Atactostele is found in A. Dicot stem B. Monocot stemC. Dicot rootD. Monocot root

Atactostele is a type of vascular tissue arrangement found in certain plant stems. It is characteristic of ferns and is typically associated with primitive vascular systems.

Among the options provided, neither dicot stems nor monocot stems typically exhibit atactostele. However, some ferns, which are neither dicots nor monocots, can display this vascular tissue arrangement. So, the correct answer would be neither A nor B.

As for the options C and D, dicot roots usually exhibit a eustele or sometimes a plectostele, while monocot roots often have a modified eustele. Atactostele is not typical in either dicot or monocot roots.

Therefore, the correct answer would be none of the options provided: Atactostele is not found in dicot stems, monocot stems, dicot roots, or monocot roots.