Page 151 - phytochemistry general program

To initiate a culture, explants can be taken from any part of the plant. Explant is
cell, organ, or piece of tissue which has been transferred from plants to a nutrient
medium. However explants containing cambial cells exhibit good callus growth
with minimum requirement of exogenous growth regulators. Meristematic cells,

root tips and shoot tips provide good elements to start the culture.

There are different types of cultures which may be classified according to the
organ used e.g. root culture, stem culture, pollen, …etc) or according to the

medium matrix, these are classified into two major classes:

1- Static (solid or stationary) cultures.

2- Suspension (liquid or cell) cultures.

1 - Static (solid or stationary) cultures

These are cultures which grow on agar base in concentration range of 0.6- 1%
W/V. Explants are placed on the surface of agar, after a period of two to three
weeks a callus is formed. A callus consists of an amorphous mass of loosely
arranged parenchyma cells arising from the proliferating cells of the parent tissue.
Frequently as a result of wounding a callus is formed at the cut end of a stem or

root. It is adopted at the beginning of the culture.

General growth of a callus depends on a complex relationship between:

(a)- Plant material used to start the callus.

(b)- Composition of the medium.

(c)- Environmental conditions during the incubation period.

Some cultures growth are heavily lignified and hard in texture, others

are friable. It may appear as whitish, yellowish, greenish or pigmented with

anthocyanins. A homogenous callus consisting entirely of parenchyma cells are
rarely founds, however efforts have been made to achieve uniformity in callus, so

uniform tissue samples can be used as inocula for

biotransformation studies.

Disadvantage of static cultures

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