Page 156 - phytochemistry general program

years were required to reach this goal as compared with about six years needed
with ordinary breeding methods.

4- To induce genetic variation of the regenerated plant to produce some desired
characters as salt resistance or cold resistance.

II)- Tissue culture as a source of pharmacologically important secondary
metabolites.

Totipotency of the plant cell shows that all the necessary genetic and physiological
potential for product formation must be present. It is the role of the scientist to find
the right conditions for the cells to produce and store the required secondary
metabolites. Despite the advances in the field of organic chemistry, plants still an
important commercial source of chemical and medicinal compounds. Secondary
metabolites are compounds unique to a few species, these substances include

volatile oils, tannins, sterols, flavonoids, glycosides, alkaloids, etc.

Medicinal plants growing in different ecological zones have been exploited to such
an extent that their natural reproduction in their native areas cannot be assured

any more, this is due to many factors such as:

a- Unsure supplies due to political problems, weather disasters etc.

b- Lack of standardization, the production of crude drugs is subject to the vagaries
of the climate, to crop disease, to varying methods of collection and drying which
influence quality, and to the inherent variation of active constituents arising from

plants of the same species having different genetical characteristics.

c- Adultration through mixing with drugs of low varieties or exhausted material.

P.T.C has been hopefully considered as an alternative source to agricultural
production. It can even offer the possibility for the production of novel compounds
not found in plants. By optimizing the conditions, many workers have been
successful in having cultures which produce products in amounts equal to or
greater than those present in intact plant, examples of there compounds are,
diosgenin, caffeine, visnagin and anthraquinone. On commercial level compounds
such as ajmalicine (for circulatory disorders), shikonin (for skin diseases and

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