botanyone
Knowledge of tylose formation is mainly based on observations of extant species, and their developmental and functional significance are less well understood in fossil plants. Feng et al. study a permineralized stem of Shenoxylon mirabile, a Permian conifer more than 250 million years old collected from northern China, and find extensive development of tyloses from the innermost heartwood (metaxylem) tracheids to the outermost sapwood tracheids. They find no evidence of wounding or pathogenic infection and therefore suggest that tylose formation was a reaction to environmental stress, perhaps indicating that the tree was living during a period of extreme ecological conditions.
