An embryo is a part of the seed that forms after double fertilization and contains the pre-form of the plant organs. It is cultured in the artificial environment or laboratory conditions in the isolated immature or mature form of an embryo. The plants grown by early culturists, using embryo culture techniques, include Helianthus annuus, Mirabilis jalapa, and Zea mays. The first person to grow these plants was Tieghem, who observed the regeneration of shoots and roots from portions of mutilated embryos. For this purpose, he used excised embryos and grew them in a moist chamber.
The surface sterilization of embryos is not required because it's already packed in the sterile environment of fruit or seed. However, after the collection of the fruit or seed, it is required to send them under surface sterilization. After this, you can safely excise the embryo under a sterile environment for the culturing processes.
If a tough cover is present over seeds, then surface sterilize those seeds with its coat and soak them in sterile water under aseptic conditions. This will loosen the outer covering of the seeds and make the excision of embryos easier than before. However, when you are culturing very small seeds, it's recommended to excise the embryo under a microscope. This will help to protect the embryo from damages that can be caused during excision. In some cases, like orchids and arabidopsis, whole seeds are cultured because of extremely small sizes of seeds.
In this article, you will learn the different categories of embryo culturing and its applications in tissue culture.
Categories of Embryo Culture
- Mature and intact seed embryo culture: It’s to analyze the embryonic growth and metabolic and biochemical aspects of dormancy and germination.
- Surgically dissected embryo culture: In this culture, a mature seed embryo is excised into different segments and cultured to analyze the growth of different parts.
- Immature embryo culture: The immature embryo culture include culturing of globular and heart-shaped stages of the embryo to learn the differentiation and nutrient requirement of progressively developing embryos.
- Intact seeds containing undifferentiated embryo culture: Some seeds, like orchids, don’t have nutritious tissue and lack both plumule and radicle. For these types of seeds, whole seeds with undifferentiated embryos are cultured. For orchids, this technique is a routine procedure for tissue culture propagation.
- Adventitious embryo culture from polyembryonic seeds: The embryos produced from nuclear tissue in plants, like lemon and oranges, are abortive in nature. To avoid this phenomenon, these embryos are cultured under artificial conditions for clonal propagation.
- Inviable and abortive embryo culture: The embryo produced in interspecific and intergeneric breeding are abortive in nature and produce inviable seeds. Embryo culture provides a solution to produce viable seeds and raise hybrid plants.
Embryo Culture Application
- Sterile seeds can be produced using embryo culturing techniques.
- The process of embryo culture is a savior when you need to produce viable embryos from interspecific and intergeneric crosses that generally result in the production of non-viable seeds. For the first time, viable seeds of interspecific plants were obtained by Laibach (1925, 1929) in the interspecific Linum crosses. Laibach excised the embryo of the shrunken fruit and inviable seeds (produced from the interspecific cross) and placed it on the sucrose medium to obtain the germination.
- Micropropagation of hard species is easier using the embryo culturing technique.
- Embryo culture is used for the production of haploids as in the case of Hordeum Vulgare and Hordeum bulbosum.
- Embryo culture is also used to propagate parasitic plants that require a suitable host to complete their life cycle. These plants are called obligatory parasites. These plants die if they don’t find a suitable host to fulfill their requirement.
- Some seeds are present in dormant conditions and they require a specific climate for their germination. This phenomenon handicaps the horticulture work as well because these seeds take several years for their germination. The solution to this problem is the embryo culture. This technique has also been found to be useful in shortening the breeding cycle of deciduous trees and increasing the germination ability of hybrid embryos.
- Embryo culture has been a useful tool to study the effect of vernalization or cold treatments in plants.
- Embryo culture is also used to produce pathogen-free or virus-free plants.
- Narayanaswami, S., & Norstog, K. (1964). Plant embryo culture. The Botanical Review, 30(4), 587–628. doi:10.1007/bf02858652
- Bhatia, S. (2015). Plant Tissue Culture. Modern Applications of Plant Biotechnology in Pharmaceutical Sciences, 31–107. doi:10.1016/b978-0-12-802221-4.00002-9
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