What is the main process by which plants convert carbon dioxide and water into carbohydrates?

The process by which plants convert carbon dioxide and water into carbohydrates is known as photosynthesis. This fundamental biological process takes place primarily in the chloroplasts of plant cells and involves the absorption of sunlight, which provides the energy needed to drive the chemical reactions. During photosynthesis, plants utilize sunlight to convert carbon dioxide from the atmosphere and water from the soil into glucose, a simple sugar that can be used as an energy source for growth, cellular functions, and storage.

The overall reaction of photosynthesis can be summed up in the equation:

6 CO₂ + 6 H₂O + light energy → C₆H₁₂O₆ + 6 O₂

This illustrates how the raw materials (carbon dioxide and water) produce glucose (a carbohydrate) and oxygen as a byproduct.

Other processes mentioned in the question serve different purposes. For instance, respiration is the process in which plants (and animals) break down glucose to release energy, transpiration refers to the movement of water vapor from plant leaves into the atmosphere, and photodecomposition involves the breakdown of organic materials under light, which is not directly related to the synthesis of carbohydrates.