I decided to share my interest and expertise in the field of horticulture that I specialize in, which is plant tissue culture and micropropagation.
*Picture of some African Violet plantlets I started a few weeks ago*
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. Plant tissue culture is widely used to produce clones of a plant in a method known as micropropagation. The tissue culture starting material can be as small as a single plant cell, because plants exhibit totipotency, or the ability to regrow a completely new plant from a single somatic cell, but the most common explant material is leaf tissue or tissue from a meristematic region such as the apical meristem.
Micropropagation is the practice of rapidly multiplying stock plant material to produce a large number of progeny plants using tissue culture methods. Once a tissue culture has been established and plantlets start to form, you can then theoretically derive an exponential amount of new plant material from the starting material.
1.) Establishment - Micropropagation begins with the selection of plant material to be propagated. Clean stock materials that are free of viruses and fungi are important in the production of the healthiest plants. Once the plant material is chosen for culture, the collection of explant(s) begins and is dependent on the type of tissue to be used; including stem tips, anthers, petals, pollen and others plant tissues. The explant material is then surface sterilized, usually in multiple courses of bleach and alcohol washes and finally rinsed in sterilized water. This small portion of plant tissue, sometimes only a single cell, is placed on a growth medium, typically containing sucrose as an energy source and one or more plant growth regulators (plant hormones). Usually the medium is thickened with agar to create a gel which supports the explant during growth. The plant tissue grows and differentiates into new tissues depending on the medium. For example, media containing cytokinins are used to create branched shoots from plant buds.
*Some watermelon cultures I started with tissue from the seed embryo*
*Media contains a cytokinin 6-Benzylaminopurine to induce shoot formation*
2.) Multiplication - Multiplication is the taking of tissue samples produced during the first stage and increasing their number. Following the successful introduction and growth of plant tissue, the establishment stage is followed by multiplication. Through repeated cycles of this process, a single explant sample may be increased from one to hundreds or thousands of plants. Depending on the type of tissue grown, multiplication can involve different methods and media. If the plant material grown is callus tissue, it can be placed in a blender and cut into smaller pieces and recultured on the same type of culture medium to grow more callus tissue. If the tissue is grown as small plants called plantlets, hormones are often added that cause the plantlets to produce many small offshoots that can be removed and recultured.
*African violets started a few months ago in one jar, now many jars*
3.) Pre-Transplant / Hardening off - This stage involves treating the plantlets/shoots produced to encourage root growth and "hardening." It is performed in vitro, or in a sterile "test tube" environment.
"Hardening" refers to the preparation of the plants for a natural growth environment. Until this stage, the plantlets have been grown in "ideal" conditions, designed to encourage rapid growth. Due to lack of necessity, the plants are likely to be highly susceptible to disease and often do not have fully functional dermal coverings and will be inefficient in their use of water and energy. In vitro conditions are high in humidity and plants grown under these condition do not form a working cuticle and stomata that keep the plant from drying out, when taken out of culture the plantlets need time to adjust to more natural environmental conditions. Hardening typically involves slowly weaning the plantlets from a high-humidity, low light, warm environment to what would be considered a normal growth environment for the species in question. This is done by moving the plants to a location high in humidity.
4.) Transfer From Culture - In the final stage of plant micropropagation, the plantlets are removed from the plant media and transferred to soil, hydroponic, or (more commonly) soiless media for continued growth by conventional methods.
This stage is often combined with the "pretransplant" stage.
So, how do we apply this to our favorite plant, cannabis? Unfortunately there isn't anywhere yet in the US that the ability to mass multiply cannabis would be needed, because each cell culture could potentially be considered a cannabis plant on its own and the vast number of plant material that could be created would surpass the allowable plant limits under most MMJ laws. I could be wrong on this, please chime in if you have a more definite answer.
Edit (5/18/2013): The previous paragraph is no longer the case with the legalization of recreational marijuana use and sales in Washington and Colorado. I am only familiar with the particulars of the current Colorado laws and regulations, and it looks like a full fledged commercial cannabis tissue culture and micropropagation lab would be legal.
One possible application for this technique could be the storage of a large selection of different strains to be multiplied when needed and yet not taking up as much space as maintaining the same number of mother plants.
I'm planning a few experiments right now to test which media mix would be best for each stage of the micropropagation process with cannabis. So far the only reference I could find to give me a place to start was here:
This study was for the micropropagation of Hemp grade Cannabis Sativa, however, so from my experience with different varieties of watermelons, the concentrations of hormones will probably be very different for Recreational Cannabis, but the particular hormones stated TDZ and NAA will be a good place to start.
Well, wish me luck and let me know if any of you have questions pertaining to this exciting side of horticulture.
Edited by Berry, 18 May 2013 - 01:46 PM.