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All:
I've been looking all over the net and in books, but I'm still not clear on where to take the meristem explant from on the actual plant. I understand it's on the stem tip near the primordial leaves, but can someone point to a picture that actually shows this location or explain where this location can be (it seems it can be in a couple places on the plant).
Thanks,
Jon
Best I understand, it depends on the genus. Some you can do a root-tip meristem, where you simply remove the green tip from a root (and chop it up, and so forth and so on). With others, you need the actual plant growing tip, which is rather difficult to get to on monopodial growth habits, and requires at least wounding the plant, if not tearing it to bits, but is relatively easy and non-damaging with sympodial habits.Quote:
Originally Posted by jono
What genus are you working with, and what has your research turned up so far? I might not be able to help much, but perhaps somebody else will be able to.
for catts, it's the dormant eyes I believe. for monopodials like phals and vandas, it's the growing tip at the top. (which means sacrificing the plant to make the meristems, although the parent plant may possibly send up a keiki). meristemming is an involved process, and the quality/homogeneity of the progeny depend on both plant type and the skill of the meristemming technique.
here a a couple how-to articles. hope this helps.
http://www.easyorchids.co.uk/propaga...e_Culture.html
http://www.cedar-lodge.co.uk/page2.htm
http://www.aquabotanic.com/stiffaquatic.htm(how to do it in your kitchen)
Tissue culture
As its name suggest tissue culture is done by using plant tissue, mostly the minuscule center of a new growth. A lot of experiments have been made trying to do tissue culture out of leafs, roots,... but so far the most successful method uses tissue from a new growth.
The tissue is excised (cut), its outer layers are removed till the active center of developing cells, the meristem, is reached. Then this tiny mass of cells (it can be less than 1 millimeter in diameter) is cut into 20 or so parts, immersed into a flask with growing solution without agar, so the solution stays liquid. This media for this solution is usually called “multiplication” formula.
The flasks or tubes are placed on an agitator (an apparatus than either slowly rotates or tilts to the left then to the right. The constant movement of the agitator allows the lumps of cells to develop and increase in mass but prevents them from forming roots or leaves.
Once the lumps have sufficiently increased in size they are further cut into small lumps, placed into flasks or tubes and on the agitator. In this process the original 20 tiny masses may now be 400. At the next subdivision we may have 8,000.
This process continues until the desired number of lumps has been achieved.
Then the developed lumps are replated into flasks as is done for germinated seeds. From there on the process is the same as for seeds.
As in seed propagation all these operations require external disinfecting, and working in sterile conditions.
Plants developed from tissue culture, are called mericlones. They usually are very close in appearance (plant and flowers) to the plant from which the original tissue was taken and they are entitled to be recognized by the same variety name as the plant from which the original tissue was excised. So when you see a plant with a name like Cattleya Irene Finney “Z” it means this plant was propagated through tissue culture, using tissue from Cattleya Irene Finney ‘Z’.
Stem propagation.
In this technique a flower stem is used for propagation. If we propagated Phalaenopsis in this manner we would be looking for a flower stem with just the first flower open or with up to half the flowers open.
Flower buds nearer the base of the flower stem open first. Below them there will be a number of undeveloped buds, which we usually refer to as “nodes”.
The flower stem is removed from the plant and is externally decontaminated.
The stem is cut about 1 inch above and below the node, then dipped in decontamination solution for 15 to 20 minutes.
Then the protective sheath over the node is removed and about 1/8 of an inch is further removed from both ends of the stem (above and below the node).
The cutting is inserted in the media solution which is in a tube or jar or flask which was previously sterilized through autoclaving.
If the operation is successful we may get up to 4 plantlets per node.
Obviously this technique only produces a few plants from a flower stem of the original plant. We may get 10 to 15 stem propagated plants as opposed to the thousands we may get through tissue culture.
Because of the limited yield and the labor intensive procedure stem propagated plants tend to be much more expensive than plants propagated through seed or tissue culture.
On the other hand, unless some abhorrent mutation occurs, these plants will be exactly like the plant they were propagated from.
These plants too are entitled to be recognized by the same variety name as the original plant from which the original tissue was excised.
As with seed propagation and tissue culture all these operations must be conducted in a sterile environment.
Internode propagation
This technique is similar to the stem propagation but instead of using a flower stem as the start up point we use a growth. It is often used with Dendrobiums.
A growth is removed from the plant and is cut in between nodes. The edges are dipped in a fungicide and then either inserted or laid on sphagnum moss kept moist.
If the operation is successful we may get 1plantlet per node, but usually much less than that as many nodes will not develop a plantlet.
Still the technique does not require any sophisticated equipment, is inexpensive and can be done practically by anyone.
These plants too are entitled to be recognized by the same variety name as the original plant from which the growth was removed.
Divisions & back bulbs
Some orchids grow by developing new growth from the base of the plant. After several years they may have 5, 6, 10 or more growths. We may subdivide such plants to get two or three out of the original one.
Often the older growth or old pseudobulbs of these plants do not do anything but if we remove them and plant them separately they will generate new growth.
Again as for the previous methods where plants were propagated by using tissue, or the fower tem, plants resulting from divisions and backbulbs are also entitled to be recognized by the same variety name as the original plant from which the growth or back bulbs were removed. The resulting plants will be identical to the plant we divided or from which we removed the pseudobulb(s).
Keikis
Some orchids, mostly Dendrobiums, are notorious for producing keikis which is the Hawaiian word for “babies”.
Occasionally Phalaenopsis will also produce keikis. Some, usually species, do it because it is programmed into their genes, others do it when they are exposed to high temperatures while they are developing a flower stem.
Keikis will develop leaves first. Eventually they will develop roots. When roots have reached about an inch in length we can remove the keiki from the mother plant and plant it in its own container.
Keikis will be identical to the plant they were removed from and are also entitled to be recognized by the same variety name, if any, as the plant from which they originated.
Top cuts
Finally, some plants, mostly vandaceous orchids, tend to grow very tall. Heights of 4, 5, 6 feet or more are not unusual, making them difficult to handle. These also tend to develop new roots along their stem, in between leaves. These can be divided by
cutting off the top portion of the plant as long as this top portion has at least 2 pairs or roots attached to it.
The remaining (bottom) part of the plant will often respond to this attack by sending out new shoots from its base.
Top cuts are of course the same as the plant they were removed from and are also entitled to be recognized by the same variety name, if any, as the plant from which they originated.
(SOURCE:orchidsusa.com)
Wow, Matt. Excellent information there. Thanks for taking the time to post all of that!
Meristems are located wherever the plant grows from. You can use root tips, leaf tips, eyes, nodes etc. However, the quality of the meristem depends on where you take it. Root meristems are not as good as leaf meristems, you are likely to get much higher mutation rates. The more stable the tissue, such as node or leaf tip, the lower your mutation rates.Quote:
Originally Posted by jono
It may also interest you to know that what people call meristems etc, are not meristems whatsoever. They are only using meristematic cells for propagation. The meristem is much much smaller than the piece of tissue that is cultured.