16 Feb 2021

Tissue Culture Application of Photoautotrophic Micropropagation

Anjali Singh, MS

As a content and community manager, I leverage my expertise in plant biotechnology, passion for tissue culture, and writing skills to create compelling articles, simplifying intricate scientific concepts, and address your inquiries. As a dedicated science communicator, I strive to spark curiosity and foster a love for science in my audience.

Table of Contents

Introducing Photoautotrophic Micropropagation

We have discussed micropropagation many times without touching on the meaning of “photoautotrophic micropropagation" and how this specific kind of micropropagation can benefit your tissue culture. If this term and technique is something unknown to you, this article will help you to grasp the essence of photoautotrophic micropropagation and the advantages of this technique.

First, let’s understand the meaning of the word by splitting it into two parts: photoautotrophic and micropropagation. Photoautotrophic means an organism that is capable of making its food using “inorganic nutrients” in the presence of light as an energy source. And micropropagation is a technique of developing genetically identical plants under favorable artificial conditions. So, how do you define photoautotrophic micropropagation as a whole! Let’s learn about the technique sequentially: the definition, how it works, full advantages / disadvantages

Photoautotrophic Micropropagation Explained (Definition)

Photoautotrophic micropropagation is a technique in which micropropagation is performed without sugar and organic nutrients in the medium. No amount of organic nutrient is added to the medium from outside. Vitamins, growth regulators, and even gelling agents are not added to the medium. In photoautotrophic micropropagation, gelling agents in the medium are replaced by porous substances like vermiculite.

In this system, no amount of sugar component is added to the growth media exogenously. Instead, the requirement of sugar is fulfilled by the amount of endogenous carbohydrate present in tissues. Efficient practice and handling are required while using this tissue culture technique. Photoautotrophic micropropagation requires a good level of understanding of in vitro environment and basics of environment control.

You may wonder if vitamins, sugar, and growth hormones are not used in this technique, what promotes the proper growth of plants?! How do plants develop on their own? The major dependency of this technique is on photosynthesis. The growth rate of plants can be enhanced by enhancing the photosynthetic rate of plants. How is this done? The process is completed by understanding the environmental status in the culture vessels (ex: air temperature and CO2 concentration). You should also understand how to maintain the optimum level of these environmental factors to enhance the photosynthetic rate of the plants.

Stages in Photoautotrophic Micropropagation

Conventional micropropagation has four stages: (I) initiation, (II) multiplication, (III) rooting/preparation, and (IV) acclimatization. However, photoautotrophic micropropagation consists of only two stages:

1. Induction/initiation stage of the culture: In this stage, a virus-free (or pathogen-free) culture is established by culturing meristematic tissue (it is generally free from viral infections and safer to culture). This stage is either heterotrophic/photo mixotrophic in which cultures can utilize endogenous or exogenous supplied nutrients. In this stage, the cultures develop proper photosynthetic organs after which they are transferred to complete photoautotrophic micropropagation conditions.
2. Multiplication/rooting stage: Unlike conventional micropropagation, the multiplication and rooting stages are combined in photoautotrophic micropropagation. It’s done by reproducing photosynthetically active, leafy nodal cuttings that are used as explants.

In Vitro Environmental Conditions Required for Photoautotrophic Micropropagation

The physical conditions of the culture vessels are essential to monitor and operate. It includes the physical properties of the vessels and plantlets. Requirements include:

1. low CO2 concentration during the photoperiod
2. high CO2 concentration during the dark period
3. low water vapor pressure deficit (high relative humidity)
4. low air current speed
5. low photosynthetic photon flux (PPF): photosynthetic photon flux is the amount of light energy used by photosynthetic organisms in photosynthesis. It occurs in the range of 400-700 nm.

Advantages of photoautotrophic micropropagation

So far you have learned the basic concept of photoautotrophic micropropagation. But, you may ask why shall you use this technique? How will it help you? Listed below are some of the advantages of photoautotrophic micropropagation.

1. It promotes the growth and photosynthesis of in vitro plants.
2. It prevents morphological and physiological disorders.
3. It decreases the microbial contamination inside the culture vessel.
4. It shortens the in vitro plant multiplication cycle.
5. The survival rate of in vitro plants in this case is higher when transferred to an ex vitro environment.
6. The technique simplifies the micropropagation process by reducing its stages.
7. The design of the culture vessel used in this technique is more flexible for large-scale in vitro plant production.
8. It reduces the labor cost.
9. It makes the automation process of the culture system easier.

Disadvantages of photoautotrophic micropropagation

1. The operation of this technique requires good knowledge of the physical in vitro environment of the systems.
2. The cost of CO2 enrichment or use of gas-permeable filter discs to increase CO2 concentration in the vessels, lighting, and cooling, is higher. This makes this technique a bit pricey.
3. The technique has limited application to a multiplication system when using multi-shoots or plants having C4 or CAM photosynthesis pathways.

We will go in-depth to all these points in our further articles and will talk more about how to maintain the perfect culture condition and control the environmental factors when you are culturing plants using this technique. Until then, happy culturing!!

References

1. Nguyen, Q. T., Xiao, Y., & Kozai, T. (2016). Photoautotrophic Micropropagation. Plant Factory, 271–283. doi:10.1016/b978-0-12-801775-3.00020-2.
2. Kubota, C. (2001). Concepts and Background of Photoautotrophic Micropropagation. Molecular Breeding of Woody Plants, Proceedings of the International Wood Biotechnology Symposium (IWBS), 325–334. doi:10.1016/s0921-0423(01)80089-7.
3. https://www.researchgate.net/publication/225427699...