Morpho-structural and histochemical features of Plantago fengdouensis (Plantaginaceae) that reflect adaptations to an amphibious environment

The perennial Plantago fengdouensis (Plantaginaceae) is an endangered amphibious plant native to the Three Gorge Reservoir Area, along the Yangtze River, China. Using brightfield and epifluorescence microscopy, we investigated the anatomical and histochemical features that allow this species to tolerate both submerged and terrestrial environments. The adventitious roots and rosette-like stems of P. fengdouensis had an endodermis inside the cortex, a uniseriate exodermis with Casparian bands and suberin lamellae, and phellem in the secondary structure; the cortex persisted to the root base. Dilated cells were found in the endodermis and inner cortex of the roots. The endodermis and sclerenchyma layer are present as a continuum from the roots to leaves, shoots are covered by cuticle, also. Air spaces were present in the roots and shoots. These anatomical and histochemical features may reflect adaptations that permit P. fengdouensis to thrive in the riparian zone of the Three Gorges, China.