Page 152 - phytochemistry general program

Although most of the tissue culture laboratories adopt the static culture at the
beginning of their work, however, there are some difficulties which may arise

during the growth, e.g.
1- Prolonged culture periods may lead to chromosomal changes and gene
mutation. This is a major problem in P.T.C. specially in application to genetic and

plant breeding.
2- The non-homogenous growth of the cells will harden the process of subculturing

into a new media.
3- The toxic metabolites may accumulate without being diluted.

4- Gradient nutrient deficiency may occur.
5- The agar used may release undefined toxic substances to the callus.

2- Suspension (liquid or cell) cultures
These are cultures grown on aqueous media provided with necessary
components for growth. Cultures are initiated by either transferring fragments of
undifferentiated callus or explant of differentiated plant material to liquid
medium which is then agitated. The dividing cells will gradually free themselves

from the inoculum because of the swirling action of the liquid.
A good suspension culture is that consisting of high percentage of single cells and

small cell lumps.
Cell suspension cultures must be agitated continuously for aeration, using a

platform shakers or magnetic stirrers.

Advantages of suspension cultures
1- Suspension cultures have faster growth rate than solid cultures.
2-The cultures are homogenous hence more suitable for the biotransformation

studies and production of secondary metabolites.
3- The toxic metabolites are continuously diluted.
4- No gradient nutrient deficiency as the elements are homogeneously

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