblance being the ligular ochrea-like sheath and mealy endosperm. Furthermore, the floral structure of Spironema, a member of the Commelinaceae, bears similarity with that of Pontederia of the Pontederiaceae.
As regards the trimerous flowers and nuclear endosperm, the Commelinaceae is related to the Liliaceae. The semi-aquatic habit and amoeboid tapetum of anthers of the Commelinaceae suggest relationship with the members of the Helobiales.
Hutchinson expressed the idea that the Commelinaceae could be derived from both the Alismatales and Butomales.
Common plants of the family:
1. Commelina bengalensis – Vern. Kankaon – produces underground cleistogamous white flowers; weed of ditches and moist places.
2. Cyanotis axillaris – Semi-aquatic herb.
3. Tradescantia – Spiderwort, a favourable object for showing protoplasmic circulation.
4. Rhoeo – a favourite pot plant.
Division of family and chief genera:
The Commelinaceae is divided into two sub-families and each with two tribes:
Sub-family I. Commelinoideae:
Guard cells mostly 4. Flowers zygomorphic.
Tribe (i) Declinateae:
Flower buds bent downwards and away from the inflorescence axis.
Commelina, Floscopa etc.
Tribe (ii) Inclinateae:
Flower buds bent upwards and towards the inflorescence axis.
Cochliostema, Geogenanthus etc.
Sub-family II. Tradescantoideae:
Guard cells mostly 2. Flowers actinomorphic.
Tribe (i) Hexandreae:
All 6 stamens fertile.
Pollia, Zebrina, etc.
Tribe (ii) Triandreae:
Only 3 stamens fertile, the rest being sterile or absent.
Murdannia, Palisota etc.
Important Type of Commelinaceae:
Commelina benghalensis (Fig. 109.1):
Annual weed with semi-erect or creeping.
Erect, aerial, with nodes and internodes.
Simple, exstipulate, sessile with sheathing leaf base, ovate to oblong-lanceolate, multicostate parallel venation and greenish with purplish tinge.
Cymes surrounded by 1-3 spathes or bracts.
Bracteate, pedicellate, bisexual, zygomorphic hypogynous, trimerous, blue coloured; some flowers subterranean and cleistogamous.
Biseriate; outer whorl of 3 tepals represents calyx, polysepalous, valvate or imbricate; inner whorl of 3 represents corolla, polypetalous, 1 petal larger, imbricate.
6 stamens of which 3 are fertile and 3 are sterile staminodes; antiphyllous, light blue filaments, anthers dithecous, discrete and divaricate.
Tricarpellary, syncarpous, trilocular, superior, axile placentation, style terminal, stigma capitate, 1 locule with one ovule and 2 with 2 ovules each.