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In this article we will discuss about:- 1. Characters of Iridaceae 2. Distribution of Iridaceae 3. Economic Importance 4. Affinities.
Characters of Iridaceae:
Herb, perennial by corm, rhizome; flower homochlamydeous or heterochlamydeous, trimerous, hermaphrodite, actinomorphic or zygomorphic; perianth-gamphyllous, in 2 whorls, – inner smaller, stamens 3+3 (inner whorl absent or suppressed). Free, epiphylous; gynoecium – tricarpellary, syncarpous, inferior, trilocular, axile placentation, stigmas – 3, frequently divided and petaloid, fruit capsule.
A. Vegetative characters:
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Habit:
Herbs perennial by corm, bulb and rhizome; plants scapose.
Root:
Adventitious.
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Stem:
Corm, rhizome or bulb, solitary or several.
Leaf:
Radical, cauline, often crowded at the base of the stem; parallel veined, simple, exstipulate, sessile; leaf base sheathing; leaves equitant in 2 ranks and isobilateral.
B. Floral characters:
Inflorescence:
Inflorescence usually small cyme variously arranged. In Iris the flowering axis ends in a flower (which opens first), and has small lateral cymes each invested by a spathe.
Flower:
Hermaphrodite, trimerous, regular, actinomorphic (Iris and Crocus) or sometimes zygomorphic (Gladiolus, Freesia), emerging from a spathe of 2 or more bracts, epigynous.
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Perianth:
Six, in two whorls, three outer ones (sepals) often petal-like all the six perianth leaves, usually gamophyllous and form a tube (scarcely perceptible in Iris) adherent to the ovary, superior.
Androecium:
Stamens three, free or united, epiphyllous attached to the outer whorl of perianth lobes, inner whorl of three suppressed, anthers extrorse, superior.
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Gynoecium:
Tricarpellary, syncarpous; ovary inferior trilocular; placentation axile, rarely, unilocular with parietal placentation; style single; stigma three, sometimes expanded and petal-like as in Iris, where they add much to appearance of the flower.
Fruit:
A capsule.
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Seed:
Endosporic, rounded or angular compressed.
Pollination:
Entomophilous.
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Floral formula:
Distribution of Iridaceae:
Iridaceae or Iris family of about 70 genera and 1800 species. It is distributed in both tropical and temperate regions.
Economic Importance of Iridaceae:
1. Food:
Starchy corms and rhizomes after boiling are used as food.
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2. Medicinal:
The rhizome of I. foetidissima is a cure for mental diseases, such as hysteria. Saffron is medicinal (emmenagogue) and used as valuable drug and a colouring substance. Orris root, the dried rhizomes of Iris florentina and I. germanica are used in perfumery and as an aromatic flavourant in dentifrices.
Bulbs and rhizomes are rich in starches, fats, volatile oils and little acrid matter. They have stimulating effects and are used as emollient. Roots of Iris germanica are diuretic and used in gallbladder diseases.
3. Dye:
Dried stigmas of Croccus sativus yield saffron (Kesar) of commerce used as a dye and in confectionary.
4. Ornamental:
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Belamcanda, Crocus, Iris, Ixia are decorative plants.
Affinities of Iridaceae:
Iridaceae resembles Liliaceae in arrangement of floral whorls and general structure of flower but differs in having an inferior ovary and only one whorl of stamens, so it is generally included in the Liliflorae (Liliales).
However, Hutchinson placed the family in an order by itself (Iridales). Takhtajan’s Iridales included not only the Iridaceae but also the Geosiridaceae, Burmanniaceae and Corsiaceae.
The Iridaceae, while resembling the Amaryllidaceae in the inferior ovary and that family and the Liliaceae in the germination of seeds, is distinguished from other families of the Liliales by the presence of a single whorl of stamens. Moreover, the pollen-grains of the Iridaceae and Amaryllidaceae are similar.
Like the arborescent Liliaceae and Amaryllidaceae, secondary growth takes place by cambial activity in some members of the Iridaceae (Aristea, Klattia, Witsenia). The Iridaceae is related to the Haemodoraceae in which the outer whorl of stamens is suppressed instead of the inner whorl.
It has been assumed that the Iridaceae originated from the lilliflorean stock or directly from the Amaryllidaceae by way of reduction in the inner whorl of stamens.
Common plants of the family:
1. Crocus sativus (Saffron, vern Kesar) – extensively cultivated in Kasmir, the orange coloured dried stigmas constitute the saffron of commerce.
2. Iris – Cultivated for gorgeous flowers.
3. Cipura poludosa – a garden plant.
Division of the family of chief genera:
The Iridaceae is divided into three subfamilies:
Sub-family I. Crocoideae:
Leaves linear or filiform in several rows. Spathe 1 – flowered. Flowers regular. Perianth whorls subequal. Examples: Crocus and Romulea.
Sub-family II. Iridoideae:
Leaves equitant, in 2 rows. Spathe 2 to several-flowered. Flowers regular. Perianth whorls unequal. Examples: Belamcanda, Iris, Sisyrinchium, etc.
Sub-family III. Ixioideae:
Leaves equitant, in 2 rows. Spathe 1-flowered. Flowers medianly zygomorphic. Examples: Gladiolus, Ixia, etc.
