Can dehydration cause postural orthoststic tachycardia syndrome?

No: Dehydration can cause postural/orthostatic tachycardia and hypotension which would be similar findings associated with pots. Pots however is not caused by dehydration, but dysfunction of the autonomic nervous system.

Dehydration effects: Dehydration can certainly cause the symptoms in your question. It depends on how severely dehydrated the person was whether or not the person will have those symptoms.