Transdetermination of plant cells.

Tissues derived from the leaf lamina of Nicotiana tabacum L. cv. Havana 425 plants require cytokinin for continuous proliferation in culture, whereas tissues derived from the cortex of the stem are cytokinin autotrophic. Both phenotypes persist when the two types of cells are cloned, indicating that leaf- and cortex-derived cells are determined to express different cytokinin requirements in culture. We showed that cultures derived from leaf and cortex tissues of plants regenerated from cloned leaf and cortex cells exhibit the cytokinin requirement of comparable tissues of seed-grown plants. This provides direct evidence that plant cells can undergo transdetermination and that this process has an epigenetic basis.