The study of plant development in recent years has often been concerned
with the effects of the environment and the possible involvement of
growth substances. The prevalent belief that plant growth substances are
crucial to plant development has tended to obscure rather than to
clarify the underlying cellular mechanisms of development. The aim in
this book is to try to focus on what is currently known, and what needs
to be known, in order to explain plant development in terms that allow
further experimentation at the cellular and molecular levels. We need to
know where and at what level in the cell or organ the critical processes
controlling development occur. Then, we will be better able to under-
stand how development is controlled by the genes, whether directly by
the continual production of new gene transcripts or more indirectly by
the genes merely defining self-regulating systems that then function
autonomously. This book is not a survey of the whole of plant
development but is meant to concentrate on the possible component
cellular and molecular processes involved. Consequently, a basic
knowledge of plant structure is assumed. The facts of plant
morphogenesis can be obtained from the books listed in the General
Reading section at the end of Chapter 1. Although references are not
cited specifically in the text, the key references for each section are
denoted by superscript numbers and listed in the Notes section at the
end of each chapter.