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In this article we will discuss about:- 1. Characters of Oxalidaceae 2. Distribution of Oxalidaceae 3. Economic Importance 4. Affinities.
Characters of Oxalidaceae:
Leaves exstipulate, flowers actinomorphic calyx imbricate; contorted corolla; stamens connate at the base; styles free, fruit capsule and seeds with an elastic testa.
A. Vegetative characters:
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Habit:
Mostly perennial herbs, rarely shrubs or trees (Averrboa).
Stem:
Fleshy rhizome or bulbous tubers, almost aerial stemless or very short stemmed, rosettes of radical leaves.
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Leaf:
Alternate, pinnately or palmately compound; exstipulate; often long petioled, leaflets obcordate and characteristically folding at night (nyctinostic movements) sometimes sensitive to touch (Biophytum sensitivum); leaves sometimes replaced by phyllodes (Oxalis buplurifolia). Cauline leaves are arranged in rosettes (Biophytum), sessile in many species of oxalis.
B. Floral characters:
Inflorescence:
Solitary or subumbellate, rarely racemose or cymose.
Flower:
Bracteate, bracteolate, complete, hermaphrodite, actinomorphic, pentamerous, hypogynous; often on long peduncles.
Calyx:
5 sepals, polysepalous or slightly united, imbricate or quincuncial, persistent.
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Corolla:
5 petals, free or slightly united at the base, short-clawed; imbricate or twisted.
Androecium:
Stamens 10, fused at the base (monadelphous), obdiplostemonous, introrse; rarely 5 stamens are without anthers.
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Gynoecium:
Pentacarpellary, syncarpous, ovary superior, pentalocular, one or more anatropous ovules in each locule, axile placentation; styles 5, free and persistent.
Fruit:
Loculicidal capsule, rarely berry.
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Seed:
Endospermic.
Pollination:
Entomophilous.
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Floral formula:
Distribution of Oxalidaceae:
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The family comprises of 8 genera and 900 species, being prevalent in the tropics and subtropics and having richest representation in Southern Hemisphere. From India 2 genera and a dozen species have been reported.
Economic Importance of Oxalidaceae:
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1. Food:
Tuberous roots of O. tuberosa are used as food in India. Leaves of O. acetosella (common wood sorrel) are used as salads and stems of O. pescaprae as a vegetable. The leaves of Oxalis (sour grass) are chewed by the children for their pleasant sour taste due to oxalic acid.
2. Ornamental:
Oxalis articulata, O. deppei, O. bedysaroides, Averrhoea (evergreen tree) and Biophytum sensitivum are grown in gardens.
Affinities of Oxalidaceae:
Bentham & Hooker treated Oxalidaceae only as a tribe Oxalideae under family Geraniaceae. Cronquist (1961) and Thorne (1963) and others treat it as an independent family under order Geraniales. It has close affinities with Geraniaceae.
Common plants of the family:
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1. Biophytum sensitivum – a weed of rice-fields and road-sides with rosette of sensitive pinnate leaves.
2. Oxalis corniculata – a weed with ternate leaves, constituting a leaf-mosaic.
Division of the family and chief genera:
The family is sub-divided into two tribes according to number of stamens and nature of fruit.
Tribe I. Oxalideae:
Stamens 10 in number, in two series. Genera : Oxalis, Biophytum, Averrhoa, Eichleria etc.
Tribe II. Hypseochareae:
Stamens 15 in three rows. Genus : Hypseocharis.
