Development of anatomical structure of roots of Phragmites australis

Abstract

Summary Focusing on characters related to its survival in flooded soils, the anatomy and differentiation of roots of Phragmites australis is reported here. Roots were examined by anatomical methods and permeability tests using periodate‐, Fe2+‐ and berberine‐based apoplastic tracers. Root development was characterized by the differentiation of a multiseriate exodermis with suberin lamellae and Casparian bands that formed close to the root tip. Impregnation of the exodermis with lignin and/or suberin appeared closer to the apex than in the endodermis, which is not commonly observed in other plant species. The early developed exodermis proved to be an effective barrier restricting the passive apoplastic penetration of solutes from the rooting medium into the root tissues. Relationships between exodermis, endodermis, aerenchyma and lateral root primordia development were also recorded. It is concluded that early differentiation of the exodermis was advantageous in flooded substrates. Only a limited proportion of tissue without this apoplastic barrier might be crucial to reduce radial oxygen loss to the sediment and restrain the action of unfavourable factors, such as phytotoxins, in a flooded sediment.