Oxalis Species: In Vitro Culture, Micropropagation, and the Formation of Anthocyanins

Abstract

The genus Oxalis L. is the largest of the Oxalidaceae (Cronquist 1981; Mabberley 1987), and is represented by some 500 species worldwide. While being cosmopolitan, the main centres of diversity for Oxalis are in South America and South Africa. The South Western Cape of the latter region is particularly rich in Oxalis species; Salter (1944) reported 208 species. These dicotyledonous plants exhibit a wide range of growth habits (herbs, many geophytes with bulbs or tubers, undershrubs) and inflorescence structures (Salter 1944). Their leaves are alternate, usually compound, digitate or pinnate. Most species exhibit nastic movement. In addition to having attractive shapes, most spectacular during rainy months, leaves of some species also have attractive spotting. Flowers are regular, bisexual with a pentamerous perianth. Under bright light conditions, the flowers of Oxalis open in a wide range of hues, varying from white through yellow to scarlet. Bicoloured tubular or bell-shaped flowers occur, mostly with yellow throats (Salter 1944). Many Oxalis species are geophytes and bear a variety of perennating organs, including root tubers, stolons, bulbili and bulbs. Aerial bulbili are also produced by some species. Seeds are small, endospermous and are produced in a fruit (capsule) the dehiscence of which is explosive (Knuth 1930).