What is the function of starch in plants?

Starch in plants serves as a store of energy and as a source of carbon for photosynthesis.

Starch is a complex carbohydrate that is produced by plants as a way to store energy. It is primarily made up of glucose units that are linked together in a way that makes it ideal for storage. This is because the glucose units in starch are packed closely together, making it a very dense form of energy. When the plant needs energy, it can break down the starch into glucose, which can then be used in cellular respiration to produce ATP, the energy currency of the cell.

In addition to being a store of energy, starch also serves as a source of carbon for photosynthesis. During the day, plants take in carbon dioxide from the atmosphere and use it, along with sunlight and water, to produce glucose through the process of photosynthesis. Some of this glucose is used immediately for energy, but the excess is converted into starch and stored in the plant's cells. Then, during the night when photosynthesis cannot occur, the plant can break down the stored starch back into glucose and use it to continue the process of photosynthesis. This allows the plant to maintain a constant supply of carbon for photosynthesis, even when it is not able to take in carbon dioxide from the atmosphere.

Starch is stored in various parts of the plant, including the roots, stems, and leaves. In some plants, such as potatoes and rice, a large amount of starch is stored in the tubers or seeds, which is why these parts of the plant are often used as food sources by humans and other animals. The ability to store energy and carbon in the form of starch is a key adaptation that has allowed plants to survive and thrive in a wide range of environments.

IB Biology Tutor Summary: Starch in plants acts as an energy reserve and a carbon source for photosynthesis. Produced mainly from glucose, starch is stored densely, enabling efficient energy storage. It's used by plants during photosynthesis to create glucose, which is stored as starch for use when photosynthesis isn't possible. This adaptation helps plants manage energy and thrive in diverse environments.