A scientist isolates chloroplasts from the leaves of a geranium plant after several hours of intense illumination. After rupturing the chloroplast membranes, she treats the insoluble internal carbohydrate residue with a solution containing triiodide ions (I3−\text{I}_3^-I3−), resulting in a characteristic deep blue-black complex. Name the specific storage polymer stored inside these organelles that is responsible for this color change.
