Wetlands are particularly sensitive to hydrological changes, such as the reduction in water supply during extensive droughts. In response to a reduction of water levels, many aquatic plants can become amphibious producing morphologically, structurally and physiologically different emergent growth forms. 

Potamogeton wrightii Morong is a heterophyllous plant, which grows primarily in freshwater and sometimes on land by producing terrestrial shoots. During summer, plants of P. wrightii growing in shallow water at lake margins often become emersed and produce a new set of terrestrial leaves in the aerial environment and grow well as a land plant for a few weeks.    

Researchers from Wuhan Botanical Garden comprehensively investigated morphological structure, physiological functions and molecular regulation in P. wrightii to reveal the underlying adaptive mechanism of photosynthetic metabolism to aquatic and terrestrial environments.    

Results showed that in terrestrial habitats, the aerial P. wrightii leaves were thicker with larger amounts of cutin and wax, developed stomata, greater tolerance to strong light, and a greater photochemical efficiency. In aquatic environment, the submerged leaves had a greater ability to use HCO_3^ˉ and to synthesize photosynthetic pigments. The transcriptome research revealed that P. wrightii adapted to aquatic and terrestrial environments by regulating leaf morphyology and anatomical structure and adjusting photosystems through the up/down-regulation of genes related to cutin and wax biosynthesis, photosystem I (PSI) and PSII, as well as outer light-harvesting chlorophyll protein complexes (LHCs).    

This study provides new insights on the capacity of aquatic plants to survive fluctuating water level, which could be attributed to their genotypes that resulted from their evolution from land plants and their phenotypic plasticity.   

Research was funded by the Strategic Priority Research Program of the Chinese Academy of Sciences and the National Natural Science Foundation of China. The results have been published in Environmental and Experimental Botany entitled “Biological adaptive mechanisms displayed by a freshwater plant to live in aquatic and terrestrial environments”.  

Adaptive mechanism of Potamogeton wrightii for differential morphology and photosynthesis in aquatic and terrestrial environments, respectively (Image by WBG)