8 Tissue Culture and Transformation

Abstract

INTRODUCTION
Plant Tissue Culture
The basic property of totipotency that enables plant cells derived from various differentiated organs like leaves, roots, cotyledons, or hypocotyls to regenerate whole plants allows the development of a variety of tissue culture/regeneration procedures, as well as methods for the efficient generation of genetically transformed plants. Crucial in these processes is the use of certain phytohormone combinations, basically auxins and cytokinins, in synthetic growth media that induce the initial dedifferentiation of cells and the subsequent redifferentiation into organized structures. Typically, explants like leaf disks or stem, root, or hypocotyl segments, or protoplasts isolated from leaves, are first induced to form callus that later, via organogenesis, regenerates into shoot and root structures or may form embryos via somatic embryogenesis. After the formation of the general structure of the plant body, consisting of an organized shoot with a developed root system, the regenerants may be transferred from the axenic culture to soil. The regenerated plants usually complete their normal life cycle with the formation of seeds or other propagative structures like tubers (for comprehensive presentations, see Vasil 1984for comprehensive presentations, see Vasil 1985for comprehensive presentations, see Vasil 1986; Dixon 1985; Lindsey 1991, 1992). The broad spectrum of in vitro culture techniques is reflected in the variety of applications, a few of which we briefly mention here.

A large number of plant species have been introduced into cell suspension culture. Although this technology is expected to allow the industrial production of plant (secondary) metabolites (Constabel and Vasil 1988), it is to date almost exclusively applied on a...