Final answer:
Corn plants gain most of their mass from water absorbed through the soil and carbon dioxide from the air, which are converted into organic compounds through photosynthesis. Minerals from the soil also contribute to growth but to a lesser extent.
Step-by-step explanation:
The mass of corn plants at the end of their growth period, which is 6 tons per acre, is primarily derived from water from the soil and carbon dioxide from the air . This significant mass gain is attributable to the process of photosynthesis, in which plants absorb water through their roots and carbon dioxide through their leaves. Using sunlight as an energy source, they convert these substances into organic compounds such as sugars, which contribute to the plant’s mass. While minerals and nutrients from the soil are also essential for plant growth, they are required in much smaller amounts compared to water and carbon dioxide. Essentially, the dry mass of plants is largely made up of carbon, a critical element that plants obtain from atmospheric CO₂, thus incorporating the carbon into their structure and significantly contributing to their overall mass.