cells, or a single cell to form whole plants by culturing them on a nutrient medium in a
sterile environment. Elite varieties can be clonally propagated, endangered plants can be
conserved, virus-free plants can be produced by meristem culture, germplasm can be con-
served, secondary metabolites can be produced by cell culture. Besides this, tissue culture
serves as an indispensable tool for transgenic plant production. For nearly any transform-
ation system, an efficient regeneration protocol is imperative. This can be attributed tototi-
potencyof plant cells and manipulation of the growth medium and hormones. Plant cells are
unique in the sense that every cell has the potency to form whole new plantlike stem cells
(stem cell production in mammals is located in time and space, and most mammalian cells
cannot be converted to stem cells). However, having an understanding of each plant species
andexplant(donor tissue that is placed in culture) is essential to the development of an
efficient regeneration system. The physiological stage of the explant plays a very important
role in its response to tissue culture. For example, young explants generally respond better
than do older ones.
This chapter examines the history and uses of plant tissue culture and shows how it is
integral to plant biotechnology, and presents the basic principles of media and hormones
used in plant tissue culture, various culture types, and regeneration systems. Some
people consider tissue culture as more of an art than science since the researcher must
develop an eye for differentiating between good and bad (useful and nonuseful) cultures,
which has often proved to be the difference between success and failure in plant
biotechnology.
5.2 History
The history of plant tissue culture dates back at least to 1902, when Gottlieb Haberlandt, a
German botanist, proposed that single plant cells could be cultured in vitro. He tried to
culture leaf mesophyll cells, but did not have much success. Roger J. Gautheret, a
French scientist, had encouraging results with culturing cambial tissues of carrot in
- The first plant growth hormone indoleacetic acid (IAA) was discovered in the
mid-1930s by F. Kogl and his coworkers. In 1934 Professor Philip White successfully cul-
tured tomato roots. In 1939 Gautheret successfully cultured carrot tissue. Both Gautheret
and White were able to maintain the cultures for about 6 years by subculturing them on
fresh media. These experiments demonstrated that cultures could be not only be initiated
but also maintained over a long period of time. Later in 1955 Carlos Miller and Folke
Skoog published their discovery of the hormone kinetin, a cytokinin. Recall from the pre-
vious chapter that cytokinin is an important class of plant growth regulators. In 1962,
Toshio Murashige and Skoog published the composition a plant tissue culture medium
known asMS(named for the first letters of their last names)medium, which now is the
most widely used medium for tissue culture. Murashige was a doctoral student in
Professor Skoog’s lab, and they developed the now-famous MS medium working with
tobacco tissue cultures. The formulation of MS medium took place while they were
trying to discover new hormones from tobacco leaf extracts, which, when added to tissue
cultures, enabled better growth. In a sense, their experiments could be deemed failures
since they did not discover a new hormone. Nonetheless, they came up with a seemingly
ideal medium for most plant tissue culture work that is used in practically every plant bio-
technology laboratory around the world. This major breakthrough in the field of plant tissue
culture has enabled nearly all the other breakthroughs cataloged in this book. MS medium
114 TISSUE CULTURE: THE MANIPULATION OF PLANT DEVELOPMENT