Final answer:
Most plants function within a photosynthetic autotrophic system, where they use sunlight, carbon dioxide, and water to produce their own food via photosynthesis, thereby increasing their mass.
Step-by-step explanation:
The kind of system within which most plants function is known as a photosynthetic autotrophic system. Plants, unlike animals, have the ability to make their own food through the process of photosynthesis, which requires sunlight as an energy source. They convert carbon dioxide (CO₂) and water (H₂O) into sugars and release oxygen as a byproduct. Notably, plants can increase their mass beyond the inputs of water and carbon dioxide because they incorporate carbon from CO₂ into their tissues, which adds to their dry weight.
Plants that do not have access to sufficient sunlight or water will struggle to perform photosynthesis effectively. Consequently, their growth will be stunted, negatively affecting not only their survival but also that of the organisms that depend on them for food. Also, as photosynthesis takes place primarily in the leaves of plants, the presence of structures such as stomata allows for the regulation of gas exchange and the necessary intake of carbon dioxide. It's through these intricate systems that plants function and contribute to their own growth and the ecosystem at large.