elongatiezone

The elongatiezone, or elongation zone, is a region in plant roots where newly produced cells cease division and increase in length. It lies between the meristematic zone (cell division) and the differentiation zone (where cells acquire specialized forms). The elongation zone is typically located a short distance behind the root tip, with size varying among species and environmental conditions.

Cells in this zone expand primarily by turgor-driven enlargement as their walls loosen. The acid growth hypothesis states that auxin triggers proton pumps, acidifying the cell wall and activating expansins that loosen the cellulose-hemicellulose network, allowing water uptake and cell expansion. Cell walls are remodeled while microfibril orientation guides the direction of elongation. Cell-wall synthesis continues but elongation is the dominant process.

Functions and regulation: The elongation zone contributes to primary root growth by increasing cell length, lengthening the root. Growth rate responds to environmental factors such as soil moisture, temperature, and nutrient availability, and to hormonal signals including auxin, gibberellins, and cytokinins. High elongation rates promote deeper rooting, while low rates limit penetration. Species-specific differences are common.

As cells exit the elongation zone, they enter the differentiation zone, where they mature into tissues such as epidermis, cortex, endodermis, and vascular tissue, forming the mature root.