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Cell Walls-Primary and Secondary

With very few exceptions, plant cells always form cell walls. The cell walls contains layers of cellulose fibers interspersed within a hemicellulose packing. Together, these substances yield a very strong but pliable supportive layer for plant cells. Adjacent cell walls are cemented together by botanic "glues" or pectins in a layer called the middle lamella.

The cell wall forms outside the plasma membrane initially as a thin primary cell wall. Thereafter, the primary cell wall may thicken or a more durable secondary cell wall can form between the primary cell wall and plasma membrane.

Plant cells remain in contact with one another via plasmodesmata, membrane lined channels that extend through cell walls to link adjacent cells. Plasmodesmata facilitate intercellular communication and transport.

Now, roll over the most central plasmodesmata in the diagram.