DENDROLOGY

Detailed explanation-1: -The appearance of blue-black color indicates the presence of the starch in the sample, i.e., a positive iodine test (Figure 3). The brown color or no change in the color of the sample indicates the absence of the starch in the given sample, i.e., a negative iodine test (Figure 3).

Detailed explanation-2: -Iodine does not react with other carbohydrates that are not coiled, and remains yellowish brown. Therefore, a bluish black color is a positive test for starch, and a yellowish brown color (i.e., no color change) is a negative test for starch.

Detailed explanation-3: -Iodine Solution is used to test the presence of starch.