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.
1 At this point, your puppy can only hold his bladder for around 2 hours. It is also the best time to start housebreaking.  At 16 weeks, a puppy can usually hold his bladder for up to four hours. Prior to this, the bladder can withstand about 2 hours before the puppy must go.