Tools to understand hypoxia responses in plant tissues.

Our understanding of how low oxygen (O2) conditions arise in plant tissues and how they shape specific responses has seen major advancement in recent years. Important drivers have been (1) the discovery of the molecular machinery that underpins plant O2 sensing; and (2) a growing set of dedicated tools to define experimental conditions and assess plant responses with increasing accuracy and resolution. While some of those tools, such as the Clark-type O2 electrode, were established decades ago, recent customization has set entirely new standards and enabled novel research avenues in plant hypoxia research. Other tools, such as optical hypoxia reporters and O2 biosensor systems, have been introduced more recently. Yet, their adoption into plant hypoxia research has started to generate novel insight into hypoxia physiology at the tissue and cellular levels. The aim of this update is to provide an overview of the currently available and emerging tools for O2 hypoxia measurements in plants, with an emphasis on high-resolution analyses in living plant tissues and cells. Furthermore, it offers directions for future development and deployment of tools to aid progress with the most pressing questions in plant hypoxia research.