Study on the influence of sediment oxidation-reduction potential on the growth of submerged aquatic plants Vallisneria natans and Potamogeton crispus under low-temperature conditions in spring

Potamogeton crispus and Vallisneria natans were used as the research objects to study the effects of different oxidation-reduction potential (ORP) conditions in sediment on the growth and physiology of submerged aquatic plants. The effects of different ORP on the plant height, fresh weight, and physiological and biochemical indexes of Potamogeton crispus and Vallisneria natans were analyzed by changing the ORP of sediment. The results indicated that a sediment ORP greater than −70 mV was conducive to the growth of both Vallisneria natans and Potamogeton crispus, whereas an ORP below −100 mV inhibited their growth. With the decrease of ORP, the growth rate of plant height and fresh weight of Vallisneria natans and Potamogeton crispus slowed down, accompanied by increased peroxidase (POD) activity and malondialdehyde (MDA) content, and decreased total chlorophyll content and soluble protein levels. Principal component analysis showed that the plant height, fresh weight, and total chlorophyll content of Vallisneria natans were significantly positively correlated with ORP, and POD activity and MDA content were significantly negatively correlated with ORP. The total chlorophyll content of Potamogeton crispus was significantly positively correlated with ORP, while POD activity, MDA content, and soluble protein content were significantly negatively correlated with ORP. With the increase of the anaerobic degree of sediment, the stress on Vallisneria natans and Potamogeton crispus also increased, and the tolerance of Vallisneria natans was worse than that of Potamogeton crispus. The research shows that in order to restore the growth of submerged plants, the oxidation-reduction environment of the sediment should be improved to provide a more suitable growth environment for submerged plants to promote the stable development of the lake ecosystem.