Image: tip of the growing onion root. Section stained with acetic orcein, 10 µm thick.
Caliptra: it is the structure that covers and protects the root meristem during the growing of the root through the soil.
Quiescent center: it is a group of cell with very low proliferation activity. Quiescent center is thought of as the niche of the root meristem stem cells or initial cells.
Root meristem: it is the primary meristem of the root. The root meristem contains initial cells around the quiescent center that divide to lead a new cell population with a high proliferative activity, forming the proliferation region of the root. All the cell types and tissues of the root axis, as well as the caliptra cells, are formed from the root meristem.
Proliferation region: it is the region of the root meristem where cells derived from the initial cells proliferate at a high rate. After that, these cells stop dividing and elongation and differentiation begin.
Mitosis: it is the phase of the cell cycle where the DNA is condensed into chromosomes, which segregate in two equal groups that form the nuclei of the two daughter cells.
Prophase: it is the phase of the mitosis where the chromatin is condensed, and the nuclear envelope is disorganized.
Metaphase: it is the phase of the mitosis where the chromosomes are lined up in the equator of the mitotic spindle.
Anaphase: it is the phase of the mitosis where sister chromatids of each chromosome are separated from each other and are dragged toward the opposite spindle poles.
Telophase: it is the phase of the mitosis where the two groups of sister chromatids (now chromosomes) are decondensed to form the chromatin of the two daughter cells nuclei.