25 Feb 2021

In Vitro Seed Germination of Orchids

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

Orchids For Beginners

Orchids are one of the most beautiful flowering plants belonging to the family of Orchidaceae. Approximately 25,000 species of orchids reside in the Orchidaceae family that includes a range of flowering plants with different beautiful structures and variant colors. Which Orchid crosses your mind when anyone talks about Orchids?

These plants are at risk of genetic loss due to their over-harvesting and illegal trade. Multiple techniques (ex vitro and in vitro) are being developed to conserve the genetic integrity of these beautiful plants. This article discusses the factors that determine the healthy growth of the plant in ex vitro conditions and the in vitro seed germination technique of orchids. Scientists are extensively using this technique to conserve and mass propagate the orchid plants. So, let’s begin!

Some awesome facts about Orchids

Orchids belong to the family of Orchidaceae that includes 25,000 species of plants (70% are epiphytes-plants that grow on another plant). It’s the largest family of flowering plants. These plants are spread in almost every part of the world. Orchids are valued across every continent, from Arctic Circle to the southernmost jungle (except Antarctica). The flower size of the plant varies from species to species. The smalled Orchid is of dime-size!! Isn’t it lovely!

The seeds of the Orchids are the tiniest seeds in the world. Moreover, the seedpod of Orchids contains around 3 million seeds (that have no endosperm and nutrients within). Certain species of Orchids are parasitic and they obtain their nutrients from the fungus that live in their roots. The most interesting fact about Orchids is that according to fossils evidence, Orchids have existed on the planet around 100 million years ago!!

What are the factors that determine the growth of the Orchids?

The key point to be kept in mind while growing Orchids is to know which Orchid you are growing and its cultural requirements. This will help you to maintain the plant, leading to higher output and healthy growth. The three main elements that determine the growth of Orchid plants are the balance of light, water, and food. To produce Orchids in lush and bloom, the optimum amount of light should be provided. Too little light will result in dark green leaves and will prevent plants to bloom. When sufficient light is provided, the flowers bloom and the leaves are light green or yellow-green in color.

The potting medium of the Orchids should have proper drainage and good aeration. This keeps the roots of the plant (eventually the plant) healthy! Avoid overwatering of the plant as it will lead to root loss. This will result in the death of plants. While watering Orchids, it’s necessary to check the moisture content in the medium and accordingly add water. Keep in mind the size of the pot as well while watering as this will help you to determine how much water you should add to the plants.

Tissue culture of orchids

Tissue culture is a popular and extensively used technique for the mass production of orchids among orchid breeders. However, the culture medium, environmental conditions, and climatic factors required for the healthy growth of orchids are different for different plant species. So, you must understand the requirements of your plant before you go ahead with the culturing process.

Because the seeds of the orchids are very small and there is no nutritional content present in them, it’s very difficult to propagate orchids through seeds. Naturally, it takes years (between 2-8 years) for orchids to develop as a whole blooming plant when grown from seeds. For this reason, tissue culture has been a proven successful technique to grow orchids in a short time.

Today, orchids are grown in vitro from different explants like leaf segments/tissues, flower stalk nodes, callus and protocorm-like bodies, flower stalks, and seeds. But in this article, you will be learning how to propagate orchids through seeds.

In vitro seed germination of Orchids

The success of in vitro seed germination depends on several factors including culture media, seed maturity, plant growth regulators, carbohydrates, and organic nutrients. This section will discuss the procedure of seeds germination of Phalaenopsis amboinensis (the moth orchid). The study is taken from “Edy Setiti Wida Utami, Sucipto Hariyanto, "In Vitro Seed Germination and Seedling Development of a Rare Indonesian Native Orchid Phalaenopsis amboinensis J.J.Sm", Scientifica”.

Figure: A flower of Phalaenopsis amboinensis (the moth orchid) 

Procedure

1. Collect the mother plant from which seeds need to be isolated.
2. Take the yellowish-green capsule and wash it with a soapy solution for 5 minutes to eliminate the dust particles from its surface.
3. Then, rinse the capsule with sterile distilled water and keep it in the laminar hood in a petri dish.
4. Flame the capsule containing the petri dish three times. Here, complete surface sterilization of the capsule is done!
5. To isolate the seeds from the capsule, cut the capsule longitudinally into two halves using a sterile razor blade in a sterile Petri dish.
6. Prepare the Vacin and Went (VW) media and supplement it with 30 grams/liter of sucrose and 3 grams/liter of peptone. Adjust the pH of the medium to 5.6.
7. Then, add 2 grams/liter gellan gum to the prepared media to solidify.
8. Sterilize the medium at 120°C for 15 minutes.
9. In a culture tube, pours 25 ml media which can hold 300 orchid seeds.
10. Maintain the cultures under 16 and 8 hours light and darkness, respectively, at 23 ± 2°C.
11. After 10 weeks of culture, you will obtain a plantlet of 0.5 cm in size with 1 or 2 leaves and one root.
12. Then, transfer the plantlet to the fresh Vacin and Went (VW) media supplemented with 15% coconut water (v/v) and banana homogenate (10 grams/liter).
13. Maintain the cultures under 16 and 8 hours light and darkness, at 23 ± 2°C.
14. When the in vitro plantlets are developed with well-developed roots remove them from culture and wash under running tap water.
15. Transfer the plantlets to culture pots containing a mixture of coal pieces : tree fern roots : sphagnum moss at a 1 : 1 : 1 ratio.
16. Keep the plants in the greenhouse under 30%–40% natural light and spray twice a day with water for acclimatization.

The tissue culture of orchids is best if you are trying to conserve these plants or want to grow them in huge numbers for commercial purposes. Let us know how your orchid culture goes. Till then happy culturing!!

References

1. Edy Setiti Wida Utami, Sucipto Hariyanto, "In Vitro Seed Germination and Seedling Development of a Rare Indonesian Native Orchid Phalaenopsis amboinensis J.J.Sm", Scientifica, vol. 2019, Article ID 8105138, 6 pages, 2019. https://doi.org/10.1155/2019/8105138
2. Diantina, S., Kartikaningrum, S., McCormick, A.C. et al. Comparative in vitro seed germination and seedling development in tropical and temperate epiphytic and temperate terrestrial orchids. Plant Cell Tiss Organ Cult 143, 619–633 (2020). https://doi.org/10.1007/s11240-020-01947-7
3. https://plainviewpure.com/12-incredible-orchid-facts-no-one-ever-told/
4. https://www.flowerweb.com/en/article/190242/15-Amazing-Facts-About-Orchids
5. https://www.aos.org/orchids/orchid-care/orchids-10...