Colchicine treatment to create Polyploid's posted by Member Coralman

coralman;3322881 said:

Colchicine treatment is done in one of the following ways:

a. Seed treatment:

The dry or soaked seeds are soaked in aqueous solution of colchicine of different strength in shallow container to facilitate aeration (generally, aqueous solutions of 0.25 to 0.5 per cent concentrations are used). Colchicine treatment is given for a definite period which is different for different seeds.

After the seeds are soaked in colchicine solution for desired period, they are washed thoroughly in water and then they are sown. Treatment of dry seeds gives better result than soaked seeds in some cases.

b. Seedling treatment:

Seedlings may be treated in young stage. During treatment, the shoot tips are dipped in 0.2% colchicine solution and root tips are covered with cotton soaked in water and the treatment may be given from 3 to 24 hours and in some cases the treatment should be repeated on 2nd and 3rd day also.

c. Treatment of growing buds of shoot:

In some cases growing points are treated with 0.1 to 0.5% solution of colchicine which is applied by brush or with a dropper. Sometimes cotton wool soaked in the aqueous solution of colchicine is applied over the growing point of plant.

The treatment is repeated once or twice daily for a few days. Alternatively, 0.2 to 0.5% colchicine solution is mixed with lanoline paste and is smeared on the shoot apex. This treatment may be repeated 2-3 times daily for a week.

d. In woody plants, 1.0% colchicine solution may be applied over the growing bud. For proper penetration of colchicine, the solution is applied 2-3 times a day for a week.

At any given time only a small proportion of cells would be in mitotic phase, hence repeated treatment should be given at brief intervals so as to double the chromosome number in good number of cells. There may be a competition between polyploid cells and unaffected diploid cells and some-times diploid cells may compete over the polyploid cells and diploid shoots may arise from the treated growing apex.

Effect of Colchicine:

When colchicine is applied some irregularities occur in the mitotic division. It has no effect on doubling of chromosomes which proceeds in normal fashion. This chemical is a spindle poison and it simply checks the anaphasic movement of chromosomes to the two poles and consequently mitosis fails to complete.

The doubled chromosomes become bounded by a nuclear membrane, thus a restitution nucleus with double chromosome number is formed.

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