Nitrite in the bloodstream converts hemoglobin into methemoglobin which is incapable of carrying oxygen. The methemoglobin discolors the blood, turning it a brownish color. This same color can be seen in the eyes of animals suffering from nitrite poisoning. As the case becomes more severe, animals begin to tremor, muscles twitch and they lack coordination. Eventually the animal may die if not treated intravenously with a methylene blue solution by a veterinarian.
Nitrates accumulate primarily in the stems of plants.
The leaves do not have as high of a concentration of nitrates. During periods of dry weather, the nitrate levels of plants will increase after a rain. The moisture allows the nitrate in the soil to be absorbed by the plant. Some moisture needs to be present for plant uptake of soil nitrates. Frost and hail can also increase plant nitrate content.