The diagram shows a leaf on a plant.

Which characteristic of life is represented by this diagram?

The given diagram represents a vital phenomenon i.e., Photosynthesis. Photosynthesis is a mode of autotrophic nutrition in plants. It is essential to all life on earth; both plants and animals depend on it. It is the only biological process that can capture energy that originates from sunlight and convert it into a chemical compound (glucose) that every organism uses to power its daily functions.
Photosynthesis generally takes place in the leaves of plants. It is a multi-step process that requires sunlight, carbon dioxide ($C{O}_2$, found in the air), and water ($H_{2}O$, from the soil). After the process is complete, the plant releases oxygen into the air ($O_2$, essential for many living organisms) and produces the simple carbohydrate molecule of glucose, which can be used as an energy source by the plant, converted to starch and stored for a later energy source, or converted into other organic molecules such as fats, proteins and vitamins.