Plants capable of performing photosynthesis belong to a specific type of organism, known as autotrophs. Autotrophs are able to produce their own food using energy from the sun, carbon dioxide, and water through the process of photosynthesis.

Let`s analyze the other options to understand why they are not the correct choices:

1. Heterotrophs: Heterotrophs are organisms that cannot produce their own food and rely on consuming other organisms for energy. Since plants that perform photosynthesis are able to produce their own food, they are not categorised as heterotrophs.

2. Saprotrophs: Saprotrophs are organisms that obtain nutrients by decomposing dead organic matter. They do not undergo photosynthesis, so plants capable of photosynthesis are not saprotrophs.

4. Chemoheterotrophs: Chemoheterotrophs are organisms that obtain energy by breaking down chemical compounds obtained from other organisms. Since plants capable of photosynthesis obtain energy from the sun, they are not chemoheterotrophs.

In conclusion, the correct answer is option 3, autotrophs, as plants capable of photosynthesis are able to produce their own food.