A Level Biology Practice Exam

Which layer of plant tissue is located between the endodermis and the phloem in roots?

1. Exodermis

2. Pericycle

3. Pith

4. Cortex

The correct answer is: Pericycle

The layer of plant tissue located between the endodermis and the phloem in roots is the pericycle. The pericycle is a critical layer of cells responsible for the formation of lateral roots and plays a role in secondary growth. It is a multicellular layer that can give rise to new tissues and is situated just inside the endodermis, making it uniquely positioned to interact with both the vascular tissues and the outer layers of the root. In contrast, the exodermis is typically found on the outer layer of the root's cortex, acting as a protective barrier. The pith, while important in other plant organs like stems, is generally absent or not prominently developed in roots. The cortex lies outside the endodermis and serves as a storage area and a site for gas exchange, but it is not located between the endodermis and phloem, thus distinguishing the pericycle as the correct answer in this context.