As seen in Figure , there are some white many crystals covering the roots of the plant. According to the elemental analysis tool, the white crystals were composed mostly of carbon and oxygen, which is expected in an aquatic plant as plants as plants are autotrophs. This means they produce their own food using the process of photosynthesis to transform water, sunlight, and carbon dioxide into oxygen. Some of the carbon is used for plant growth, and some of it is used in respiration, where the plant breaks down sugars to get energy . However, as seen in Figure , it is evident that nitrates were absorbed by the macrophytes as the elemental analysis chart shows a higher potassium concentration in the Pontederia crassipes root after being in a KNO₃ solution for 72 hours. The potassium cation remains in the root while the nitrate anion was absorbed.