Like humans and animals, plants need both water and nutrients (food) to survive. Most all plants use water to carry moisture and nutrients back and forth between the roots and leaves. Water, as well as nutrients, is normally taken up through the roots from the soil.
So, for example, a 3-month old puppy should be able to hold its urine for approximately 4 hours in a pinch. This means that if you have a properly toilet trained 4-month-old puppy that, theoretically, can hold its urine for 5 hours, and you shut that puppy in a crate for 6 or 7 hours, you are courting disaster.
Potty training a puppy at night. Puppies vary in how long they can last at night without a wee. Many pups are nine or ten weeks old before they can last all night (say around midnight until 6 or 7 am) without a wee. Some pups are even older and a few pups can last six or seven hours from around eight weeks old.