Skip to main page content
Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
, 1 (6), 296-304

The Root Apex of Arabidopsis Thaliana Consists of Four Distinct Zones of Growth Activities: Meristematic Zone, Transition Zone, Fast Elongation Zone and Growth Terminating Zone

Affiliations

The Root Apex of Arabidopsis Thaliana Consists of Four Distinct Zones of Growth Activities: Meristematic Zone, Transition Zone, Fast Elongation Zone and Growth Terminating Zone

Jean-Pierre Verbelen et al. Plant Signal Behav.

Abstract

In the growing apex of Arabidopsis thaliana primary roots, cells proceed through four distinct phases of cellular activities. These zones and their boundaries can be well defined based on their characteristic cellular activities. The meristematic zone comprises, and is limited to, all cells that undergo mitotic divisions. Detailed in vivo analysis of transgenic lines reveals that, in the Columbia-0 ecotype, the meristem stretches up to 200 microm away from the junction between root and root cap (RCJ). In the transition zone, 200 to about 520 microm away from the RCJ, cells undergo physiological changes as they prepare for their fast elongation. Upon entering the transition zone, they progressively develop a central vacuole, polarize the cytoskeleton and remodel their cell walls. Cells grow slowly during this transition: it takes ten hours to triplicate cell length from 8.5 to about 35 microm in the trichoblast cell files. In the fast elongation zone, which covers the zone from 520 to about 850 microm from the RCJ, cell length quadruplicates to about 140 microm in only two hours. This is accompanied by drastic and specific cell wall alterations. Finally, root hairs fully develop in the growth terminating zone, where root cells undergo a minor elongation to reach their mature lengths.

Keywords: Arabidopsis; cytoskeleton; development; differentiation zone; elongation zone; growth; growth terminating zone; meristem; root apex; transition zone.

Figures

Figure 1
Figure 1
Confocal picture of a propidium iodide staining of a five-day-old Arabidopsis root (Col-0). This in vivo staining marks cell walls of plant cells. The star marks the basal limit of meristem, the arrow marks the youngest trichoblast showing root hair bulging while the arrowhead points to the onset of the fast elongation zone. Scale bar = 100 µm.
Figure 2
Figure 2
Picture is taken and adapted from the Ishikawa ands Evans (1997). It shows a nice longitudinal median section through an Arabidopsis root. The border between the apical meristem (in red) and the transition zone (in yellow) is marked with an arrow. The root cap junction (RCJ) is marked as well. Note that the lateral root cap cell layer covers both the meristem and the transition zone which ends close to the basal border of this root apex section.
Figure 3
Figure 3
Confocal picture of a fluorescein diacetate (FDA) staining of a five-day-old Arabidopsis root. The vacuoles (black) are detected by staining the cytoplasm with this viability-stain. The lower asterisk marks cells in the distal end of the transition zone, void of vacuoles, the upper asterisk points to a cell with clearly visible but not expanded vacuoles. The arrow marks the youngest trichoblast showing root hair bulging while the arrowhead indicates the onset of the fast elongation zone. Scale bar = 100 µm.
Figure 4
Figure 4
Schematic depiction of growth zones in control root apex (A), gravistimulated root apex (B) and root apex exposed to the F-actin depolymerizing agent latrunculin B (C) for several hours. The transition zone responds differentially in the gravistimulated root apex when it gets shorter in the upper part and longer at the lower part of the root apex. In F-actin devoid root apex, cells at the basal border fail to enter the zone of fast cell elongation but new cells are supplied from the apical meristem. Roots are growing very slowly and the transition zone expands basally. For more details see references 11 and 95.

Similar articles

See all similar articles

Cited by 94 PubMed Central articles

See all "Cited by" articles

LinkOut - more resources

Feedback