Plant tissue culture : a short overview

In the current day and age, plant tissue culture is a popular scientific technique being followed by curious kitchen gardeners to renowned scientists from laboratories around the globe. It is both an art and science, in which multiplication of plant cells, tissues, organs, protoplasts and so forth, is done to form whole plants. Surprisingly, there is a huge proportion of people who are still not aware of plant tissue culture. Some people get curious when they come across tissue culture, what is it? How is it done? Who is doing it and why? Some people even ask if they can try themselves. Should they even try? What are the costs involved in building a laboratory? What are the best resources for building it? What are the potential financial revenues? What are the risks involved? Hence, we are starting our series of blog posts as an attempt to answer these questions and bring more light to the fascinating world of plant tissue culture!

The famous plant tissue culture

There are several methods developed for growing plants. For instance, we already know that plants grow in fields from seeds. Then there are other methods like vegetative propagation where stem cuttings, tubers, etc. of different plants are used to grow and propagate in soil. These methods in general take a longer duration to grow with specific soil conditions that need to be present along with other factors. This is where tissue culture steps in to enhance the growth without the above-mentioned restrictions. It may sound complicated, however, tissue culture is an easy-to-follow process. Under this technique, a piece of plant is taken, and it could be anything from a portion of stem, root, leaf or bud to merely a single cell. This piece is placed in a tiny quasi ‘greenhouse’ such as a test tube or culture vessel along with a balanced diet of growth-enhancing biochemicals / plant hormones resembling the plant’s original nutrient composition. This little piece in that tiny ‘greenhouse’ is called an ‘explant’ which will develop into several tiny, yet complete plant systems known as ‘plantlets’. This entire process is possible as plant cells have an amazing ability to differentiate into other cell types and this quality is known as ‘totipotency’.

Plant protection

For the successful development of healthy plantlets, it is necessary to create a sterile environment, free from living contaminants such as microorganisms, mites, insects and so on. As conventional plants growing in field conditions, these ‘greenhouses’ are quite susceptible to get fungal or bacterial infections and die due to diseases. In order to prevent this scenario, a balanced diet of chemicals is also supplied with biological antibiotics when required.

Multiplication in large numbers

One of the fascinating features of tissue culture is that each plantlet continues to produce and maintain small stems and leaves throughout its duration. Also, each plantlet developed is identical to other plantlets and to the mother plant, unlike the non- identical plants produced from seeds or cuttings. From a single explant, hundreds of new shoots can be developed which can be further developed into full growing individual plants in field conditions. This quality of plant tissue culture is being exploited industrially for meeting the demands to obtain parts of plants or identical plants in large numbers ('millions').

Growth stages and conditions of plant tissue culture

The process of development of a complete plant system, from selecting the explants to transferring the plantlets to normal field conditions consists of 5 basic stages: Stage 0 – stock plant selection and preparation; Stage 1 – establishment of aseptic cultures (disinfection); Stage 2 – multiplication; Stage 3 – in vitro rooting; and Stage 4 – transplanting and acclimatization (Hardening off). These stages can overlap and for each stage the requirements are different. Also, there are different controlled conditions required for culturing different species, varieties, cultivars and so on. Also, with each species, the composition of balanced chemicals supplied for growth changes, depending on the needs of the specific variety. The crucial conditions that influence the results of tissue culture are:

• Temperature: optimal range of temperature for successful development of plantlets (depends on the considered plant species);
• Humidity: in tissue culture, the relative humidity (RH) is generally 95 - 99%;
• Photoperiod: duration of light and dark period necessary for optimal plant growth (14 – 16 hours of light);
• Light intensity: gradation in light intensity required for tissue culture; and
• Nutrient medium: a mixture of inorganic salts, a carbon source, some vitamins, growth regulators and most of the time agar, that acts as substrate for efficient plant growth.

More about these conditions in upcoming blogs! After hardening off the culture grown plants, they are transferred to field conditions, where the plantlets produce normal leaves and assume the mature features of the plants from which they originated. In a nutshell, tissue culture has been widely used in several industries for decades now. However, for many industries like one of those booming now, for example, the cannabis industry, plant tissue culture is being adapted for large scale productions of good quality end products. Hence, there is extensive research going on in order to map its potential in all possible sectors of agriculture.

References

1. Jo, E. A., Tewari, R. K., Hahn, E. J., & Paek, K. Y. (2008). Effect of photoperiod and light intensity on in vitro propagation of Alocasia amazonica. Plant Biotechnology Reports, 2(3), 207–212. https://doi.org/10.1007/s11816-008-0063-6
2. Debergh, P., De Riek, J., & Matthys, D. (1994). Nutrient supply and growth of plants in culture. In Lumsden P.J., Nicholas J.R., Davies W.J. (eds) Physiology, Growth and Development of Plants in Culture. (pp. 58–68). Springer, Dordrecht. https://doi.org/https://doi.org/10.1007/978-94-011-0790-7_5
3. Plant Tissue Culture. (n.d.). Retrieved from https://www.sciencedirect.com/topics/biochemistry-genetics-and-molecular-biology/plant-tissue-culture
4. Bhojwani, S. S., & Dantu, P. K. (2013). Plant Tissue Culture: An Introductory Text. https://doi.org/https://doi.org/10.1007/978-81-322-1026-9
5. Javeria, F. (2020). What is the intensity of light, required for plant tissue culture? Retrieved from https://www.researchgate.net/post/What-is-the-intensity-of-light-required-for-plant-tissue-culture