Genetic mosaics and the analysis of leaf development

Genetic mosaics with phenotypic markers can be used to study the developmen t of normal leaves. Mosaics synthesized between normal cells and cells poss essing developmental mutations can be used to determine whether or not a mu tation acts cell autonomously or if cell-to-cell interactions occur. This a rticle reviews the use of cytochimeras, plastid chimeras, radiation-induced chimeras, and graft chimeras to analyze leaf development in angiosperms an d to gain insight into the cell lineage, cell-to-cell communication, and th e control of morphology. New data are also presented. Leaves of plastid chi meras and graft chimeras were analyzed to determine the level of cell auton omy in different regions of the leaf blade. Evidence that small populations of leaf cells can act out developmental programs is presented. The relatio nship of these leaves to concepts such as developmental compartments, organ ismal theory, and pattern formation is discussed.