Holocrine Secretion and Kino Flow in Angiosperms: Their Role and Physiological Advantages in Plant Defence Mechanisms Paulo Cabrita Dr. Paulo Cabrita Soderstr. 39, 64287 Darmstadt, Germany ORCID ID: 0000-0002-2620-3573 Corresponding author E-mail:
[email protected] Current Address: Weserstr.36, 37081 Göttingen, Germany Telephone: +49 551 48942338 Acknowledgements This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors. The author would like to thank to two anonymous reviewers for the careful reading and the very helpful suggestions and criticism of this manuscript. This is a post-peer-review, pre-copyedit version of an article published in Trees. The final authenticated version is available online at: https://doi.org/10.1007/s00468-020-01990-z 1 Abstract Kino is a plant exudate, rich in polyphenols, produced by several angiosperms in reaction to injury of the cambium. It flows out of kino veins, which compose an anatomically distinct continuous system of tangentially anastomosing canals produced by the cambium upon damage, encircling plant stems and branches. Kino is loaded into the vein lumen by autolysis of a cambiform epithelium lined by suberized cells that separate kino veins from the surrounding axial parenchyma. A model describing kino flow is presented to investigate how vein distribution and structure, as well as the loading, solidification, and viscosity of kino affect flow. Considering vein anatomy, viscosity, and a time-dependent loading of kino, the unsteady Stokes equation was applied. Qualitatively, kino flow is similar to resin flow observed on conifers. There is an increase in flow towards the vein open end, with both pressure and flow depending on the vein dimensions, properties, and loading of kino.