The ratio of red light (R) to far-red light (FR) varies remarkably in different environments. This ratio can be defined as follows:

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#Unit 5. Developmental Biology

A totipotent stem cell can generate all cell types of both embryonic and extraembryonic lineages. 

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#Unit 5. Developmental Biology

The niche employs a variety of mechanisms of cell-to-cell communication to regulate the quiescent, proliferative, and differentiative states of the resident stem cell.

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#Unit 5. Developmental Biology

The shoot apical and root apical meristems provide a continuous source of totipotent stem cells for a plant to generate a majority of its aerial and ground tissues throughout life.

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#Unit 5. Developmental Biology

When a multipotent stem cell divides asymmetrically, its maturing daughter cell often goes through a transition stage as a progenitor or transit-amplifying cell.

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#Unit 5. Developmental Biology

Precursor cell (or simply precursors), is widely used to denote any ancestral cell type (either stem cell or progenitor cell) of a particular lineage.

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#Unit 5. Developmental Biology

Inner cell mass (ICM) cells of the mouse blastocyst are maintained in a pluripotent state through E-cadherin interactions with trophectoderm cells that activate the Hippo kinase cascade and repress the function of Yap/Taz as transcriptional regulators of Cdx2.