- Transpiration -- the evaporative cooler
for plants. Water enters plants through their roots and
evaporates through their leaves cooling the plant in the process. If
water evaporates through the plants leaves faster than it is taken
up by its roots, plants wilt as in the picture at the right. Without
enough water plants become limp, the foliage turns yellow, and the
plants become stunted as in the picture at the lower right.
- Water delivers nutrients to the plant.
Moisture in the soil holds soluble nutrients, the only form
of food that plant roots can use. This is the major way that plants
get nitrogen and the only way they get phosphorus and sulfur.
- Water in the soil is a life support for
micro-organisms beneficial to plants.