Abstract:

Eremochloa ophiuroides and Hemarthria altissima are two wetland plants distributed in the Jianghan Plain area. These two species can survive in both terrestrial and wetland environments， and are able to adapt to seasonal floods in the Jianghan Plain. The selection of wetland plants and flooding-tolerant plants plays an important role in vegetation restoration in the various wetlands and drawdown zone in the middle reaches of the Yangtze River. To explore the mechanisms of water resistance reflected by the differences in anatomy and in structures related to environmental adaptability （e.g.， the aerenchyma and apoplastic barrier） between E. ophiuroides and H. altissima， we studied the anatomical and histological features of the roots and stems of these two species. To explore aspects of anatomy， sections of various plant parts were prepared， subjected to histochemical staining， and observed and photographed under a microscope. The results indicate that： 1） E. ophiuroides and H. altissima have anatomical structural characteristics that allow them to adapt to wetland environments and are typical wetland plants. These structural features include aerenchyma （stem air cavity and root schizo-lysogenic aerenchyma） and apoplastic barriers （endodermis， exodermis， suberization tissue， and cuticles）. The roots of both E. ophiuroides and H. altissima have an endodermis and exodermis， as well as suberized and lignified secondary walls. 2） The stem of H. altissima has a suberized and lignified peripheral mechanical ring and vascular bundle sheath， as well as a pith cavity. The stem of E. ophiuroides has a peripheral mechanical ring that is lignified but not suberized， a sclerenchyma ring and vascular bundle sheath cells， and a pith cavity and cortical aerenchyma. The stolons and rhizomes of H. altissima have a continuous suberized sclerenchyma ring， peripheral mechanical ring， and a vascular bundle sheath. The stolons of E. ophiuroides have a discontinuous lignified （but not suberized） peripheral mechanical ring. These findings indicate that H. altissima is better adapted to a submerged environment than is E. ophiuroides.

Key words: wetland plants, Eremochloa ophiuroides, Hemarthria altissima, anatomical structure, aerenchyma, apoplastic barriers