35.6: Plant Tissue Culture
Plant tissue culture is widely used in both primary and applied science. Applications range from plant development studies to functional gene studies, crop improvement, commercial micropropagation, virus elimination, and conservation of rare species.
Plant tissue culture depends on the ability of plant tissue to give rise to an entire new plant when provided with a growth medium and appropriate environment. This ability of plant cells or tissues is termed ‘totipotency.’
The fundamental steps of plant tissue culture are fourfold:
- Select a healthy parent plant (explant).
- Eliminate any microbial contamination from any exposed explant surfaces.
- Inoculation the explant in an adequate culture medium.
- Incubation of the explant in a controlled environment with appropriate temperature, humidity, air quality, and illumination.
There are also four different types of plant tissue culture, which may be chosen based upon the goals of the culture, or plant species:
- cell culture (such as gametic cells, cell suspension, and protoplast culture).
- tissue culture (callus and differentiated tissues).
- organ culture (any organs such as roots, shoots, and anthers).
One of the popular applications of plant tissue culture is the in vitro clonal propagation - also known as micropropagation. Plant tissue culture, in this case, can aid in the reproduction of plants that have problems with seed germination (recalcitrant plants), or have short-seed viability. Although micropropagation can be applied to any species, it is recommended for commercially essential plants or those at risk of extinction. For example, micropropagation is widely used for the cultivation of orchids such as Paphiopedilum delenatii - a species native to the Himalayas. These orchids are traditionally propagated through seeds. However, it takes about 2-3 years for mature orchids to produce these. Therefore, plant tissue culture has become an ideal method to protect this species from extinction and achieve commercial viability.
Micropropagation can be carried out in three different ways:
- using an apical or axillary bud.
- using the adventitious bud.
- through the formation of a somatic embryo, using somatic parent plant cells.
The success of each of the techniques depends on the genetic background, culture media, and incubation conditions.