Plant Tissue Culture - Asexual/vegetative Propagation

Plant Tissue Culture

In plant breeding the technique of tissue culture has emerged as a really economical tool to propagate higher improved crops. Tissue culture as a more accessible technique than other traditional plant breeding techniques. Using this method, cells, tissues, etc. are kept in the artificial medium in septic conditions in vitro and develop, which provides the necessary nutrients for growth. In 1839 Schleiden and Schwann proposed that the cell is the basic unit of life and is capable of autonomy. Every cell in the environment has the ability to regenerate into the whole new plant. Based on this theory, Gottlieb Heberland, a German physiologist, developed the concept of in vitro cell culture in 1902, also known as tissue culture.

In his experiment, the cells increased in size but failed to divide, which led to the failure of his predictions. However, his hypothesis paved the way for further research. Thus he is considered the father of tissue culture. In 1997, Henning took a cue from his experiments when he took an almost mature embryo of the crucifixion and successfully increased his maturity.

In 1988, Simon regenerated callus shoots and roots from poplar stem segments and laid the foundation for callus cultivation. In 1934 a breakthrough came from white who experimented with tomato roots. He reported that not only could the root tips of cultivated tomatoes grow, but they could also be repeatedly subcultured in the fresh medium of inorganic salts supplemented with yeast extract. During the 1950s, scientists discovered that any part of a plant grown in a nutrient medium under sterile conditions can give rise to a completely new plant. The part of the plant used in culture is known as ex-plant. This property of plant cells to give rise to a completely new plant is called totipotency. In 1968, the term totipotency was coined by Stuart.

Totipotency

It requires a nutritional medium that contains sucrose, inorganic soles, vitamins, proteins, and growth regulators such as auxins and cytokinins.

The technique of tissue culture

The first step in tissue culture is to exercise or cut a small part of the plant tissue such as the root of the leaf or the shoot of a plant. This cut out the part, ex-plant, is then placed in a suitable nutrient medium containing a carbon source such as sucrose, inorganic salts, vitamins amino acids, and growth regulators like auxins, cytokinins, etc. The ex-plants are allowed to multiply and form a group of tissues called a callus. A callus is an irregular, disorganized, and undifferentiated mass of actively dividing cells. This callus is then allowed to multiply to form numerous plantlets which are then transferred to a different container for fast multiplication. Finally, the developed plant is transplanted to the soil the normal growth. Tissue culture was performed using a small part of a plant to grow a large number of plants in a short duration, which is why it is also called micropropagation. Since all these plants develop from the same part of the mother plant, they are genetically identical and are called somaclones.

Micropropagation is widely used in horticulture and floriculture and is used in the large-scale production of tomato, banana, apple, etc. This technique can also be used to propagate high-yielding disease-resistant varieties in a short period. Even under conditions where the plant is diseased, tissue culture is reduced to recover healthy plants from diseased plants by taking the ex-plant plant from the apical or axillary meristem. This is done because the meristem is always free of pathogens due to a lack of vascular supply. The process of using the meristem for propagation is called Meristem Culture. The cultivation of a meristem has been carried out with success in plants such as banana, sugar cane, and potato.

Advantages of Tissue Culture

Tissue culture has many benefits which are given below:

• A large number of plants can be grown in a short time
• Healthy plants can be produced from diseased plants.
• Plants without the can be multiplied.
• It is useful where sexual reproduction is not possible.