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Lesson: Chapter 14 — Continuity of Life

14.2. Artificial vegetative propagation 7 of 8

Tissue culture

Any piece of living vegetative tissue obtained from a plant can be cultured in a growth medium under controlled conditions to produce new plants that are genetically identical to the mother plant. New plants obtained in this way are called a clone.

For this, tissue is generally taken from meristematic places such as the apical bud, the lateral bud and the root tip — the regions where cells are still dividing and have not yet committed to being one thing.

The growth medium

The medium used for tissue culture contains sucrose, mineral salts, vitamins and growth substances. Agar is used to bring the medium to a gelatinous state.

To make tissue culture successful, sterile conditions must be created, and conditions such as temperature and light must be controlled. A single bacterium or fungal spore in the flask will outgrow the plant tissue and the culture is lost.

The main steps followed in tissue culture

  1. Placing the piece of vegetative tissue obtained from the mother plant in the growth medium.
  2. A new tissue called callus forms on the piece of vegetative tissue, and new roots and shoots are allowed to grow from that callus.
  3. Separating the shoots and placing them in test tubes to grow further.
  4. Placing the shoots so that they harden, suited to the environment, in a way that fits them for cultivation.

Figure to be added

Figure 14.5 — the steps of tissue culture, from a carrot through the tissue piece in its dish, the callus in the flask, the shoots in culture and the hardened plants in a tray.

The following advantages can be gained through plant tissue culture:

  • being able to produce daughter plants with characteristics identical to the mother plant;
  • being able to obtain a large number of plants at one time;
  • being able to obtain a large number of plants within a short time;
  • being able to propagate a large number of healthy plants within a small space;
  • being able to obtain a large number of new plants by culturing a piece of tissue from a hybrid plant carrying a beneficial gene.

Assignment 14.2

  • Using various sources, prepare a list of the places where tissue culture is carried out in Sri Lanka.
  • If you have the opportunity, make a field visit to such a place and study the tissue culture process.
  • Name the plants most widely produced by tissue culture in Sri Lanka.