Propagation by tissue culture follows several detailed steps. The first few steps occur in a lab, where plant material is initiated, multiplied and elongated. At the end of the lab period, most of our plantlets are moved out to our greenhouses for rooting under frequent misting.
Simply put, tissue culture is the process of taking a small piece of plant tissue and placing it in a sterile container filled with carefully prepared media, free of micro-organisms. The media contains the correct balance of chemicals and growth hormones to create a tiny replica of the parent plant.
Tissue culture can be used for many reasons – to quickly produce large quantities of genetically identical plants; to produce plants that don’t propagate well with other means; to establish and maintain virus-free stock. We use tissue culture for the first two reasons. From a small piece of plant tissue, we can produce a marketable plant in less than a year. And if we start out with a plant with desirable characteristics, we can maintain those traits in the offspring plants for several generations.
Sterile techniques are the rule. Any contamination can infect and destroy the cultures, which will reduce the number of plants we have to sell for many months. Some people have asked if they can tour our lab facility and, unfortunately, we have to tell them no. There is a high risk of contamination – even most of our nursery staff will not be permitted in the tissue culture lab. We will, however, add photos of our lab activities on this website.
The Tissue Culture Process
We have been continuing on with propagating DNA Garden’s plant material so we can provide hardy plant material to our customers.
Stage 1 Initiation
We take a piece of plant tissue (bud, leaf, stem or root) and disinfect it as much as possible using sterile water, bleach and alcohol. All of this work takes place in a laminar flow hood in the lab. This hood forces sterile air over the transfer area so there’s less chance of bacteria and fungi coming in contact with the plant tissue. Bacteria and fungi can grow quickly in the tissue culture containers as what is good for plant growth is also grow for microbial growth.
Stage 2 Multiplication
The cleaned pieces of plant tissue are placed in sterile containers that contain media with all the ingredients needed for the tissue develop into a plant. The media contains nutrients, plant hormones, an energy source (such as sugar), water and a thickener to make the media gel. In Stage 2, we want the plants to produce several leafy shoots on a clump of cells called a base or callus tissue. After about 2 weeks, the cultures need to be transferred to new containers and media as they used up what was in the initial containers.
This is when you can see the how quickly plants can multiply. Plants grow quickly in tissue culture and they are divided each time they are transferred so 1 plant = 3 plants = 9 plants = 27 plants = 81 plants and so on until you have the number of plants you need.
Stage 3 Elongation
Plants are transferred once again, in the laminar flow hood, onto a medium that makes the shoots elongate. This is the stage where the stems of the plants grow in length and begin to resemble little plants.
Stage 4 Pre-Rooting
This can happen in the tissue culture lab or in the greenhouse, depending on the species. The elongated shoots are trimmed off the base tissue and placed on to media that contain auxins, for rooting. Once roots are visible, the plants can then be planted into the greenhouse. Plants coming from the lab environment have been grown at high relative humidities and are very tender. They have to be watched very closely when they are moved to the greenhouse to make sure they are acclimatizing properly.