Distinct pattern of zeatin distribution in the shoot apical meristem marks stress conditions in Posidonia oceanica (L.) Delile plants

In the present work, the immunocytochemical detection of zeatin was performed in the shoot and rhizome of Posidonia oceanica (L.) plants, growing in two sites subjected to different types of anthropic pressure. P. oceanica, the predominant seagrass of the Mediterranean basin, plays a pivotal role in marine ecosystems; it is considered an excellent bioindicator of sea disturbance. Due to a wide range of factors, mostly related to human activities, a significant and widespread decline of P. oceanica meadows is currently underway. Hence, there is much interest towards finding novel descriptors of impaired features in this seagrass, which could be used in monitoring projects. Our data resulted in a specific distribution pattern of zeatin in plant shoots in relation to environmental stress factors, while no significant differences were observed in rhizomes. These results are consistent with the role of cytokinins in shoot morphogenesis and growth. On the basis of cytokinin involvement in the light-dependent signaling cascade and stress response, the putative relationship with light availability is also discussed.