Which of these is the correct arrangement of tissues in herbaceous roots from the circumference to the center?

Answer Details

In a herbaceous (dicotyledonous) root, the tissues are arranged in concentric layers from the outside to the centre. Understanding this arrangement is essential for plant anatomy questions.

Moving inward from the surface:

1. Piliferous layer (epidermis): The outermost layer, bearing root hairs that absorb water and mineral salts from the soil.
2. Cortex: A broad region of parenchyma cells just beneath the epidermis. It stores food and allows lateral movement of water.
3. Endodermis: A single layer of cells at the inner boundary of the cortex (sometimes grouped with cortex in simplified descriptions).
4. Pericycle: A thin layer of meristematic cells just inside the endodermis. It gives rise to lateral roots.
5. Vascular tissue: The xylem and phloem, arranged in an alternating pattern within the stele.
6. Pith: The central core of parenchyma cells at the very centre of the root (in dicots, the pith may be small or absent, but in herbaceous roots it is typically present).

The correct sequence from circumference to centre is therefore: piliferous layer, cortex, pericycle, vascular tissue, and pith.

Exam tip: The pericycle always lies between the cortex (specifically the endodermis) and the vascular tissue. Any option that places vascular tissue before pericycle, or pith before vascular tissue, is incorrect.