Dissolved inorganic carbon (DIC) in water affects the growth of underwater plants. Different forms of DIC like CO2, HCO-3, and CO2-3 can either help or hinder the growth and photosynthesis of submerged macrophytes. The study looked at eight types of underwater plants and found that some species can use HCO-3 for growth and photosynthesis, while others need CO2-3. Some plants can adapt to a wide range of DIC conditions, while others are more sensitive. The ratio of HCO-3 to CO2-3 and the pH of the water are important factors that determine how well underwater plants can grow.