The strongest component of the cell wall<span> is a carbohydrate called cellulose, a polymer of glucose. The </span>cell wall gives rigidity<span> and strength to the </span>plant cells<span> which offers protection against mechanical stress. ... The </span>rigidity<span> of primary </span>plant<span> tissues is due to turgor pressure and not from rigid </span>cell walls<span>.</span>
<span>The oldest known vascular plants in the northern hemisphere are Devonian
This is true</span>
