One type of density change is mass over volume.
<span>Plants without vascular system are non-vascular plants. Non-vascular plants have no xylem and no phloem.
Non-vascular plants include algae, bryophytes, moss grass, liverworts and hornworts.
The answer to this item is moss. Moss is a non-vascular plant which has no seeds and no flowers. It uses spores in reproduction.</span>
<span>Sodium channels close when not occupied
</span><span>Sodium ions diffuse through and enter the cell.
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Then they leave the cell.
The sodium diverts in the cell layer have receptor locales for acetylcholine.
