Plants and the Logic of Development

It seems likely that plants and animals have independently evolved multicellular development. Members of each kingdom are composed of different types of eukaryotic cells, implying that the two kingdoms diverged when their common eukaryotic ancestor was unicellular and that each lineage had a considerable unicellular history after they separated. This indicates that each kingdom separately evolved its mechanisms of cellular differentiation and cell-cell communication. This in turn raises a series of questions: do land plants and metazoans use the same fundamental mechanisms of development and perhaps even the same genes for similar processes, or has independent evolution of development meant the invention of completely different ways of doing things? Is there only one way to evolve a developmental system, or more than one? Is more than one type of multicellular development even possible?