Effects of Developing Leaves on Stelar Pattern Development in the Shoot Apex of Matteuccia struthiopteris

A developmental study of the normal shoot apex of Matteuccia struthiopteris suggested that patterned stelar differentiation is initiated immediately beneath the single layer of promeristem and occurs prior to the initiation of the youngest leaf primordium. A developmental study in which all leaf primordia were suppressed, with or without lateral isolation of the terminal meristem by vertical incisions, has confirmed this interpretation of stelar differentiation. Experimentally-induced changes in the tissue immediately below the promeristem were reflected in the resulting mature structure of the stele. Failure of leaf gap initials to differentiate, if all leaf primordia were suppressed at the incipient stage, resulted in a mature stele without leaf gaps. Similarly the disappearance of pith mother cells after several weeks of leaf removal was associated with the formation of a stele without pith. Leaf influence was further assessed by allowing one primordium to develop while all others were suppressed. The developing leaf had a small promoting effect on cauline vascular tissue differentiation but its major impact on the expansion of the parenchymatous tissues of the stele. Characteristic protoxylem and protophloem failed to differentiate when all leaves were suppressed and, when leaf was allowed to develop, formed only in relation to the leaf.Copyright 1995, 1999 Academic Press