Lateral root primordia develop from specific cells within the root structure, playing a key role in expanding a plant’s root system for better nutrient and water uptake. The correct answer to this MCQ is the pericycle, which acts as the primary site for initiating these structures.

Correct Answer

(1) Pericycle initiates lateral root primordia through asymmetric cell divisions in pericycle cells adjacent to the xylem poles. These founder cells re-enter the cell cycle, forming a dome-shaped primordium that emerges through the cortex and epidermis.

Option Breakdown

Pericycle (Correct)

The pericycle, a meristematic layer between the endodermis and vascular tissue, dedifferentiates to produce lateral root primordia. Auxin signaling triggers periclinal and anticlinal divisions, leading to organized cell layers in the primordium.

Endodermis (Incorrect)

The endodermis, the innermost cortex layer with Casparian strips, controls radial transport but does not initiate lateral roots. It overlays the pericycle and must rupture for primordia emergence.​

Ectodermis (Incorrect)

Ectodermis is not a standard plant root tissue; it may confuse with epidermis (outermost layer) or ectoderm (animal term). Neither forms root primordia.​

Xylem (Incorrect)

Xylem conducts water and provides structural support but lacks meristematic potential for primordia formation. Pericycle cells align opposite xylem poles, but xylem itself does not originate them.

Biological Significance

Lateral roots from pericycle enhance root branching, adapting to soil conditions via auxin-regulated development. This endogenous origin ensures precise control over root architecture.