The current growing interest of molecular biologists in plant hormone research is undoubtedly the most promising development of recent times. Many papers were presented during the 14th International Conference on Plant Growth Substances illustrating the impact of this new approach on our understanding of hormone-controlled processes. The specific character is the integrated study of plant growth regulation at all levels ranging from single molecules to the entire plant and its functioning in the environment. Hormones play an essential role in the regulation, but not an exclusive one. Other compounds and factors, such as Ca2+, for instance are often of equal relevance, because they may take part in the signal transduction pathway. Moreover, regulation of the regulator by non-hormonal factors is an essential part of any control mechanism. The present volume reflects the change in interest from plant growth substances to plant growth regulation.