What layer of meristematic tissue lies under the endodermis and can form cork cambium or secondary roots?

The correct choice is the pericycle, which is a layer of meristematic tissue located just inside the endodermis of plant roots. The pericycle plays a critical role in the growth and development of roots. It is capable of forming lateral roots, which emerge from this layer and contribute to the overall structure and function of the root system. Additionally, the pericycle can differentiate into cork cambium, which is involved in the formation of secondary protective tissues in plants, enhancing their ability to withstand environmental stressors.

In contrast, the cortex is primarily involved in storage and transport but does not have the same regenerative capabilities as the pericycle. Meanwhile, the meristematic region is a broad term that refers to actively dividing cells found at various locations in plants, but it doesn't specifically designate the layer under the endodermis. The vascular cambium is also a meristematic tissue, but it is found between the xylem and phloem in stems and roots, playing a different role in secondary growth. Thus, the pericycle is uniquely suited to fulfill the functions described in the question.