Plant roots are partially permeable. It absorbs water from soil including the essential nutrients and kick out microbes and other impurities. Assuming the plant source is not poisonous and has the cabability to store spare water. Then it is regarded as clean and safe to drink. Perhaps, good for human health too!
As of writing this, I only know three plants containing sealed and clean drinking water.
Coconut. It is the most popular. Perhaps every man living in this world knows how it taste. Climb the tall coconut tree when your in a coconut farm or ask someone to get it for you. Buy it from a push cart vendor. Or order a nicely prepared buko juice from a high class restaurant.
It is claimed that drinking young coconut water is good for relieving urinary track infection. It is identical to human blood plasma and was being used for emergency blood transfusion during wars.
Bamboo. Getting drinking water from bamboo is a survival option while in forest adventure or mountain climbing. Other options are bringing clean drinking water, looking for coconut tree and searching clean spring. Bamboo water is clean and clear if the stalk itself is healthy. Beware: damaged bamboo stalk may contain discolored and bad smelling water.
Pitcher plant. Perhaps the most rare. Recently featured on Jessica Soho. Two men got the immature and sealed pitcher. Opened it and drank the water inside. They said it is good for treating stomach pain and related ailments. Never sure if the two were suffering any disease.
I was a bit confused. As the pitcher mature, it gains the ability to produce acids to digest trapped insects.