Propagation from preexisting meristems
Micropropagation is the true-to-type propagation of selected genotypes using in vitro culture techniques. Depending on the species and cultural conditions, in vitro propagation can be achieved by: enhanced axillary shoot proliferation; node culture; de novo formation of adventitious shoots through shoot organogenesis; and nonzygotic embryogenesis. This chapter discusses the concepts related to propagation by shoot and node culture. Shoot growth in mature plants is restricted to specialized regions which exhibit little differentiation and in which the cells retain the embryonic capacity for unlimited division. These regions, called apical meristems, are located in the apices of main and lateral buds of the plant. Murashige originally described three basic stages for successful micropropagation. Currently it is now agreed that there are five stages critical to successful micropropagation. They are: Stage Zero: donor plant selection and preparation, Stage One: establishment of aseptic cultures, Stage Two: proliferation of axillary shoots, Stage Three: pretransplant (rooting), and Stage Four: transfer to natural environment.