Diaphragms and Aerenchyma in Scirpus Validus

After the short‐lived apical meristem ceases activity, a basal intercalary meristem produces all new tissues in the aerial internode of Scirpus validus Vahl. These include extensions of the original vascular system and of the original partitioning walls as well as new vascular bundles and new walls which are produced in a predictable pattern. Diaphragms begin to differentiate well within the intercalary meristem. At first their cells are indistinguishable from those that will become the aerenchyma, but they undergo segmentation and form packets of daughter cells. Such continued mitotic activity allows the diaphragms to expand with the increasing girth of the stem above the intercalary meristem. Aerenchyma cells between the diaphragms become stellate by being stretched as the cells of the vertical partitions divide and enlarge in and above the intercalary meristem.