What dense storage granules in plant cells are thought to contribute to gravitropism?

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Starch is a dense storage granule in plant cells that provides a source of energy during periods when photosynthesis is not possible. Starch is also thought to contribute to gravitropism because it is denser than the surrounding cytoplasm and is believed to sink to the bottom of cells under the influence of gravity, causing the cell to sense its orientation and respond accordingly. Cellulose is a structural polysaccharide that forms the cell wall and is not directly involved in gravitropism. Proteins and chlorophyll are also not directly involved in gravitropism.

What Dense Storage Granules in Plant Cells Are Thought to Contribute