Tissue culture

Biotechnology is used in farming, medicine, food processing and more. Research in it has three aims: finding the best catalyst (the best organism or enzyme for the job), creating the best conditions for it to work, and improving downstream processing to purify the product.

Why farming needs it. The Green Revolution used improved crop varieties, fertilisers and pesticides, and helped triple the world's food supply. But the population keeps growing, conventional breeding is slow, and fertilisers and pesticides are costly and can harm the environment. Biotechnology offers new ways to grow more food.

Plant tissue culture rests on a remarkable ability of plant cells: totipotency, the capacity of any living plant cell, or a small piece of plant tissue (an explant), to grow into a whole new plant.

The explant is grown in a sterile nutrient medium, outside the plant (in vitro). The medium contains a carbon source such as sucrose, inorganic salts, vitamins, amino acids, and the growth regulators auxins and cytokinins.

Its uses:

• Micropropagation: thousands of plants can be grown in a short time from small explants. Because they come from one parent without sexual reproduction, they are genetically identical: they are called somaclones. Tomato, banana and apple are produced commercially this way.
• Virus-free plants: even when a plant is infected by a virus, its growing tips, the apical and axillary meristems, remain free of virus. Growing a plant from a meristem gives a healthy, virus-free plant. This has been done with banana, sugarcane and potato.
• Somatic hybrids: plant cells are stripped of their cell walls to give naked protoplasts. Protoplasts of two different varieties can be fused, giving a hybrid cell that grows into a new plant. Pomato, a hybrid of tomato and potato, was made this way. It did not have all the qualities needed to be grown commercially, but it showed what is possible.