Immature Ovule Culture

Culturing of immature ovules is resorted to in cases where pollination is successful but for certain reason of incompatibility , the seeds do not develop beyond a certain stage. The procedure can succeed only if at least a few days have elapsed after fertilisation . Nimoto and Sagawa (1961) were the first to attempt this in orchids . According to them the seeds could be taken out for culturing only about 55 days after pollination . But Israel (1963) reports having taken seeds out of the ovaries seven days after pollination and cultured them to seedling stage.

There are some genera like Cypripedium and Paphiopedilum whose seeds are especially difficult to germinate. In such cases the seeds coat is said to contain certain substances which retard or even prevent the process of germination (Northern , 1970). Culturing of ovules before seed coat is developed fully will give a higher percentage of germination in such cases . The immature pod is sterilised , cut open with a sterile knife and the seeds scooped out and put in a vial containing distilled water. It is shaken well and the seeds sown to come in direct contact with the seeds. Other special techniques have also been suggested to tackle such hard to germinate seeds. Kano (1968) reported that immersing of seeds in sterilised water for 5 hours prior to flasking and sealing the flasks entirely quickened the process of germinate of the seeds of Cymbidium virescens and C. gyrokuchin . Similarly soaking of seeds of Cypripedium acaule (Which is very difficult to germinate under normal conditions) in a sterile nutrient solution for 15-45 days and putting them in unaerted flasks , is reported to hasten germination . Flasks should preferably be kept at 25 C and under diffuse light, in an incubator or in a green house under glass.