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Why does extensin cross-linking happen when plant cell growth stops?
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Cell wall
Cutaway drawing of a plant cell, showing the cell wall and internal organelles.
Extensin cross-linking occurs when plant cell growth stops to help the cell regulate its ultimate size.12
Extensin molecules are rod-shaped glycoproteins that resemble bottle brushes. These molecules are secreted into the cell wall toward the end of primary-wall formation. When cell growth ceases, specific enzymes catalyze the covalent cross-linking of these extensin molecules into a rigid mesh. By controlling the timing of this cross-linking process, the plant cell effectively determines its final dimensions.12