Microinjection - Another possible delivery system might involve the direct injection of foreign DNA into plant cells using minute needles.

Microinjection of DNA into the nuclei of isolated protoplasts could be an efficient means of gene transfer. One good example is alfalfa.

As a technique, microinjection has the following merits:

(1) fairly high transformation efficiencies,

(2) minimal somaclonal variation because of avoidance of the cell culture phase following egg cell injection, and

Materials injected into the inflorescence can penetrate the developing germ cells.

For example, injection of the chemicals caffeine and colchicine penetrate the cells and produce developmental abnormalities in them.

To test whether DNA would also penetrate the cells, de la Pena (1987) injected rye inflorescences with DNA plasmids consisting primarily of a gene coding for resistance to the antibiotic kanamycin.

The seeds eventually produced were then screened for kanamycin resistance by germinating them in the presence of the antibiotic.