Effects of pH on the Submerged Macrophyte Hydrilla verticillata
Hydrilla verticillata (L.f.) Royle is widely distributed and protects the water environment mainly by serving as a potential heavy metal hyperaccumulator. Hydroponic experiments were performed to investigate the biochemical responses of the leaves and stems of H. verticillata at pH values of 5.5, 6.5, 7.5, 8.5, and 9.5 for 7, 14, and 21 days. The results showed that a weak alkaline environment (pH 8.5) promoted plant growth and that an acidic environment (pH 5.5, 6.5) adversely affected normal metabolism. The malondialdehyde content and three antioxidant enzyme activities changed in a similar pattern after the pH treatments: varying increases occurred following all pH treatments with the exception of pH 8.5. The activities of the three N metabolism enzymes briefly increased in an acidic environment and then sharply decreased compared to the control. The ROS-scavenging mechanisms and N metabolism mechanisms in H. verticillata worked together to respond to pH-induced effects. Based on the interplay between antioxidant enzymes and N metabolism enzymes, H. verticillata could defend against the toxicity induced by an acidic environment for approximately seven days and demonstrate stronger adaptability to the alkaline environment. Depending on the growth status and the synergistic effects of the enzymes, an optimum pH of 8.5 for H. verticillata was found in our experiment. Thus, these characteristics reveal a better understanding of this species so that it can be effectively controlled and better referenced for phytoremediation.
KeywordsHydrilla verticillata pH plant growth antioxidant system N metabolism
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