The carbohydrate used as storage molecule in plants is

The correct option is Starch.

Carbohydrates serve as crucial energy sources and structural components in living organisms. Plants and animals have evolved different molecules to store excess glucose for future energy needs.

Why Starch is the storage molecule in plants:
During photosynthesis, plants produce glucose, which has the chemical formula:
$C_6{H}_{12}{O}_6$
Since glucose is highly soluble in water and chemically active, storing it directly as free glucose would disrupt the osmotic balance of plant cells. To prevent this, plants convert excess glucose into starch. Starch is a large, insoluble polysaccharide made of glucose monomers. Being insoluble, starch does not affect the osmotic potential of the cells, making it an ideal energy reserve stored in chloroplasts and specialized organs like tubers, roots, and seeds.

Understanding the other options:
1. Glycogen: This is the primary storage polysaccharide in animals and fungi, often referred to as "animal starch."
2. Cellulose: Although it is a plant polysaccharide, cellulose is a structural component of plant cell walls rather than a storage molecule.
3. Glucose: This is the simple sugar used directly for cellular respiration and energy production, but it is not stored long-term in this form due to its osmotic activity.