Effects of cadmium on gametophyte growth and archegonia development in the endangered floating fern Ceratopteris pteridoides in China

Ceratopteris pteridoides is an endangered annual floating fern in China. This study tested the effect of cadmium on gametophyte growth and archegonia development of the aquatic fern C. pteridoides in culture. The results show that C. pteridoides spores germinated after being treated with different cadmium, but it was not significant compared with the reference group (45.63%). With the increase of cadmium, the rates of hermaphrodite gametophyte, the number of archegonia of C. pteridoides decreased, and archegonium differentiation was delayed gradually, indicating that cadmium caused adverse effects on sexual organ differentiation of C. pteridoides, further exacerbating the endangered status of this species in China. We suggest that it is necessary to pay more attention to protecting the primary habitats of C. pteridoides in China and reduce the impact of human activities from excessive aquaculture and industrial wastewater discharge on the water body in its living water body. KEY POLICY HIGHLIGHTS Ceratopteris pteridoides is an endangered aquatic fern, and listed in the second category of protected wild plants in China. With the increase of the concentration of Cd2+, the proportion of hermaphroditic gametophyte and the number of archegonium decreased gradually, indicating that cadmium caused adverse effects on sexual organ differentiation of C. pteridoides. We suggest that it is necessary to protect the primary habitat of the species, especially the protection of its living water body.