What is tissue culture?
Plant tissue culture is a collection of techniques used to maintain or grow plant cells, tissues, or organs under sterile conditions on a nutrient culture medium of known composition. It is widely used to produce clones of a plant in a method known as micropropagation
Tissue cultures are formed by taking a tiny piece of plant tissue such as a stem tip or meristem and placing it in a sterile nutrient medium, sometimes containing plant hormones. The plant tissue is then incubated under artificial lighting to produce clones of the parent material.
For non-variegated plants and plants with “stable” variegation, micropropagation is a very viable method to produce large quantities of a given plant. The challenge comes when trying to propagate chimeras. Chimera, also spelled Chimaera, in botany, is a plant or plant part that is a mixture of two or more genetically different types of cells.
Chimeras may also arise by a mutation in cells of a growing region. The new kind of tissue may be conspicuously different from the old (as when it is colorless instead of being green), but far more commonly the difference is evident only on special investigation, as when the number of chromosomes is altered.
Plants such as the Philodendron Caramel Marble, the Philodendron Florida Beauty, or the Philodendron Billietiae Variegated are popular chimera plants. Due to this challenge to produce large quantities using tissue culture, the prices of these plants remain high.
Tissue culture has been a popular method of propagating wild mushrooms, carnivorous plants as well as other plants such as hemp by home enthusiasts. With the rise in popularity of houseplants, tissue culture has seen a rise in popularity among more hobbyists in order to propagate rare plants.
This plant form allows for the rapid propagation of plants and is an ideal method for transporting plants between countries.
How to Acclimate Tissue Culture Plants?
Acclimatization is the adaptation of organisms to a new environment. When tissue culture plants are transferred from the lab to soil they are exposed to abiotic stresses, like altered temperature, light intensity, and humidity conditions, and biotic stresses, like soil microflora (microbes living in soil). So, they need step-wise acclimatization to successfully establish themselves in the natural environment.
When you receive your tissue culture plants you will see that they have proper roots however some plants don’t form roots in tissue culture. But when you plant them out, they form roots within weeks. So please do not get alarmed if your tissue culture plants don’t have any roots.
We will come with a step-by-step guide to help you be successful in growing them. In the meantime, to get you started here is a quick list of materials that you will need:
I. After Receiving
Open the flask (plastic container) in a shaded, cool, and most importantly, clean environment.
Carefully remove the plants and rinse off any gel remaining on the roots. It is important that this is removed, as it will encourage fungal growth once exposed to non-sterile conditions. A useful technique is to open the flask and pour some lukewarm water into it. Swirl the flask so that the entire clump of plants, along with jelly, loosens up and starts to swirl with the swirling action. Then carefully tip this plant and gel clump into lukewarm water, and then carefully separate jelly from roots/plant’s base. This not only makes it easier to clean off all the gel, but the roots also tend to suffer less damage this way.
Soak them in anti-fungus for 15 mins (Betadine mix with water will also work)
Remove plantlets from only one flask at a time and plant them quickly. It is best to plant in the morning before temperatures begin to climb significantly.
II. Humidity Trays
Tissue culture plants are grown in sealed containers where humidity is at 100%. When taken out of containers, these seedlings need to adapt slowly to “room” humidity.
The humidity trays are the easiest way to achieve this, and they are relatively inexpensive and fully reusable for any other gardening projects such as seed germination.
Carefully plant each plantlet in the seedling tray cell, firming it in gently and ensuring that the base of the plant is in good contact with the potting mix. Any existing roots should be buried, and more will form if these are damaged or absent. Transfer this tray to a polyhouse, hothouse, or humidity chamber, maintaining humidity at around 70%.
[If a humidity chamber is not available, a styrofoam box with two inches of wet sand at the bottom and a sheet of glass over the top will serve the purpose just as well. Cling wrap can also be used over the top with a few holes punched in it to allow air circulation. Sit the seedling tray on the wet sand.]
There are a lot of humidity-tray products. The one linked here is one we recommend for hobbyists as it is relatively compact and has everything you need all in one package (base tray, seedling/seed tray, and dome).
III. Potting Media
There are lots of choices for potting media but we highly suggest one that does not contain any pre-mixed fertilizer.
Use sterilized potting mix (if possible) with relatively low nutrient concentration. We use peat moss + perlite (50:50). Ensure the potting mix has been watered but is not too wet.
Avoid planting in a potting mix that is hot (>25°C). During the first few weeks of growth, it is beneficial (but not required) to maintain air temperatures within a range of 18-23°C.
After planting, you may spray the plants with a Mitre10 ( Moisture-Loc; Wilt Stop;…) solution for better results. This solution forms a protective film over the leaves and reduces rapid moisture loss from these baby plants, leading to faster hardening off. This product is also useful against frost-burn, sunburn, salt spray, windburn, and transplanting losses.
IV. Grow Lights
Seedlings must be kept away from direct sunlight or they will quickly wilt and die. In the early stages of growing a seedling, it is best to provide good indirect sunlight. A very easy setup is to simply put the seedlings under a grow light.
Keep the trays at 20-22°C in filtered light (the direct sun will turn the mini-greenhouse into a mini-pressure cooker). By late spring, through summer, and early autumn, shade screens must be used to reduce light levels. Up to 50% shade can be used during the peak of summer.
We recommend only fertilizing after the first month of planting. Not providing fertilizer right after planting will encourage root growth because the plant will try to seek nutrients by expanding its root system.
After the seedlings have been planted for a month, we recommend using a slow-release fertilizer.
As the plants develop, a mild liquid fertilizer can be sprayed to optimize plant growth rates. We use 20ml of 100% seaweed solution diluted in 10L of water every week or fortnight depending on the requirement.
VI. Mold/Bacteria Control
High humidity is always a catalyst for mold and bacteria growth. We use Captan Fungicide but that is a controlled chemical in many states so depending on where you live, it may not actually be available to you.
(Betadine, Mancozep also used)
We have attached a more “home use” organic fungicide/insecticide that we recommend to most hobbyist. See instructions for use when preparing to plant the seedlings. This product is also used after planting to control mold that may sometimes buildup in the trays