I was recently invited to a housewarming party and was looking for a nice gift. As a plant lover, I had no choice but to visit my local garden center. Then you stand there in the middle of the center, looking in admiration at the orchids, lilies and lilies, displayed in order of color and size. I think most people have asked themselves this question at some point: How do all these plants look so similar? …a question with a surprisingly simple answer, these plants were most likely clonally propagated in the laboratory. Clonal reproduction ensures that all plants are copies of each other and look exactly the same. For many plants today this is done mainly via a “test tube” in the laboratory.
Generative reproduction
When you think of propagating plants, the story of flowers and bees undoubtedly comes to mind. The flower produces pollen, which spreads to other flowers, sometimes with the help of bees. There, the pollen can then fertilize the flower's egg, which produces a seed after a period of waiting. Plants grown from seeds often look different from their parent plants. Although the apple does not fall far from the tree, it will never be the same tree. We call this generative reproduction because it creates a new generation of plants.
In nature, it is often good to have as much diversity as possible, as this ensures that plants can better adapt to new conditions. If you, as a garden center, want to sell a particular “example” of a popular plant, it is best to sell all identical plants. Fortunately, many plants have a second system for bringing new plants into the world: vegetative reproduction. Humans use this natural system to clone animals in the field or in the laboratory.
Vegetative propagation
In vegetative propagation, the plant alone makes a copy of itself. Think strawberry sprouts, growing potatoes or garlic cloves. In many plants, the vegetative reproductive system is so powerful that roots spontaneously begin to grow on a pruned branch upon contact with water or soil. Over time, this branch grows into a new shrub or tree. We call this procedure “cutting” the plant. If you want to try it yourself, willow is the perfect plant to start with.
However, this system is not created equally in every plant and a pruned branch sometimes needs some help. In this way you can also “graft” the pruned branch. Grafting involves attaching a branch from the tree you want to clone to an existing plant so that they grow together. The existing rooted plant can then provide energy to the branch, which can then continue to grow. Many of our fruits, such as apples and pears, are propagated this way so that all Jonagold or Green Stars taste the same. But now you may be wondering, why is this lab still necessary?
Faster and cheaper
Well, sometimes this system is weaker. Think tropical orchids. In nature, but also on the windowsill, these plants exceptionally form a new plant through vegetative propagation. In the laboratory, they can help these plants do this on a much larger scale, in a fast and cheap way. While in the past tropical orchids were reserved only for the elite, with prices rising to over €1,000 (converted), today you can buy a specimen for just €5. This technology has also significantly reduced the prices of other houseplants, allowing everyone to enjoy all their splendor at home.
But how is it done? In the laboratory, we pamper our plants by placing them on a nutrient medium that contains all the essential nutrients for optimal growth. We also add plant growth regulators. These growth regulators work just like hormones in animals and control plant growth and development. Adding more cytokinin temporarily awakens dormant nodules that grow into clonal shoots, and these new shoots are then separated from the mother plant and prepared to stand on their feet at your local garden center. This growth-regulating effect is only temporary, because once the plant is removed from its breeding ground, it regains its natural balance.
research
Can we simply propagate all the plants in the laboratory? Before the plant can be widely disseminated, a lot of research is needed. Every plant has its own desire. For example, the composition of essential nutrients and plant growth regulators varies from plant to plant. It may take years to uncover this perfect balance. For example, I worked with my colleagues for 3 years to develop a coconut propagation protocol. In addition to adding cytokinins to create new shoots in vitro, there are other methods such as cell suspensions and somatic embryogenesis that all use systems naturally present in the plant. Fortunately, major networks like COPYTREE (https://www.copytree.eu/) plant breeders and researchers together, so they can share their experiences with each other and work together to find solutions.
Have you become interested in propagating these beautiful houseplants on your windowsill? This shouldn't be as difficult as it is for test tube factories. Online you will find many tips and tricks on cutting your favorite plant. After reading this text, you can ask friends or family on your next visit: “Do you already have a test tube factory at home?”
Sources and links
• Wilms, H., De Bièvre, D., Longin, K. et al. Development of the first in vitro axillary bud propagation protocol for coconut palms. Sci Rep 11, 18367 (2021). https://doi.org/10.1038/s41598-021-97718-1
