Tissue culture is a method of propagation using small bits of plant
tissue. These bits are seperated from the plant and placed under
sterile conditions in an artificial medium like agar. Given the right conditions
the cells will continue to grow and divide. Cells in culture don't grow
old as they are efectivly in suspended animation, so can be kept in this condition indefinately, thus saving
valuable space for the breeder. There are two types of tissue culture:
1. Meristem culture. The meristem is the where the plant is
actively growing, and the cells are dividing. The meristem is usually
free of viruses and other pathogens, so meristem culture is used to
obtain a disease free clone.
2. Callus culture. The plant tissue is induced to form
undifferentiated growth or a callus, then induced to differentiate into
the various organs by finding the proper balance of hormones. In
meristem culture organs are already differentiated, so epidermal cells
give rise to more epidermal cells. In callus culture any cell could
become an epidermal cell or any other organ. Auxin is used to promote
roots, and cytokinin promotes shoots.