The Maturation of Underdeveloped Embryos

 

A few species of woody plants produce seeds which,at the time of dispersal, do not have a mature embryo. This will therefore require this immature embryo to be provided with the necessary conditions to develop and mature to a condition at which the various processes leading to germination can proceed.

 

The immaturity of an embryo, in a seed at the time that it is dispersed, may vary from an amorphous aggregation of cells through stages of morphological differentiation to the final physiological maturation. These stages of development lead to the production of the mature embryo which is capable of processing into the germination or pregermination phase which ensues.

 

Whatever the stage of maturity of the embryo - it is necessary to treat the seed to bring the embryo to full maturity in order to proceed.

 

The first requirement will be to imbibe the seed and this may require any impermeable seed coat condition to be eliminated as a first step. Once this has been achieved the seed should be imbibed with a warm water soak – for about twelve hours - so that the seed contents are reconstituted with the minimum of detriment to the tissues.

 

Once this has been achieved it will be necessary to store the seed over a requisite period of time in order to allow the embryo to reach full maturity. This length of time will reflect the degree of immaturity of the embryo and the temperature at which the storage is maintained.

 

The storage environment must of necessity provide conditions which will allow the maintenance of the viability of the embryo, hence the water status of the seed will have to be maintained and a suitable atmosphere provided. This is usually achieved by using compatible materials (such as are described for chilling the seed in dormancy breaking) and packaging and labelling in the same way.

 

A storage temperature in the range of 20-30˚C will normally achieve an effective result - higher temperatures may lead to the food storage materials (especially if they consist of fats, waxes and oils) in the seed becoming rancid and lower temperatures will necessarily cause a much slower response – with the possibility that there will be some losses in the sample by an attenuated ageing process.