Meristem culture

Culture of meristem tips were started first by Morel and co-workers in the nineteen fifties with the intention of obatining virus -free plants from those already infected . In 1960 he tried this methos in a virus infected Cymbidiuma and succeeded in ontaining a aplantling free of infection . Following this , Wimber (1963) ,Hamilton (1964) and Morel (1964) developed methods by which a single detached meristem could be cultured , divided into several bits and each bit subcultured . by repeating this several times over , an incredibly large number of plantings could be obtained from a single protocorn. in one year.

Meristems are dissected out with the help of a sharp razor-blade , the operation being carried out under a microscope. It should be 500 in length and about the same in diameter . These tiny bits of meristems are then sterilised with 2 % calcium hypochlorite solution and placed in a liquid nutrient medium in a flask under sterile conditions. The flask is then placed on a rotary shaker and rotated at a given speed. This is to prevent formation of any polarity to the developing meristem . Light equivalent to 200 foot candles and a temperature of 22 C are maintained throughout . Within a week the meristems will turn green . It starts developing several lumbs of tissue . At this stage the protocorn is taken out , washed and cut up into as many pieces as there are balls of tissue . Each bit is dipped in a sterilant and put in a tube containing fresh liquid medium and agitated . The procedure is repeated until as many plantlings as required are produced . The tiny balls of tissue are then transferred to normal nutrient agar medium and akept static as in seedling culture. Each ball of tissue , after reaching 4 mm in length differentiates into an individual plant.

The technique of propagation by meristem culture provided a great boost to the orchid industry . Rare plants of special qualities which could not be propagated by seeds due to genetic factors , could be multiplied easily and that too at a fantastic rate. This naturally brought down the prices of these orchids which were otherwise too expensive for most people to possess. Precious plants which fell victims to the incurable virus diseases also could be salvaged .

The only disadvantage with propagation by meristem culture is that removal of meristem causes temporary set-back in the growth of the mother plant. To avoid this ,parts of seeds due to genetic factors , could be multiplied easily and that too at a fantastic rate . This naturally brought down the prices of these orchids which were otherwise too expensive for most people to possess. Precious plants which fell victims to the incurable virus diseases also could be salvaged.

The only disadvantage with propagation by meristem culture is that removal of meristem causes temporary set-back in the growth of the mother plant. To avoid this , parts of the plant other than the apical meristem , have been tried in tissue culture experiments .Churchill, Arditti and Ball (1971) conducted experiments with leaf-tips and reported that the excised leaf-tips of Epidendrum and Laeliocattleya produced calli when put in liquid culture medium and roated . Upon being transferred to agar media these calli produced plantings .

One of the more recent development in vegetative multiplication of orchids is the use of cytokinis for promoting dormant buds to develop into young plants or 'Keikis '. This has been well described in an article by Brasch and kocsis (1980) from the McMaster University , Hamilton , Ontario , Canada . Experiments are in progress on several genera , but the greatest success so far has been achieved in Phalaenopsis , which has a mopodial habit. While the mericloning technique is wiedly used by large establishmets like commercial nurseries , for the amateur growing a few plants and desiring to increase them , the discovery of " Keiki grow " , and its availability are of great interest . Orchid " keiki Fix " formulated by N.F.Hass and marketted by H.G. Hees , 99 a kilin Ride, workingham , Berks , RG11 3 PD, U. K is reported to be equally effective on the dormant buds on Phalaenopsis inflorescence stalk .