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.
This is also the age at which most puppies are able to be separated from their mothers. As a general rule of thumb, puppies can hold their bladders for one hour per month of age, plus an hour. So at 8 weeks old, or about 2 months, your puppy can hold her bladder for approximately three hours, max. Take your pup outside on a leash to a certain spot in the yard so she can do her business. Take her to the same area every time.