Abstract

Although land plants sustain life on earth, and their productivity is limited by architecture, we have little understanding of how changes in architecture came about during evolution. In the majority of extant land plants, the vascular plants, the diploid sporophyte generation is dominant and architectural diversity is generated by differences in branch and leaf initiation patterns. Despite this variation, all vascular plants have a capacity for indeterminate growth from meristems located at the tips of their growing branches. An evolutionary starting point for sporophyte architecture is given by the bryophytes that are basal in plant phylogenies. In mosses, the main group of bryophytes, the sporophyte has a determinate body plan: a single stem that terminates in the formation of a reproductive structure, the sporangium. By using the moss Physcomitrella patens as a model and a combination of approaches, I aim to determine whether there are regulatory mechanisms of sporophyte meristem function shared across the land plants and to identify pathways by which indeterminate growth may have arisen.