When plants photosynthesize, they convert carbon dioxide from the air and water from the soil into a carbohydrate, namely glucose. Carbohydrates are organic food for plants and all other living things. Animals, including humans, either eat plants directly or eat animals that have eaten plants. When provided with a source of nitrogen and sulphur, plants have the metabolic capability to modify and change carbohydrates into all the other types of organic molecules they require. This makes it possible for vegetarians to not only acquire carbohydrates but also amino acids from plants. The usual slimness of vegetarians testifies that most plants are not an abundant source of fat, and this fact can only make the vegetarian diet even more appealing.
Plant cell metabolism utilizes most of the same vitamins and minerals that humans require. Minerals are found in the soil in low concentrations, but plants are able to take them up and concentrate them. As the root system of a plant grows, it branches and branches again so that the roots are exposed to a tremendous amount of soil. Water enters the roots by diffusion, but active transport is needed to acquire some minerals and to concentrate minerals within the organs of a plant. A plant uses a great deal of ATP for active transport.
Once plants have taken up minerals, they are often incorporated into other molecules, including amino acids, phospholipids, and nucleotides.
Ground-level ozone in smog destroys leaves and roots. Acid rain, which causes minerals to be leached from the soil, can even cause the death of plants. Global warming may cause the extinction of many plant species. Global warming is due to the build-up of carbon dioxide in the atmosphere from the combustion of gasoline, coal, and oil. Carbon dioxide acts like the glass of a greenhouse-it allows the sun’s rays to pass through but traps the heat and doesn’t allow it to escape.
Soil erosion occurs when the wind blows and the rain washes away the top soil because farmers have ploughed the land in straight rows and/or left it without adequate cover. Soil erosion can be halted by the implementation of proven techniques, e.g. contour farming, drip irrigation, no-till farming, that might also halt desertification, the further degradation of the land to desert conditions.
Considering how dependent we are on plants, we must remember that plants as well as animals, including humans, are affected when the quality of the environment is reduced.