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G14 dirk ventham's giant

  • #21
Well, there is no doubt that mutations happen naturaly, but one can double the chromosomes of a plant in tissue culture using a chemical called colchicine. Its used in orchids all the time to make the plants with the label 4N. N represents the halfploid number. Everything is normaly 2N. When they have double chromosomes they are called 4N. The chemical inhibits the cells from splitting during mitosis, but they still double thier chromosomes. Then the chemical is removed and they start deviding like normal only they now have double chromosomes. Most 4N orchids are larger then thier 2N parents. As with orchids when you start getting into hybred you can have two hybred look almost identical but made with 2 different species parents. Thats why its so hard to identify a NoID hybred orchid. Amature growers don't go try to find or use colchicine unless you have expreance. It has a MSDS sheet a mile long with some nasty side effects. Its also used to treat gout.
 
  • #22
I have read this before, is it true that some if not most 4N orchids are sterile?
Is this chemical used at the seed stage or during multiplication? If seed is made with one side 4N and the other 2N does the seed come out 2N? I do a little crossing of orchids and inquiring minds would like to know.
Sorry about srtraying off of the origonal post but wat the hay.
Thanks for any info.
Stephen D
 
  • #23
This talk of double chromosomes is related to gigantism according to a previous couple of posts. There is no true 'giant' VFT, just clones which have 5cm traps. This is no different from a person being 6' 2" tall.
 
  • #24
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  • #25
Sdeering I didnt say the 4N were sterile its the 3N ones that are. Ok you normaly have 2n chromosimes and when you split that during miosis you get N or the halfploid number. Sperm and egg cells have half the number of chromosomes. OK you have a teraploid (4N) and you make a sperm cell or egg cell with half of its chromosomes you get 2N chromosomes because it started with 4 strings, and when you half that you get 2 strings. IE 2N. So now you cross a 4N plant (pollin or egg having 2N) with a 2N(normal) plant (its egg or pollin having only N) when you add those together you get 3N. Its a lopped sided crhomosome count. Good thing we don't have to worry about plants being mentaly impared. Just an example Down syndrome in humans happens when this kind of thing occures in the 21'st chromosome. Downs syndrome is also called trisome 21. A mutation occurs during miosis and instead of splitting the 21rst crhomosome both strings of that one goes off to one side and when the egg is paired with a sperm the zygote has 3 chromosome 21's. The flasks are inoculated with the colchicineduring the mother flask stage of growing orchids. I have never done it nore seen it this is combining what I learned in anatomy and what I have read.
 
  • #26
Hey thanks for the info Josh. Its a little confusing but interesting none the less.
Lets see if i understand this. So if you have a double chromosone plant 4n and cross that with a normal plant 2N. This will yield all 3n, or will there be a mix of 2N and 3N in the seed. Also If you take a 4N and cross that with a 4N will the result be all 4N or a mix as well.
Stephen
 
  • #27
4N when crossed with an 2N will yeild a 3N plant because on the half chromosome thing.  There willbe variation but the chromosome count will be the same unless of mutation.  4N crossed with a 4N will yield a 4N again because each parent give half of its chromosome count.  Unless a mutaion accures, but thats not due to double chromosomes that just happens sometimes. When trying ti figure out things just remember that the parent gives half so in case of a 4N plant half is 2N and if you have another 4N plant that is giving 2N you ad the two halves togetehr and thats 4N again. In the case of 4N crossed with 2N then you have 2N from the 4N plant and N from the 2N plant and the yield when added together is 3N. Its devision then addition everytime. Unless you throgh a munkey wrench in the situation like the chemical.
 
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