Answer:
Plants primarily grow through a process called photosynthesis, which is a chemical reaction that converts light energy into chemical energy stored in glucose molecules. During photosynthesis, plants use carbon dioxide from the air and water from the soil to produce glucose and release oxygen. This process occurs in the chloroplasts of plant cells and is facilitated by a complex set of chemical reactions involving enzymes and pigments.
In addition to photosynthesis, plants also acquire nutrients from the soil through their roots. These nutrients are used to build molecules such as proteins and nucleic acids, which are essential for growth and development. However, the majority of the plant's mass comes from the carbon dioxide that it absorbs from the air during photosynthesis.
Therefore, the additional matter in a growing plant mainly comes from the carbon dioxide that it captures from the air through photosynthesis. While nutrients from the soil are important for plant growth, they contribute relatively little to the overall mass of the plant.
To summarize, plants grow through the process of photosynthesis, which converts light energy into chemical energy stored in glucose molecules. The primary source of new plant matter is carbon dioxide from the air, which is incorporated into glucose during photosynthesis. While nutrients from the soil are important for plant growth, they are not the primary source of additional matter in a growing plant.