Tissue Culture

Abstract Plant tissue culture, or the aseptic culture of cells, tissues, organs, and their components under defined physical and chemical conditions in vitro, is an important tool in both basic and applied studies as well as in com- mercial application. It owes its origin to the ideas of the German scientist, Haberlandt, at the begining of the 20th century. The early studies led to root cultures, embryo cul- tures, and the first true callus/tissue cultures. The period between the 1940s and the 1960s was marked by the devel- opment of new techniques and the improvement of those that were already in use. It was the availability of these tech- niques that led to the application of tissue culture to five broad areas, namely, cell behavior (including cytology, nutrition, metabolism, morphogenesis, embryogenesis, and pathology), plant modification and improvement, pathogen- free plants and germplasm storage, clonal propagation, and product (mainly secondary metabolite) formation, starting in the mid-1960s. The 1990s saw continued expansion in the application of the in vitro technologies to an increasing number of plant species. Cell cultures have remained an important tool in the study of basic areas of plant biology and biochemistry and have assumed major significance in studies in molecular biology and agricultural biotechnology. The historical development of these in vitro technologies and their applications are the focus of this chapter.

This review presents an overview of the culture media and practices used in plant tissue culture and developmental biology. The compositions of the most commonly used basal media, especially Murashige and Skoog (MS) and modified MS (MMS), Gamborg’s B5 medium and B5 modifications, Woody Plant Medium (WPM), and Driver and Kuniyuki Woody plant medium (DKW) are discussed, along with typical basal medium manipulations to elicit and support various developmental responses. The most commonly used plant growth regulators and their applications to promote various developmental responses are examined, along with a presentation of the classical phytohormone developmental models for organogenesis and somatic embryogenesis. Elaborated developmental models for both organogenesis and somatic embryogenesis, with emphasis on discrete developmental steps, occasional need for multiple manipulations in culture to achieve a single developmental step, and identification of responsive tissue types in mixed cultures are explored. It is hoped that the information presented here will lead to a deeper understanding of basic tissue culture responses and will assist the reader in the decision-making process by identifying appro- priate media and culture conditions for a particular species or application, or by providing a suitable starting point, should further customization be required.