Developmental potentialities of leaf primordia of Osmunda cinnamomea. IV. Expression-potential of undetermined primordia separated by a barrier membrane from undetermined or determined primordia

Abstract

Undetermined P3 leaf primordia of the fern Osmunda cinnamomea were excised and grown in sterile culture, as pairs, with P12 or P13 primordia, primordia already irreversibly determined as leaves. Undetermined P3 primordia of a pair (P3 with P3 or P3 with P12) separated by an impervious barrier membrane (mica sheets) exhibit a tendency to develop as shoots rather than leaves. When the barrier membrane was a Millipore Filter, P3's growing with other P3's also exhibited the tendency to develop as shoots. By contrast, undetermined P3 primordia of a pair (P3 with P13) separated by a Millipore Filter barrier membrane exhibit the tendency to develop as leaves. These results would suggest that cell-to-cell contact is not a necessary adjunct to transmission of a leafness morphogen, and they present still further evidence in favor of a hypothesis that determination of a leaf primordium as a leaf may be under the control of more than one control center, and that one such control center is associated with certain of the older leaf primordia of a sibling series.