Influence of previous drought exposure on the 3D microstructure of the cambium and developing xylem in Eucalyptus clones: An X-ray CT investigation

Abstract

Summary In plant biology research, X-ray computed tomography (CT) has been demonstrated to be useful for studying the complex tissues of trees qualitatively and quantitatively. The cambium plays a very important role in plant growth and development. However, this tissue is relatively poorly studied due to its complex nature and its localization between layers of xylem and phloem cells. Antecedent environmental conditions may have a substantial impact on plant responses to drought and recovery dynamics. Therefore, this study aimed to investigate the impact of previous drought exposure on the 3D microstructure of two commercial Eucalyptus clones by monitoring the development of the cambium, in the same plant and same area of cambial tissue, during a 4-week trial consisting of well-watered, mild drought, severe drought, and rewatering phases. To track microstructural changes, the plants were imaged weekly with non-destructive X-ray micro-computed tomography (μCT). On the last day of the experiment, X-ray nano-CT was also performed. Our results indicate that trees subjected to earlier well-watered conditions were more affected by the severe drought, compared to those previously exposed to mild drought conditions. Thus, previous exposure to water deficit may provide the benefit of increased drought tolerance during future water deficit. Previous mild drought exposure can facilitate morphological adjustments, which potentially enhances drought tolerance during subsequent drought events.